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Thread: What is going on?

  1. #1
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    What is going on?

    Was driving the car home to day from work and exited the highway. Drove on surface street for about 5 minutes and stopped at the lights. All of a sudden, the idle started to stumble and the exhaust started popping like the engine was misfired.
    I pulled off the street into the parking lot, shut off the engine and popped the hood. I inspected and nothing looked out of place. I looked under the car and nothing I could see is wrong. I started the car again and it still ran like crap.

    A little bit of history: I recently replaced both O2 sensors on the car about a month ago and the car has been running a lot better; better acceleration and less fuel consumption. It was running rich and the O2 sensors were not functioning properly, hence, the replacement. The Cat converters are Magnaflows from 3 years ago with no more than 5K miles on them. I can probably safely assume that the Cats suffered the same fate as the O2 sensors due to the rich running condition. However, I have ran about 4 bottles of Catalytic Converter Cleaner prior to the O2 sensors replacement and each time, the car ran better until the O2 sensors fouled up again.

    After the O2 sensors replacement, everything has been fantastic and I actually got to enjoy the 3.91 LSD diff upgrade finally.

    The joy was short-lived as now the car runs like it's misfiring. Both exhaust runs hot so I don't think it's in Limp Home mode but there's no power (mixture is totally off). Instead of smelling rich exhaust, it now smells like a new car exhaust...rotten egg smell. That's very strange.

    What can the issue be? Are my Cats gone? Are the O2 sensors gone? I will wait until this weekend or so to troubleshoot but this is just strange.
    When my car was in LHM, it ran weak but motor was smooth. Now, it's just very lumpy and popping at the exhaust tip.

    Appreciate any help with diagnosing the problem.

    Chris

  2. #2
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    Quote Originally Posted by ChrisFuture8 View Post
    Was driving the car home to day from work and exited the highway. Drove on surface street for about 5 minutes and stopped at the lights. All of a sudden, the idle started to stumble and the exhaust started popping like the engine was misfired.
    I pulled off the street into the parking lot, shut off the engine and popped the hood. I inspected and nothing looked out of place. I looked under the car and nothing I could see is wrong. I started the car again and it still ran like crap.

    A little bit of history: I recently replaced both O2 sensors on the car about a month ago and the car has been running a lot better; better acceleration and less fuel consumption. It was running rich and the O2 sensors were not functioning properly, hence, the replacement. The Cat converters are Magnaflows from 3 years ago with no more than 5K miles on them. I can probably safely assume that the Cats suffered the same fate as the O2 sensors due to the rich running condition. However, I have ran about 4 bottles of Catalytic Converter Cleaner prior to the O2 sensors replacement and each time, the car ran better until the O2 sensors fouled up again.

    After the O2 sensors replacement, everything has been fantastic and I actually got to enjoy the 3.91 LSD diff upgrade finally.

    The joy was short-lived as now the car runs like it's misfiring. Both exhaust runs hot so I don't think it's in Limp Home mode but there's no power (mixture is totally off). Instead of smelling rich exhaust, it now smells like a new car exhaust...rotten egg smell. That's very strange.

    What can the issue be? Are my Cats gone? Are the O2 sensors gone? I will wait until this weekend or so to troubleshoot but this is just strange.
    When my car was in LHM, it ran weak but motor was smooth. Now, it's just very lumpy and popping at the exhaust tip.

    Appreciate any help with diagnosing the problem.

    Chris
    Hey Chris, do you have a check engine light coming on? Could be alot of things.... May require a visit to bay area 8 series clinic where 8s get fixed and owners get buzzed))

  3. #3
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    Sounds giod, Ed. With the current condition, I will have to get it going again before I can drive up to your place to get it hooked up to the software.

    Sent from my SM-G955U using Tapatalk

  4. #4
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    No, CEL light is not on. But my brake assist light is. Brake assist light on wouldn't affect the way the motor runs though I'm sure.

    Sent from my SM-G955U using Tapatalk

  5. #5
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    Remind me did you already replace your FPRs? Could be that they are not holding pressure anymore...

  6. #6
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    Yes, with the ones I got the info from you, Ed.

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  7. #7
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    Strange, you think it's happening on both sides?

  8. #8
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    Just started up the car after about 4.5 hours of cool down. It seems the driver's exhaust side is running very rich. I can definitely smell the raw fuel at the exhaust on the driver side.
    I pulled the MAF connector on the passenger side (which feeds the driver's cylinder bank) and the engine runs smoother. I reconnected the passenger side MAF and disconnected the driver side MAF. The engine died immediately.

    This means the cylinder ID on cylinder #12 is bad...maybe? If the crank position sensor(s) (CPS)is bad, the motor will take many cranks to catch right? In my case, the motor starts up right away so I'm thinking it's not the CPS. I'm getting fuel as the car doesn't go through long cranks so the FPRs are at least working.

    I will have to pull the cap/distributors and check. I will also have to pull the motor oil catch and check on the 4 plugs there. How strange it just failed out of the blue and to me seems like some connection came loose. I certainly hope that's the case. I'm afraid my attempt at troubleshooting by having to run the motor will end up destroying the O2 sensors and Cats...

    Ed, and anyone...? Any thoughts to my rationale so far?

  9. #9
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    And you have or have not replaced the MAFs? Sounds like you have a bad one.


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  10. #10
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    I have never replaced a MAF. Geez, I hope not. I'll do the swap magic of the MAF to see if the problem follows. What's a good source of MAFs these days?

  11. #11
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    I would go FCP Euro or ECS tuning I bought some cheap ones off eBay for my 750 once and had all sorts of strange problems. Replaced with OEM quality MAFs and problems went away.


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  12. #12
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    At $1400 a piece...? That's a bit steep.

  13. #13
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    Quote Originally Posted by ChrisFuture8 View Post
    At $1400 a piece...? That's a bit steep.
    Check around. I bought 2 sets from Rockauto.com last year for around $145 each - they are still running fine.
    See if there is a Foreign Car Parts store near you - they may have some resources that you can't access. I know PYTHON remanufactured E31/E31 V12 MAFs several years ago, but they only sold directly to retailers, not to the general public.
    '93 850Ci - Mineralweiss Metallic
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  14. #14
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    Looks like they're out of stock. I searched both part numbers: 13621733678 (original part number that's now discontinued) and 13627527525 (re-manufactured MAF part number).

    Anyone else has purchased one of these MAFs from a third party source for the early M70 cars that had great success but didn't had to trade a liver for?

    Thanks.

  15. #15
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    Quote Originally Posted by ChrisFuture8 View Post
    At $1400 a piece...? That's a bit steep.
    Holy crap!! That’s some steep inflation since I️ bought mine a few years ago. Yikes.


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  16. #16
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    Before spending on MAF's - your problem sounds more electrical - HT, distributor cap and coil would be my first point of call.....
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  17. #17
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    What is going on?

    Timm is better at diagnosing than me, so certainly focus on his recommendations. My personal experience when I️ had the engine die when I️ tested by unplugging the MAFs it ended up being MAF failure.

    I️ did find a few other options for you if you determine MAFs are the issue:

    Walker brand (can’t vouch for quality, but jegs and Jc Whitney both carry) - http://www.jegs.com/i/Wildman-Produc...iABEgJSpfD_BwE

    Advance Auto parts carries their Cardone brand “remanufactured” for $160 and you can get 15% off that.

    Summit racing has the OEM Bosch for $430. Not cheap, but better than $1400 - https://www.summitracing.com/parts/b...CABEgLG9PD_BwE


    Sent from my iPad using Tapatalk
    MY SPEEDO ON THE 'BAHN!!! - @155!
    '07 e65|N62 - Alpina B7 - Black Sapphire|Black|Loaded
    '02 e46|M54 - Orient Blue|Beige|'Vert
    '00 e39|M52 - Anthrazit Metallic|Grey (Daughter's)
    '01 e38|M73 - Anthrazit Metallic|Schwarz|Shadow-Line
    '91 e31|M70 - Schwarz|Schwarz|M70

    '13 328i Auto - Black Sapphire|Coral Red|Sport Line|GONE
    '05 545i SMG - Jet Black|Black|Bamboo Anthracite|GONE
    '07 335i Auto - Montego Blue|Grey|GONE
    '05 545i SMG - (Euro Delivery 7/22/05)|Black Sapphire|Auburn|GONE
    '97 528i Auto - GONE

  18. #18
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    At Timm; true. I'm not ready to go and get a MAF yet, but I'm certainly putting that aspect down as a high possibility. I haven't time to work on the car other than pulling the MAF plugs for a quick test. I plan to take the motor cover off and a few other bits and start digging.

    This is the order of my troubleshooting:

    1: Check spark plug connections on bank 7-12
    2: Check 4 connections underneath oil catch tray
    3: Check connections at MAF and throttle body
    4: Check caps/distributors
    5: Check coil connections
    6: Swap MAFS
    7: Spray MAF on passenger side (supports driver's cylinder bank) with MAF cleaner
    8: Check connections of the sensors (3) by the firewall
    9: Pull spark plugs on driver's side and visually verify for damage
    10: Check O2 sensors at Cats

    The list may get longer if the culprit is not found

  19. #19
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    Right on. Thank you for the pointers!

    Quote Originally Posted by adwebinc View Post
    Timm is better at diagnosing than me, so certainly focus on his recommendations. My personal experience when I️ had the engine die when I️ tested by unplugging the MAFs it ended up being MAF failure.

    I️ did find a few other options for you if you determine MAFs are the issue:

    Walker brand (can’t vouch for quality, but jegs and Jc Whitney both carry) - http://www.jegs.com/i/Wildman-Produc...iABEgJSpfD_BwE

    Advance Auto parts carries their Cardone brand “remanufactured” for $160 and you can get 15% off that.

    Summit racing has the OEM Bosch for $430. Not cheap, but better than $1400 - https://www.summitracing.com/parts/b...CABEgLG9PD_BwE


    Sent from my iPad using Tapatalk

  20. #20
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    I had a similar sounding problem, although it was somewhat intermittent. Turned out to be a spark plug wire had broken (PO replaced with cheap aftermarket parts). Replaced plug wires with OEM and replaced plugs with the correct NGK and all good now.

  21. #21
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    Chris,

    Rotten egg smell is incomplete combustion in the engine. Do not drive the car. It is misfiring.
    Likely the cause is the a cylinder ID sensor failure or failing. Replace them both to be safe.
    Could also be a failed/failing Crank Position Sensor but my Spidey Sense tells me a bad Cylinder ID sensor in your case.
    Last edited by taylorpatterson; 11-14-2017 at 01:02 PM.
    Taylor in Cardiff

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  22. #22
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    Updates:

    :Checked spark plugs connection and made sure they are snug on driver side
    :Pulled crank position sensors (CPS) and cylinder ID sensors (CID) and sprayed with electronics cleaner and reinstalled
    Results: Started up the car and no improvements. Car now runs in full LHM and the "check engine" light is on. Only passenger bank running.

    :Pulled MAF supporting the driver side and cleaned with electronics cleaner and reinstalled.
    Results: No improvement and car still runs in LHM with CEL on. Only passenger bank running.

    :Swapped MAFs
    Results: No improvement and car still runs in LHM with CEL on. Only passenger bank running.

    :Pulled driver side CID sensor
    Results: Motor still fires up just fine and car still runs in LHM with CEL on. Only passenger bank running.

    :Reinstalled driver side CID sensor and pulled CPS sensor
    Results: Motor still fires up just fine and car still runs in LHM with CEL on. Only passenger bank running.
    :Plugged driver side CPS back in

    :Pulled passenger side CID sensor
    Results: Motor cranks about a second longer before firing up. Then, it dies. (of course the whole time, car is in LHM and CEL on with only passenger side running)

    :Reinstalled passenger side CID sensor and pulled CPS sensor
    Results: Car only cranks but does not fire up. (as expected)

    Assessment: The MAFs are fine.

    Now I need to chase after what's causing the driver side to go into LHM.
    I can hear the injectors firing on the driver side so it's a bit odd that it's in LHM. The exhaust is cold. I can even touch the exhaust manifold with my bare hand.

    Next will be the distributor/rotor assembly. Followed by checking for spark on the driver side spark plug cables.
    Will try to OHM out the driver side CID sensor
    Will check the O2 sensor on the driver side Cat
    Will check the DMEs

    Question, how do I check CEL without the special DIS/INPA software combo?

  23. #23
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    Hi Taylor. I hate to think that the CID sensor for the driver side bank is bad. About 3 years ago, I replaced the spark plugs wire set with brand new (around $450) set and has less than 5K miles on them.
    However, with that said, I have not ruled out the CID sensor either. But, keeping the thought in the back of my head that the set has very low miles so it will be thought of as a an item to replace at the lower end of the list.

  24. #24
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    Quote Originally Posted by ChrisFuture8 View Post
    Hi Taylor. I hate to think that the CID sensor for the driver side bank is bad. About 3 years ago, I replaced the spark plugs wire set with brand new (around $450) set and has less than 5K miles on them.
    However, with that said, I have not ruled out the CID sensor either. But, keeping the thought in the back of my head that the set has very low miles so it will be thought of as a an item to replace at the lower end of the list.
    Swapping them may not get you anywhere very quickly as the symptom could be from either bank but difficult to nail down to a single side.
    Can you swap both spark plug wire sets with a set from a known good running car just to test? At least then you'd know if they pass or if the cause is in those wires. I DO know that when a CID sensor goes bad, there are no lights, no errors logged making it a difficult issue to nail down root cause of.

    Also you said you were driving along fine on the freeway, then got off and drove surface streets for a bit, then stopped at a light before it failed. Heat is the standard enemy of these fricken sensors and so I'm thinking - highway heat - engine maintaining itis cool from air flow, then off the freeway, on surface streets and then stopped at a light, slight increase in engine bay heat - BAM the higher heat pushes an already failing sensor over the top. Assuming it does end up being a CID sensor of course :-)
    Last edited by taylorpatterson; 11-14-2017 at 01:50 PM.
    Taylor in Cardiff

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  25. #25
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    Quote Originally Posted by ChrisFuture8 View Post
    At $1400 a piece...? That's a bit steep.
    Don't rush and do that, A bad Maf would have thrown a CEL earlier during idle.

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