Page 1 of 3 123 LastLast
Results 1 to 25 of 54

Thread: Misfire when cold, and high CO and lambda during inspection

  1. #1
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i

    Misfire when cold, and high CO and lambda [~ -40 additive fuel trim]

    Today I just, and really just passed the yearly inspection (ITV in Spain)..
    CO (carbon monoxide) was too high at 0.55% and Lambda at 1.05 but luckily the technician asked me to raise the RPM's to 3000 rpm and keep it there. And slowly the values started to improve, but only after he asked me to go to 3500 rpm and waiting a few minutes, the values went in the green zone.. CO dropped to close to zero and lambda to 1.01-1.02 if I'm correct. Note: the car was warmed up before I entered the inspection, but it seemingly needed to burn off some stuff and heat up a lot more before the combustion turned okay.. It was burning too rich and/or was having misfires (which it felt like, it didn't feel 6 cylinder smooth).

    I already noticed that at cold starts the engine would stumble at 5 (or maybe even 4) cylinders for quite a while until it would warm up.. On other (warmer?) days it would be okay from the start.. It also happens more often if I haven't driven the car for 2 or more days..

    A year ago I already replaced all spark plugs and I also bought a new coil and a couple used coils and I found two cylinders that performed poorly. Changing coils and plugs improved things somewhat, but it's still not perfect. The problems seem related to 1 or 2 cylinders. The M52B25 doesn't run as smoothly as the older M50 I used to have (E34 525i).. I also already replaced the MAF sensor, and the car has an exhaust from the E36 328i. Last year it passed the inspection directly with no problems.

    I have no errors in DISA.

    So, I'm thinking about compression problems.. Perhaps the piston rings are a bit stuck when the engine is cold? The car, when I bought it in January 2016 had been unused for over a year (or perhaps even 2 years), which is not so good for the piston rings I suppose. So, today I bought a cheap compression tester from Ebay which will arrive in a week.. Let's see what I find.
    Another candidate could be the fuel injectors, but I don't know how that would improve when the engine would warm up more?

    Any experience/tips you can give me.. Much appreciated. Thank you!

    Cheers Ed (from the Spanish Canary Island Tenerife)
    Last edited by ed323i; 05-20-2018 at 01:12 PM.

  2. #2
    Join Date
    Jun 2010
    Location
    NY
    Posts
    9,079
    My Cars
    1997 328i
    Check for vacuum leaks. If your oxygen sensor is original or very old then it should be replaced. You can get a brand new set of ignition coils off ebay for little money.

    When you remove spark plugs you should keep them in order to see if one has issues for that particular cylinder.
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
    Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".

  3. #3
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Thanks.. I'll go and check.. I'll do the compression test too.. Let you know the results.. Cheers.

  4. #4
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Finally managed to do the compression test..
    Yesterday I did the test with a cheap-o Ebay analog meter (this one), and alas the rubber tube lost/leaked pressure some where, so I asked someone to start for me and I pressed the univeral metal tube (with rubber on the end) in the 6 spark plug sockets.. Results were scary:
    1: 3 bar = 44 psi
    2: 7 bar = 102 psi
    3: 7 bar = 102 psi
    4: 4 bar = 58 psi
    5: 7 bar = 102 psi
    6: 3 bar = 44 psi

    Really scary, but I couldn't believe it because the engine has a lot of power, must be close to 190-200 crank HP (with the chip and 328i exhaust)..

    So, today I visited a car parts store and decided to buy a 95 euro Bahco BE5400P digital compression meter (this one). Immediately I noticed the better build quality.
    Next was the test (engine warmed up, depressing gas pedal while cranking, 8 cranks), and I was very, very happy with the results:
    1: 10.8 bar = 157 psi
    2: 11.15 bar = 162 psi
    3: 11.0 bar = 160 psi
    4: 10.9 bar = 158 psi
    5: 10.85 bar = 157 psi
    6: 11.05 bar = 160 psi

    This all at 100 meters altitude (+/- 300 feet; you can add +2 psi to compensate for this).. And the engine has 270,000 kilometers (168,000 miles).
    Specs for the M52B25 at sea level is 10-11 bar (145-160 psi). The compression of the M52B25 cylinders is specified at 10.5 bar, 152 psi (source).

    The Bahco meter is really good and at retests gave the exact same results.. Impressive. The cheap ebay meter gave different results every time.

    So, after going to bed yesterday, feeling really scared, and already looking at good offers for used engines, I am thrilled to see that everything seems fine.
    In the morning I had already tested for blowby, by taking off the CCV hose, and both at idle and at 3000rpm I couldn't feel any blowby, so I already thought: OK, the pistons and piston rings seem fine (and hence thought that the head or head gasket would be dead). Is it normal for the engine to start misfiring and stumbling once the CCV hose is disconnected from the head (near the Vanos)? Or should the diaphragm be closed at that point and it shouldn't introduce false air into the intake manifold?

    But with these values, I think I can rest assured that both the engine block/cylinders and the head and head gasket are in good order..

    I already re-checked all ignition coils (disconnecting them one by one), and all 6 of them seem to work fine (disconnecting them led to more misfires for all 6 cylinders).

    So, like you wrote before, now I just have to find the vacuum leak :-) (I did some simple checks and most rubbers seem okay and connected properly)..

    Cheers, Ed

    P.S. One tip: Do not buy the cheap ass analog compression meters from Ebay, but buy a digital one from a quality brand. Be assured that you can use it a lot of times in your life, also when buying another car.
    Last edited by ed323i; 03-21-2018 at 02:32 PM.

  5. #5
    Join Date
    Jul 2010
    Location
    Murrieta, CA
    Posts
    9,530
    My Cars
    '94 325iC, '08 328i, E93
    Based on the El Cheapo compression tester, you need a complete engine rebuild. Based on the good compression tester, your engine is in great shape.

    I think your diagnostics should lead you to the CATs as a problem. I'm not saying that your CATs are bad, I just think this is where you will be at the end of this. You have significant data to collect first to isolate other sources of trouble.

  6. #6
    Join Date
    Jul 2010
    Location
    Murrieta, CA
    Posts
    9,530
    My Cars
    '94 325iC, '08 328i, E93
    My idea is that you may have crap gas that has taken the CATs out. I'm not sure how you can test for this. Seems like the smog guy should be a helpful resource. I live in California, the test they do here is in two speed ranges. The car can pass one speed range and fail the other. One thing that affects the performance of a poor CAT is heat. More heat makes them work better. This explains why you put the engine at 3500 and the readings improved.

  7. #7
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Thanks.. I bought the car in Februari 2016 with a new 230 euro aftermarket CAT (because it failed the tests) that was welded in the original 323i exhaust. It died after one year.. I think the welds weren't perfect and oxygen could enter which caused combustion inside the CAT, and soon the internals of the CAT were lost (I will open it up some day soon to check, but it feels and sounds like it's empty or at least loose membrames)..

    Then I was very lucky to find an E36 328i exhaust from front to back (two pipes all the way, whereas 323i exhaust = 320i exhaust = 2 pipes until CAT, and only 1 after CAT). Installed it, and it worked flawlessly. Passed the tests perfectly. And as a bonus better sound and more power.

    Then, exactly one year later (Jan 2018), it almost failed the tests.. It might be the 328i CAT was already quite old, but, because the engine just doesn't run as smooth as an M50/M52/M54 should do (too much vibration, especially when cold, then there are real misfires and lots of vibration).. It never runs as smooth as my previous several M50s did, while the M52 ECU is a lot more advanced and it should run even better than the M50 I think..

    Well, the compression can't be the problem.. Spark plugs were already changed. Ignition coils are okay I think. So I will check for vacuum leaks, and the oxygen sensors might perhaps be a problem.

    But, it might just be I have bad luck and the CAT is also quite old already (or it's having a hard time with a probably too rich mixture, which also slowly kills the CAT)... We'll see..

    It would be good to go to a test center and then watch the live INPA oxygen sensor and fuel values while monitoring the real exhaust gases.. It would be even better if I could monitor the real gases before it enters the CAT.

    Cheers Ed
    Last edited by ed323i; 03-21-2018 at 03:08 PM.

  8. #8
    Join Date
    Jul 2010
    Location
    Murrieta, CA
    Posts
    9,530
    My Cars
    '94 325iC, '08 328i, E93
    You can monitor the exhaust before and after the CATs. That's what the O2 Sensors do. You are not going to run out and buy a GT1 Diagnostic package because it runs to a few thousand dollars (USD), but if you can find a local BMW service center that has the package, it will tell you exactly what you want to know. I don't know that INPA will tell you this. I might be wrong, but I think you need a better package than you can easily buy.

  9. #9
    Join Date
    Jul 2010
    Location
    Murrieta, CA
    Posts
    9,530
    My Cars
    '94 325iC, '08 328i, E93
    And, if you have bad gas -- contains lead -- then the CATs will be killed very quickly. And, if your car is running rich, this will also kill the CATs.

    I also have concerns about used coils. Something that's more important than the "right" coil is a complete set of balanced coils. If you have a coil that is not providing a strong spark, then you are getting a partial combustion and this can put raw fuel into the CATs, raw fuel is bad. You should invest in a set of coils that are all the same, and you may as well use a fresh set of spark plugs.

    It seems like you should have the Check Engine light with codes for various misfires, but you have a euro-spec car and I don't know what the application schedule of the OBD II system is for you. You could be having issues that the computer is not telling you about because of the cut-in date of applying the OBD II specification to Europe.

  10. #10
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Thanks.. I meant that I would go to some sort of test center where they would hook up the car to a wideband lambda sensor. And here it would be interesting if they could also measure before the CAT. Just to confirm if my O2 sensors are giving the right values and the ECU is enriching correctly (which I can monitor through INPA).

    So, then I would have:
    * INPA to monitor the narrow band O2 sensors before CAT (my E36 doesn't have post-cat sensors) and what the ECU does with this info
    * The service/test center to tell me what exactly happens after the CAT

    Or, what I also could do, based on my experience with megasquirt + wideband O2 sensor (on my E28 528i, which went like a rocket after being properly tuned by myself, 6 coils, AFM delete, digital spark control): just buy a wideband O2 sensor kit (with controller and gauge), plug it in one of the O2 sensor sockets in the exhaust manifold, and then let the ECU use the narrow band O2 sensor in the other bank (which I hope it will extrapolate to the bank with the wideband; or, most wideband controllers also offer a simulated narrow band output which I could then connect to the BMW ECU). Connect the wideband O2 sensor controller to my laptop or other A/F ratio viewer, and then I would also be able to see what's going on. Such a kit can be bought for a little more than $100, so that could also be an option.. At a BMW service center you would loose that kind of money in a blink of an eye ;-) .. (even here in one of the poorest provinces of Spain, they ask 75 euro ex VAT per hour for normal mechanical work)

    (or I could drill another hole in the exhaust, before the CAT, weld in a socket and the screw the O2 sensor in there)..

    - - - Updated - - -

    In Europe there is no Check Engine light.. But with INPA you can monitor all errors and faults and strange fuel values. These all seemed okay when I checked half a year ago, but I'll check again.. The one thing I can't check with INPA alone is if the oxygen sensors are functioning properly. They sure seem to be working fine and give normal values, oscillating frequently between rich and poor mixture values like they should. But there is no way to be sure without monitoring the exhaust gases with a wide band oxygen sensor.
    Last edited by ed323i; 03-21-2018 at 04:28 PM.

  11. #11
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Thanks for the tip about the coils.. I'll give them another check, visually checking the spark quality.
    What I did last year, was buy a new coil, and the one by one check all the coils by replacing them one-by-one with the new coil, to see if the vibrations decrease. I was then able to isolate one bad one, which I replaced with the new coil. The other coils all seemed perfectly fine (the vibrations wouldn't decrease in the least when replacing them with the new coil).

    Perhaps I'll buy two new ones, and repeat the procedure, to see if I can isolate another one or two bad coils.
    Last edited by ed323i; 03-21-2018 at 05:13 PM.

  12. #12
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    This morning, I tested again, with the engine completely cold (+/- 17 degrees C) and these were the results.. Even a little better than yesterday with the warmed up engine:
    1: 11.15 bar = 162 psi
    2: 11.25 bar = 163 psi
    3: 11.2 bar = 162 psi
    4: 11.2 bar = 162 psi
    5: 10.85 bar = 157 psi
    6: 11.05 bar = 160 psi

    So, both with the engine cold and warm, the results are outstanding, especially with this mileage (almost 170,000 miles).

    I will be checking:
    * The coils
    * The oxygen sensors
    * Vacuum leaks

    It will take some time, but in the end the engine should be able to run very smoothly, with these compression values, and also no observable blowby.

    Last Monday I ordered a lot of parts (4 Bilstein shock absorbers, Meyle HD control arms front, and a lot more suspension parts; a complete suspension revision), and when I thought the engine was ready for the junk jard a day later (and unable to cancel the orders) I freaked out a bit.. But luckily everything seems in order, and I'll upgrade the E36 soon once all the parts arrive.

    Anybody has experience with Lucas oxygen sensors.. The M50TU and M52 (non-TU) uses Titania type oxygen sensors (M50, M52TU and M54 use Zircania type, a lot cheaper) and these are expensive, like 100 euro a piece. But I found a really nice offer on Ebay (here it is). Seems tempting, but I don't know if the Lucas oxygen sensors are any good/reliable..

  13. #13
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Interesting new observation:
    After reinstalling the spark plugs, coils, plastic covers, fuse 18 and the ECU relay, I started the car and the engine was having a really hard time to stay running and there was a lot of vibration. A bit later I took it for a spin and eventually it ran quite okay..

    I think that the ECU must have reset the adaptation values, and then it seems that the stock injection values are not working very well with the engine as it is now.. At that point, with the engine and oxygen sensors cold, we can take the oxygen sensors out of the equation, because they are not working when the engine is cold. So, the most logical explanation is a relatively big vacuum leak, which makes it impossible for the ECU to determine the right injection times (MAF giving too low air flow values, so the ECU ordering the injectors to inject fuel, not based on what mass of air actually enters the cylinders, i.e. more air than what is metered)...

    I'm getting there.. Perhaps I'll remove the intake manifold completely and inspect all hoses and clamps carefully. First I'll double check if I can find anything by just feeling and looking below the manifold. The big rubber hose between the throttle body and MAF sensor seems in perfect shape.

  14. #14
    Join Date
    Apr 2005
    Location
    Tampa, FL
    Posts
    3,377
    My Cars
    97 E36M3 S54
    If you have a buddy with the same engine try swapping the engine ECU/DME, they can go bad and lead you down the wrong direction too.

  15. #15
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Thanks for the tip.. I already changed the ECU/DME for a chipped one a little more than half a year ago (which btw is a truly great upgrade for the factory down-tuned M52) and there was no change in the symptoms.. So I think that probably rules out the ECU..

    Oh wait, there could be one more explanation.. The fuel pressure (or theoretically the injectors, but it would be very strange if all/most of them were bad). The ECU assumes that the fuel pressure is right (that a millisecond of injection time results in a specific amount of fuel being injected) and that the MAF gives accurate values to correctly calculate the injector times.

    So, wrong fuel pressure and/or vacuum leaks are the most likely causes I think.. One or more coils could also still be bad, but those shouldn't mess up the running with factory values so much, especially since it recovers quickly after adapting. I'll hook up INPA soon to see how the adaptation values change after clearing/resetting the adaptation values.
    Last edited by ed323i; 03-22-2018 at 11:09 AM.

  16. #16
    Join Date
    Jul 2010
    Location
    Murrieta, CA
    Posts
    9,530
    My Cars
    '94 325iC, '08 328i, E93
    Quote Originally Posted by ed323i View Post
    Interesting new observation:
    After reinstalling the spark plugs, coils, plastic covers, fuse 18 and the ECU relay, I started the car and the engine was having a really hard time to stay running and there was a lot of vibration. A bit later I took it for a spin and eventually it ran quite okay..

    I think that the ECU must have reset the adaptation values, and then it seems that the stock injection values are not working very well with the engine as it is now.. At that point, with the engine and oxygen sensors cold, we can take the oxygen sensors out of the equation, because they are not working when the engine is cold. So, the most logical explanation is a relatively big vacuum leak, which makes it impossible for the ECU to determine the right injection times (MAF giving too low air flow values, so the ECU ordering the injectors to inject fuel, not based on what mass of air actually enters the cylinders, i.e. more air than what is metered)...

    I'm getting there.. Perhaps I'll remove the intake manifold completely and inspect all hoses and clamps carefully. First I'll double check if I can find anything by just feeling and looking below the manifold. The big rubber hose between the throttle body and MAF sensor seems in perfect shape.

    This is actually a huge problem. The cracks happen at the folds in the rubber and are very difficult to see. Smart money would take this off and do a careful inspection with a flashlight. If you break it taking it off, it was probably broken already.

    It will give LEAN Codes, P0171 and P0174.

  17. #17
    Join Date
    Jul 2010
    Location
    Murrieta, CA
    Posts
    9,530
    My Cars
    '94 325iC, '08 328i, E93
    You're touching on a possible issue with the MAF. If the MAF is lying about the air temp/density (mass), then the computer can reduce fuel if the lie is that the air is thin. The goal is to obtain an air fuel ratio of 14.7:1, this goal is more for the health and well being of the CAT than of the engine, but whatever. If the intake is thought to be thin, then less fuel will be called for -- sent through the injectors (injector timing will be reduced) -- causing the engine to run poorly. Having said that, this to would give a lean condition, and it goes somewhat against the normal MAF failures that we see. If the MAF is lying about the air mass, reports thin air, when the air mass is actually normal or dense, then you can see a lean condition, P0171 & P0174.

    Normally, the MAF failure will be such that the air mass is reported as dense one second then thin the next, and back and forth several times in a minute. The result is that the O2 Sensors see the changes in the fuel delivery (injector timing) and the trouble code that gets reported is not RICH or LEAN, but MALFUNCTION. There are generic OBD II Codes, P0170 and P0173 that define MALFUNCTION, and there are unique codes, P1188 and P1189 that also define MALFUNCTION. The P0 and P1 codes are a little bit different, one is FUEL TRIM MALFUNCTION the other is FUEL CONTROL MALFUNCTION. I forget which is which, but both mean the same thing to me. It would be atypical for your MAF to fail in a way that the fuel ratios went to one extreme or the other and remained there, and if this happened you would get a rich or lean code depending upon the extreme that was hit. My MAF failed where both limits were being hit, I was shown the malfunction codes, P1188 & P1189.

    Your compression numbers are good. I believe the goal is to test compression on a warm engine, not a cold one, but your numbers, cold and warm, are well within the range of expected results.
    Last edited by JDStrickland; 03-22-2018 at 02:08 PM.

  18. #18
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Thanks again.. Will look into it.. Will also connect INPA and check the inlet air temperature and coolant temperature, which also affect the fuel calculations.
    Will let you know the results tomorrow or the day after.

    So these are the most likely candidates:
    * Vacuum leak (smoke test, checking all rubbers and clips)
    * MAF sensor (INPA check, and see if it runs better without MAF, and if possible use other MAF sensor)
    * IAT Inlet Air temperature sensor (easily checked with live INPA values)
    * Coolant temperature sensor (easily checked with live INPA values)
    * Fuel pressure (fuel pressure meter needs to be hooked up, bit difficult)
    Last edited by ed323i; 03-22-2018 at 02:35 PM.

  19. #19
    Join Date
    Jul 2010
    Location
    Murrieta, CA
    Posts
    9,530
    My Cars
    '94 325iC, '08 328i, E93
    Fuel Pressure comes off of the fuel rail, it should not be hard to get this. In the realm of fuel pressure, you have considerations of the fuel pump and the fuel pressure regulator. My pump in my X5 crapped out while sitting at a light, the light turned green and the pump died when I applied throttle. No warning at all, just up and quit working from one moment to the next.

    We talked about OBD II, right? You have a euro spec car so your market plays a role in the application of the specification. All cars offered for sale in the USA had to be OBD II Compliant for the '96 Model Year and beyond. To be compliant, the Check Engine Light must come on before engine start, then go out when the engine is running. Fail to come on is a fault, fail to go off is a fault. Your car runs poorly, the Check Engine light should be on when the engine is running. But, again, your market is different. If you have an OBD II Data Port above the area where the clutch pedal would be, or is, then you should see if it has any vital information to spit out.

  20. #20
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    While Megasquirting the E28 528i, the fuel pressure regulator died on me, and it took a while to diagnose.. It caused fuel pressure to rise to 6-7 bar, which caused such a rich mixture that the car wouldn't start anymore.. I don't think it happens often, but it happens once in a while. It can also cause a too low pressure, causing the car to run too lean. With the E28 M30 I could just take the normal fuel hose off the rail, put the pressure meter in between, and I could read it. But with the M52 and later BMW's the fuel hoses have special connectors I think, and it's not so easy to plug a meter in between.. Or perhaps it has a special connector for just that on the rail itself? Will check it out..

    Yes, correct.. As of the M52 (more or less) all BMW's in Europe are OBD II.. But they don't need to have the check engine light (and my 1997 E36 doesn't have it, but the ECU does send out a signal to light up a bulb if I would connect it). With INPA I can read all error codes, all adaptation values, live injector times, oxygen sensor values, Vanos angle, everything.. Even better than most OBD II readers can do.. So I'll do that to start with. There is no OBD II port near the clutch pedal, but I can use the 20 pin BMW diagnostics connector next to the engine (and also guide the USB cable through the passenger window and log while driving if needed)..

    Update: There indeed is a special 'schrader valve' connector for testing the fuel pressure as you can see here, although this is an M52TU: https://www.youtube.com/watch?v=dU2olxmfo-U and here is the M52 shrader valve: https://www.bimmerforums.com/forum/s...-angle-adapter .

    Update 2: I'll be using my vacuum cleaner to test for vacuum leaks.. Here are the instructions: http://www.bimmerfest.com/forums/sho....php?p=4519113 .
    Essentially: connecting a garden hose to your VAC, sealing off the MAF with plastic bag and duct tape (and perhaps also the exhaust pipe with tennis balls or also bag+tape if one cylinder is at TDC with both valves open), and connecting the garden hose to the brake booster connector on the intake manifold. Then listening carefully for leaks, using a stethoscope. Best to move the VAC as far away and behind a door so it doesn't make too much noise. The first thing I'll do though is connecting the laptop with INPA to see what comes up.
    Last edited by ed323i; 03-22-2018 at 09:42 PM.

  21. #21
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    OK.. Today I hooked up my laptop with INPA.. Coolant and air intake temperature sensors all fine. TPS all fine (can be monitored live). No errors for the MAF, no lean error codes, no error codes whatsoever. But I saw that the adaptation values were quite high. +32 for the fuel enrichment in one bank. So it seems taking off the ECU relay doesn't reset the ECU adaptation values (which, if it would do so I considered a bit odd).

    When I started the car, the car started to smell like unburnt fuel quite quickly and the engine ran very poorly, lots of vibrations..
    Then I rechecked every cylinder by disconnecting every coil one by one and every cylinder reacted (the engine started to run even worse, and immediately ran a bit better after reconnecting)..

    Then I turned the engine off (to make sure it wouldn't warm up too much, making cold-start diagnosis impossible).

    Next, I resetted the adaptation values.. And I restarted the car, and, it ran a lot better immediately. Then I took it for a spin, and it runs marvelously on the factory settings. Faster and more nimble than before I would say.

    Later, I reconnected INPA, but the adaptation figures were still at zero, so the ECU needs more sampling time to adjust those.

    So, what I think now is that one of the 2 (pre-cat) oxygen sensors is wasted and is showing too lean figures to the ECU, which then adjusts by injecting more fuel. When the engine is warm, it runs a bit rich, but it won't really affect the running quality.. But when the car is cold, and the ECU is already enriching a lot, combined with the adaptation figures, the mixture gets too rich and it runs poorly when cold. Stupid me didn't write down the exact adaptation figures for each bank.. But I believe I saw +32 for bank 1 and +/- a single digit number for bank 2.

    So, what I'll do is just drive the car a few days, then, once it starts to show problems (running poorly after cold start) I'll reconnect the INPA and see what the adaptation values are on, and which bank.. Then I'll reset the adaptation figures again and disconnect the suspect oxygen sensor. I believe the ECU will now run on just the oxygen sensor of the other bank, and extrapolate the fuel calculations to the bank with the disconnected O2 sensor. Then I'll drive a few days more, and recheck everything.. If it keeps running fine, I'll change the suspect O2 sensor.. And hopefully that's it.. (I tried to order the 40 euro Lucas sensor, but they won't ship it here, so with the other shops asking 90-100 euro per sensor, I'll wait a bit longer, using the protocol outlined above, until I'm certain it really is the O2 sensor)..

    Or am I overlooking something here. Are there other reasons for the ECU enriching too much? Misfires would allow unburnt fuel and untouched oxygen to enter the exhaust, which would make the oxygen sensor think it's way too lean, and would make the ECU adjust the mixture to a richer one.. But then you'd get into a vicious cycle quite soon: misfires -> O2 sensor says: lean -> ECU enriches mixture -> more misfires -> etc.. Does anybody know how this works in detail?

    Thanks again for your help!

    P.S. I might still have a vacuum leak (which would cause a too lean mixture, which the ECU would correct also by enriching the mixture, but the resulting mixture, as measured at the tail pipe by a service/test center should be close to perfect, IF the oxygen sensors are working ok) or other problems going on, but I think I should now focus on this approach.
    Last edited by ed323i; 03-25-2018 at 12:16 PM.

  22. #22
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Today, I've driven a bit more, on the high way, which is perfect for the ECU to adapt the fuel injection times based on the oxygen sensors' input.

    Fuel trim (adaptation values) for bank 1 is -4 and for bank 2 is -3 (range -40 to +40). This is such a small deviation that everything seems just fine. The car also cold started just fine (when the adaptation values/fuel trim was at 0/0)..

    So it seems that somehow the adaptation values moved to a too high value and then (perhaps because of the vicious cycle; rich mixture causing misfires, which cause further enrichment of the mixture) remained there.. No sign of a vacuum leak, no sign of any error message, no sign of a defective O2 sensor (both banks virtually identical fuel trims), no sign of a defective coil or injector..

    So, let's see in the longer term if the cold start problems (high vibration due to misfires until warming up) return or not.. Until then, I'll just wait and see. If they return (which is probable), I'll check the adaptation values again to see if those help me diagnose the root of the problem.. And, it would be interesting to do a exhaust gas test to see if the CO and lambda values are right now. I do think so.

  23. #23
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    After a few hundred kilometers, the fuel trim values are as follows:

    Bank 1:
    Adaptionswert Additiv 1: -33
    Adaptionswert Multiplikativ 1: -2

    Bank 2:
    Adaptionswert Additiv 2: -27
    Adaptionswert Multiplikativ 2: -1

    Not a single error was recorded in all these kilometers.

    I'll do some research to see if these fuel trim values are normal, or if the ECU is leaning the mixture a bit much.. I'll let you know the results. At a first glance, it seems that there isn't a big difference between bank 1 and 2 (unless the -2 versus -1 multiplikativ value is a significant difference, but I don't think so).

  24. #24
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    OK, I found some very interesting information.. Before that I browsed through lots of discussion forums and people replacing *everything* (fuel pressure regulator, all coils, MAF, oxygen sensors, etc, etc) and not finding the culprit of the big negative additive values.

    Here it is:
    http://www.meeknet.co.uk/e38/Diagnostics.htm
    "Adaption Value Additive - If the Lambda Integrator reports that the mixture is too lean (at idle) then the ECU will slowly increase this value to increase the injector dwell so that the mixture enriches. If you have a value here that it greater than +10 you can be sure you have a vacuum leak - or the MAF is mis-reporting the actual air mass.If the value here moves to less than -10 (especially if combined with a negative value for the multiplicative adaptations) that usually points to a failure of the vacuum pipe that runs between the PCV and the Fuel Pressure Regulator (FPR) - at idle the PCV will be supplying a vacuum to the FPR which limits the fuel-rail pressure to 3.0 Bar - if that vacuum is missing (the pipe is kinked, torn or missing) then the fuel-rail pressure will increase to 3.5 Bar and adaptations will be seriously skewed trying to pull the fuel/air mixture back to the correct levels. A slightly negative reading indicates less than perfect combustion (plugs, coils)"

    The additive value is used at idle and low loads and the multiplicative values are used at higher loads. So, in my case the problem is at the idle and lower loads, while at higher loads there is no real problem (-1 or -2% is nothing).

    So, the ECU expects 3.0 bar at idle, and gets 3.5 bar if the vacuum hose is leaking/blocked, or perhaps the FPR itself is not reacting to high vacuum anymore (the membrame not working anymore)..

    I'm not sure how this works with the M52.. If it's connected to the PCV like with the M60/M62 E38's.. I'll check it out tomorrow and let you know the results. And if that vacuum hose seems okay, then it still might be at least 2 coils (because both banks are affected), but because both banks have virtually identical values the vacuum hose is the more logical explanation.. It's number 10 on this chart: http://www.realoem.com/bmw/enUS/show...diagId=13_1718 .

    And another detailed explanation:
    http://forum.e46fanatics.com/showthread.php?t=1105539
    Fuel Pressure & Volume Testing
    Additional note/clairfication for the M52 (323/328 models). These models utilize a manifold vacuum controlled fuel pressure regulator unlike the M54 (320/325/330 models). Bentley did not properly or clearly outline how to test the fuel pressure on the M52 (323/328 models). For the M52 (323/328 models) the 3.5 +/- 0.2 bar or 50.76 +/- 2.9 PSI fuel pressure is with the vacuum line to the Fuel Pressure Regulator disconnected. If the fuel pressure is tested with the engine running AND the fuel pressure regulator vacuum hose connected, the fuel pressure should be approximately 2.8 bar or 40 PSI> Please make note of this clarification. Recently we have seen a few M52 (323/328 models) that for some reason do not have proper intake manifold vacuum to the fuel pressure regulator causing the full fuel pressure of 3.5 +/- 0.2 bar or 50.76 +/- 2.9 PSI to be present at idle. This WILL cause the vehicles to to run Rich and have high Negative Fuel Trims. Please pay attention to this if you have a M52 (323/328 model).
    Last edited by ed323i; 04-01-2018 at 04:20 PM.

  25. #25
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    A note on the adaption aditiv and adaption multiplikativ values. On most sites they state that the additiv is meassured in miliseconds that are added (or subtracted) from the normal calculated injection times, while the multiplikativ values are in percentages.. Alas, with different engines (ECUs), they use different units.. For example, on some ECUs that multiplikativ is really shown as a factor, such that -2% on the M52 is the same as 0.98 on the other ECUs..

    Also, with other ECUs the aditiv values really seems to meassured in ms, with values like -0.08 .. But with the M52 it can't be miliseconds, because with values like -33 or even -50 (both not triggering error messages in the ECU by the way) this would be impossible, because at idle (if I correctly remember my experience with Megasquirting an E28 528i) a typical injection time is like 2ms or 4ms. Not much more. So, with the M52 the aditiv value is probably meassured in one hundreds of miliseconds. Such that an idle injection time of say 3ms gets reduced tot 2.5ms if the aditiv value is at -50.

    Also, I always thought the M52 ECU was more intelligent and would have some sort of 2D map for the fuel trim with like 100 stored adaption values.. Such that at any given RPM (horizontal axis) and any given load (vertical axis) it would have a value stored to adjust the injection timing.. Actually, in reality, it's a quite 'dumb' system, with only one additive value (mostly for idle and low loads) and one general correction factor (multiplikativ), only (sort of) differentiating between low and high loads.

    Because of that relatively 'dumb' adaption, it's obvious why the idle isn't as smooth as it should be with an M52.. At every load and every rpm the injection timing is reduced by exactly the same figure (-33 bank 1 and -27 bank 2), which results in very sub-optimal AFR at every load and rpm, causing a bad idle, misfires and vibrations. Not excessively, but very noticable.

    Okay, today I'll be checking the vacuum hose connected to the fuel pressure regulator.. If the theory is correct, I should be able to remove the vacuum hose, and plug it with my finger or a screw, and then there should be no change in the idle.. If, on the other hand, the fuel pressure is properly regulated at idle (dropping to +/- 2.8 bar instead of the regular 3.5 bar), the engine should definitely react to the increased fuel pressure (getting too rich) when I remove the vacuum hose..
    Last edited by ed323i; 04-02-2018 at 06:40 AM.

Page 1 of 3 123 LastLast

Similar Threads

  1. Replies: 5
    Last Post: 08-07-2015, 01:51 PM
  2. Replies: 3
    Last Post: 01-24-2012, 12:01 AM
  3. 520i misfiring when cold
    By pwalshe in forum 1996 - 2003 (E39)
    Replies: 6
    Last Post: 02-05-2010, 08:29 AM
  4. Misfiring when cold
    By spconner in forum 1991 - 1999 (E36)
    Replies: 0
    Last Post: 12-29-2009, 03:41 PM
  5. Misfire when cold - Air Temp Sensor
    By RSK540iA in forum 1988 - 1996 (E34)
    Replies: 18
    Last Post: 01-12-2008, 09:49 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •