M60B40 sudden onset idle vibration

[Layne]

Started the car one evening, and it vibrates so bad I shut it down and immediately went looking for the cause. No belt or fan had flown off, so I thought it was the OSV again. Swapped to a spare with no change. Saw the fan belt flopping around a bit, but running without it also produces no change. I think the belt is flopping as an effect, not a cause. Took it for a highway cruise just now and it runs totally normal. Acceleration is on point and fuel economy is normal. Can't tell anything is wrong until it falls back to idle. Idle is at the perfectly normal speed just above 500rpm. Revving up to 1000 or so nearly eliminates the vibration. Anything above that and it's gone. Engine mounts are good, the engine doesn't shake within the car, it shakes the whole car. Clutching in or slipping the clutch a little in gear causes no change, so I don't think it's flywheel related. I tried listening to the fuel injectors with a stethoscope, but they don't make any sound (weird?). Acceleration should suffer anyway if that's the issue. Disconnecting the MAF produces no change. Disconnecting the ICV just causes it to speed up. It's a euro car, so it doesn't have a check engine light. Might need to retrofit one for diagnostics.

Thoughtful, intelligent responses appreciated.

[Sir Montalbon]

Disconnecting the MAF produces no change.

This is the only thing that jumped out at me. Is it possible that the MAF is malfunctioning at the lower edge reading, and reporting to the DME more accurately when it sees more airflow? Maybe look for a change by disconnecting the MAF while simultaneously applying some throttle. If still no change, I'd try a spare MAF if you have one sitting around.

[Layne]

I'd try a spare MAF if you have one sitting around.

I do, it's worth a shot.

I thought it was supposed to idle normally without the MAF, but then runs badly at higher revs. I've heard of the MAF causing idle problems that go away when it's disconnected.

[Sir Montalbon]

You may be right. I haven't had too many MAF issues in my years with e34's, so I'm not polished on their finer points. I've just always understood that if you disconnect the MAF and it runs worse, then suspect the MAF. Curious to see the results.

[NikosX]

Sounds like a misfire. I'll bet you have one or multiple weak coils.


Sent from my iPhone using Tapatalk

[Layne]

I used a test light to probe the CEL pin on the engine harness, and it works (euro car remember, there's no wiring for it on the chassis side). Got code 1213, which is lambda bank 2 and could basically be anything. No use there. Spark plugs were very worn (almost 4 years old) so I changed them out, no change. I swapped the coils on bank 2 with some of my spares, no change. I'll try swapping the other coils tomorrow, but I've never actually had one go bad. Swapped the MAF for my spare, also no change.

[moroza]

Harmonic balancer runout is on my mind, because I noticed a fair bit on mine yesterday (with 262k). Does the fan belt still flop around at 1000rpm?

I hit a deer some months ago, putting a giant hole in my MAF. I didn't know this until the next day after limping home at about 1100rpm (fan was jammed against the radiator and spinning on its clutch, so I kept the revs down). Car idled great and made the drive at ~35mph with no CEL or other indications of engine problems.

Can you tell if it's actually running poorly, or just shaking?

[mboor]

When i disconnect the maf on my M60, it stumbles just a bit and settles into a high idle. Its runs ok, but not quit as smooth as when its plugged in (obviously). You should notice some kind of change in engine rpm when you disconnect the maf.

- - - Updated - - -

fwiw, when my maf failed a few years ago, it ran perfect until i hit the highway, Then it left me stranded on the side of the road. i unplugged it and it ran normal until it was replaced.


by chance are you getting a "check oil level" or "oil level sensor" message on your cluster display?

[Layne]

When i disconnect the maf on my M60, it stumbles just a bit and settles into a high idle. Its runs ok, but not quit as smooth as when its plugged in (obviously). You should notice some kind of change in engine rpm when you disconnect the maf.

by chance are you getting a "check oil level" or "oil level sensor" message on your cluster display?


I disconnected the MAF with the engine off and restarted. So probably 'some kind' of change, but it didn't alter the vibration. MAF is only a few years old.

No oil level alerts.

- - - Updated - - -


Harmonic balancer runout is on my mind, because I noticed a fair bit on mine yesterday (with 262k). Does the fan belt still flop around at 1000rpm?


Can you tell if it's actually running poorly, or just shaking?

The crank pulley is running perfectly straight. I tried to flex the harmonic balancer rubber with the belt off and could not find any movement. Nothing visible there when running.

The belt is flopping on the far left side above the power steering pump. Maybe the belt has stretched or the tensioner spring needs to be replaced. Definitely not related to the problem though.

Seems to actually run poorly, ie; it would be easy to stall when taking off if you didn't get over the RPM where it goes away.

[NikosX]

CPS.


Sent from my iPhone using Tapatalk

[ross1]

Is this a vibration only or shaking due to misfire?

[Layne]

CPS.

Also only a few years old. But easy enough to try the spare. The only motronic parts that I haven't replaced are the cam sensor and the coils.


Is this a vibration only or shaking due to misfire?

Are they not the same thing? It shakes bad. Bad enough to not drive until it's fixed.

- - - Updated - - -

I had a thought... since I just bought new spark plugs and haven't driven on them yet, I could idle for 5 minutes and see if one stays cleaner than the rest...?

[ross1]

"Are they not the same thing? It shakes bad. Bad enough to not drive until it's fixed."
No, plenty of ways for an engine to shake or vibrate without having a misfire.
Given your response I'll assume it is misfiring, so either spark or fueling. I think CPS to be very unlikely as it would ostensibly work or not at all but as you say easy enough to swap and at least eliminates the question.
Can you isolate the effected cylinder(s)? Disable coils or injectors and observe.

"I had a thought... since I just bought new spark plugs and haven't driven on them yet, I could idle for 5 minutes and see if one stays cleaner than the rest...?"
Or wet plugs from no spark

[moroza]

"Are they not the same thing? It shakes bad. Bad enough to not drive until it's fixed."
No, plenty of ways for an engine to shake or vibrate without having a misfire.

That's kinda what I was getting at. Bad motor mounts or an imbalance in the rotating assembly (harmonic balancer, flywheel) would make even a perfectly-firing engine shake. A misfiring engine will shake even with perfect mounts/balance.

Check the plugs, of course, but if it runs fine above 1k rpm then I doubt that's it. Less effort would be to check the CPS; you're looking for 490-540 ohm IIRC (don't recall which pins), and they are known to go bad over time.

[ross1]

Any progress?

[Layne]

Any progress?

No. Rained all weekend. Now back to work.

[Layne]

I discovered that disconnecting all 4 coils on the left side at the same time makes very little to no difference in the idle (although it does slow down the engine's ability to rev up). Disconnecting any one coil on the right side makes it much rougher/almost dies.

I tracked down all connections specific to the coils and injectors on the left side (they're all in the left side wiring box) and found some light corrosion, but no faulty connections.

If there were mechanical damage to the left side (cam jumped time etc) I don't see how it would rev up normally and have good power.

I tried a different DME with no effect, swapped coils around, cleaned the coil ground strap, etc.

[moroza]

Well, sounds like it's a problem on the left bank. That narrows things down considerably. Even if they test/look ok, I'd run new grounds (if temporarily) for the left coils and/or injectors, see what happens. Perhaps you have cracked wiring in places? Heat and age will do that...

[acepilot]

I am going thru this exact problem right now with my 540. Sudden vibration, seems like a misfire, esp at idle. Got the same check engine light 1213. Going thru all the treads with the 1213 code. Replaced the fuel filter, valve cover gasket (oil in the spark plug), 02 sensor, and PCV plate. The MAF seems to be ok, ohmed it out and seems to go up and down with it's output voltage. One person on the web reported replacing the fuel regulator on the fuel rail. So will check the fuel pressure and see if that's the problem. Checking for vacuum leaks is going to be difficult unless I do a smoke test, which I haven't made any piece of equipment to do that. At 181k, I didn't do the intake seals yet, so that maybe another thing to worry about. Interestingly, I have the carsoft program, and looking at the live data, the MAF is not changing when I throttle the car. Also the intake temp sensor reading is also wrong. So may have to look into that.

Otherwise, I'm stuck in the same boat. Looking forward to seeing what you find in your car.

Ace

[ross1]

12v at the red wires for the injectors? 12v at the green for the coils? It would be very remarkable for all four coil or injector drivers for one bank to die at once, so DME, probably not.
It's starting to sound like valve timing on that bank. Comparing compression between banks ought to give a clue. The sudden onset would be consistent with that.
At idle more time for pressure to bleed off through a valve hanging open, as revs increase this effect is less noticeable.
Good luck, hope I'm wrong.

[Layne]

Yes power is good at the green and red connections. A compression test is probably the next step. Aside from cam timing, or some strange wiring harness problem, I'm out of ideas.

[mrgraybeard]

You might check exhaust back pressure for the affected bank. A blocked cat (or other exhaust blockage) can produce vibration in the V8s. Elevated crankcase pressure/blowby is another symptom.

[acepilot]

Any progress??

[Layne]

I tested compression on cylinders 1, 5, and 8. All were over 210psi. (Surprisingly high actually) I might as well go back and do all 8 when I have time and a fully charged battery, but it looks like there is no mechanical problem on the left bank.

Possible clue: the new spark plugs were black with soot on the left side after only a few minutes of idling. The right also had more soot than I would expect, but the left was fully black.

[Layne]

You might check exhaust back pressure for the affected bank. A blocked cat (or other exhaust blockage) can produce vibration in the V8s. Elevated crankcase pressure/blowby is another symptom.

A good idea to check, but I can't see how higher rpm power would not suffer in that case.

[ross1]

I tested compression on cylinders 1, 5, and 8. All were over 210psi. (Surprisingly high actually) I might as well go back and do all 8 when I have time and a fully charged battery, but it looks like there is no mechanical problem on the left bank.

Possible clue: the new spark plugs were black with soot on the left side after only a few minutes of idling. The right also had more soot than I would expect, but the left was fully black.
Reading plugs after only idling and especially after a cold start aren't going to tell you much so the soot isn't too surprising BUT the difference one bank to the other certainly is.
So, left bank is over rich, strong fumes and sooty plugs. Are the coils grounded well on that side?

[bmwdirtracer]

Hi, Layne,
I usually hang out in the Mechanical forum, but one of your friends who's been trying to help here asked me to have a look, to maybe lend an additional perspective. My 2 cents:

Two things stood out, on first reading:
(1) ~500 rpm idle speed seems excessively low to me. The lowest idle speed I recall, on any BMW, is somewhere between 650 and 680.

but, then, I saw the BIG #2:

You can disconnect ALL 4 coils on bank 2, at the SAME TIME, and perceive no change ???? Oh, DAMN.!

If I found this information to be true, when I was examining such a car, the first thing I would do is recheck my testing...I would suspect that I'd made an error, if the car runs normally above idle.

If I disconnected all 4 coils again without making a difference, at idle, and the car still runs perfectly above those revs, I have to think that there's an electrical fault at a coil or injector gang junction, for that bank.

http://wedophones.com/Manuals/BMW/1995%20BMW%20525i%20-%20525it%20-%20530i%20-%20530it%20-%20540i%20Electrical%20Troubleshooting%20Manual.pd f

Page 105 of the Adobe document, BMW page 1210.11-01.

The only feeds I show which pertain to all 4 cylinders on bank 2 involve either the coil grounds at that bank, or this fuel injector circuit.

On this injector circuit shown, there's the X6820 splice, where the 2.5mm red/white turns to the .75 wires going to each cylinder of that bank. That splice may be damaged, I'd check voltage drop across that splice.

But, well, you've got an O2 sensor code for the same bank. Certainly, O2 sensor codes are grossly common on the older cars, and could be set by just coasting down a hill.

However, you have BOTH a code for something specifically relating to that bank, plus an apparent bank-wide misfire at idle. That sensor and wiring must therefore be suspect. (page 109). Given the code and symptoms, I think I'd throw an O2 sensor at it, myself.....it was a maintenance replacement item about 12 years ago.

Does this misfire/dead half an engine only occur below, say 750 rpm? If so, test battery voltage at those ultra-low 500 rpm idle speeds.

Lastly, a good BMW diag program can show you smooth-running values and other data, even for these old cars. My last workplace, on Maui, had an old Snap-On "BRICK" that could show you a tremendous amount of data, even on a '91 535..

Just food for thought. All the best,
Chris


Oh, a last thought: I'd highly recommend unbolting and cleaning the engine main ground wire, at both ends, then rebolting.. I can't remember if it pertains to the E34 V8 cars, but on E38s and E39's, if you leave the engine main ground loose, the stainless shielded oil filter housing pipes become the ground very often, and play hell with the electrical system, until they melt the rubber or create so much smoke that someone catches it.....

[acepilot]

Still thinks it's fuel air mixture problem as oppose to any actual mechanical problem. When I cleared my DME code, the car actually ran pretty good with strong pulls until the check engine light came on. Now, my CEL is reading a 1221 passenger side O2 sensor, which I think is a false reading. So something is amiss with the air fuel ratio causing a misfire. Therefore the rough idle.

By accident, I left all the fuel injectors disconnected on the drivers side after I redid the valve covers and the idle was rough abit more but certainly can be similar to the rough idle I am experiencing. So I can see how disconnecting one bank can seem to have not much of an effect.

Then again my problem more than likely will be different than yours.

Ace

[Layne]

Hi, Layne,
I usually hang out in the Mechanical forum, but one of your friends who's been trying to help here asked me to have a look, to maybe lend an additional perspective. My 2 cents:

Thanks for coming in, I appreciate the input.



Two things stood out, on first reading:
(1) ~500 rpm idle speed seems excessively low to me. The lowest idle speed I recall, on any BMW, is somewhere between 650 and 680.

Well I said just above 500. That probably means 650. Either way, it's the same as it always was.



but, then, I saw the BIG #2:

You can disconnect ALL 4 coils on bank 2, at the SAME TIME, and perceive no change ???? Oh, DAMN.!

If I found this information to be true, when I was examining such a car, the first thing I would do is recheck my testing...I would suspect that I'd made an error, if the car runs normally above idle.

If I disconnected all 4 coils again without making a difference, at idle, and the car still runs perfectly above those revs, I have to think that there's an electrical fault at a coil or injector gang junction, for that bank.

That's correct. When the engine was idling at it's worst, disconnecting all 4 made almost no difference. When it was idling a little better (it's sort of randomly changing all the time), each one made a very small change, not on par with disconnecting any one on the opposite side. With all 4 disconnected, the engine still revs up somewhat smoothly, but much more slowly. They are clearly coming back on line at some speed around 750-1000 rpm.



http://wedophones.com/Manuals/BMW/1995%20BMW%20525i%20-%20525it%20-%20530i%20-%20530it%20-%20540i%20Electrical%20Troubleshooting%20Manual.pd f

Page 105 of the Adobe document, BMW page 1210.11-01.

The only feeds I show which pertain to all 4 cylinders on bank 2 involve either the coil grounds at that bank, or this fuel injector circuit.

On this injector circuit shown, there's the X6820 splice, where the 2.5mm red/white turns to the .75 wires going to each cylinder of that bank. That splice may be damaged, I'd check voltage drop across that splice.

I checked that one and it's good. I scraped the slight corrosion away and wrapped a piece of wire around so it contacted all the wires with no change at all. Also did the same with the X6453 coil ground, and X6829 coil power. I found 13+ volts at both power splices.




But, well, you've got an O2 sensor code for the same bank. Certainly, O2 sensor codes are grossly common on the older cars, and could be set by just coasting down a hill.

However, you have BOTH a code for something specifically relating to that bank, plus an apparent bank-wide misfire at idle. That sensor and wiring must therefore be suspect. (page 109). Given the code and symptoms, I think I'd throw an O2 sensor at it, myself.....it was a maintenance replacement item about 12 years ago.

I agree they're probably due for replacement anyway, but the problem occurs even at a cold start when there is no O2 feedback.



Does this misfire/dead half an engine only occur below, say 750 rpm? If so, test battery voltage at those ultra-low 500 rpm idle speeds.

Yes that's about right. Voltage is good though (high 13's to low 14's at idle, with a low-ish battery). Had the alternator rebuilt a few years ago. I have seen what you're talking about though, voltage drops to just battery voltage at idle.




Lastly, a good BMW diag program can show you smooth-running values and other data, even for these old cars. My last workplace, on Maui, had an old Snap-On "BRICK" that could show you a tremendous amount of data, even on a '91 535..

Never had any experience with that. Probably something I need to learn. I don't own a laptop unfortunately.




Oh, a last thought: I'd highly recommend unbolting and cleaning the engine main ground wire, at both ends, then rebolting.. I can't remember if it pertains to the E34 V8 cars, but on E38s and E39's, if you leave the engine main ground loose, the stainless shielded oil filter housing pipes become the ground very often, and play hell with the electrical system, until they melt the rubber or create so much smoke that someone catches it.....

I recently replaced it. The car wouldn't start when it failed. Easy enough to check again.

[Strife]

Sure coils or boots aren't suspect? The boots take a beating over the years if the car hasn't had them changed due to periods of misfiring from the typical oil/water collection in the wells.

[Layne]

Sure coils or boots aren't suspect? The boots take a beating over the years if the car hasn't had them changed due to periods of misfiring from the typical oil/water collection in the wells.

Yes I'm sure. I have many spares and have swapped them in every possible combination.


My latest idea was that the coils weren't grounding through the little strap to the head (assuming they need to. It's not readily apparent if the high tension side grounds here, or through the ground wire in the connector). Connecting an extra ground to the valve cover does nothing though.

I compression tested cylinders 6 and 7 in case the headgasket was blown between them (I only checked 5 and 8 last time on the left side), but nothing there, compression is good.

Repeating the coil disconnect test, I got the same results as last time. Disconnecting cylinder #5 (front left side) makes a *slight* difference in the running, but cylinders 6-7-8 make NO difference. I don't know what this slight difference between #5 and the others could point to. This result is the same regardless of the order they're disconnected in, or how many are disconnected at one time.

The plugs on the dead cylinders appear to be sparking (they have clean spots where the sparks should occur), but the next test is probably to visually verify the spark somehow. (not easy with the coil leads being so short). Maybe next would be to swap the fuel injectors side to side? Probably pointless, there's virtually no way multiple fuel injectors could fail simultaneously.

[Layne]

After not using the car for a while, I decided my only chance of locating the problem is to try to break it worse. So I've been driving it again. And it is getting worse. A couple times today after a warm restart (2-3 hours resting), the problem did not go away at 1k rpm as per usual, but persisted at any rpm. This leaves the engine running very rough with very little power, but then right as the temp gauge almost touches the middle mark (after about 2 minutes), the power is back on like a light switch. Not including below 1k rpm, that part is exactly like it was.

I don't know if that's a useful clue or not....

[flying525]

After not using the car for a while, I decided my only chance of locating the problem is to try to break it worse. So I've been driving it again. And it is getting worse. A couple times today after a warm restart (2-3 hours resting), the problem did not go away at 1k rpm as per usual, but persisted at any rpm. This leaves the engine running very rough with very little power, but then right as the temp gauge almost touches the middle mark (after about 2 minutes), the power is back on like a light switch. Not including below 1k rpm, that part is exactly like it was. I don't know if that's a useful clue or not....

I haven't read through this whole thread so sorry if what I'm going to say here is old news. The underlined bit above are the classic symptoms of a crack in the cylinder head that seals up when the engine is hot enough. When the engine is cold, the crack remains big enough to cause rough running. As the engine heats up, the rough running begins to subside. But at a certain temperature, it stops entirely. The metal expands into the crack in such a way as to seal it.

There are a couple of ways to check this, non of which are easy or cheap or quick. First, do a compression test on all banks when hot, then let the engine cool down to cold, then do another compression test. The chambers with the crack will show lower compression numbers than when hot. The second way is to use a block tester. Open the rad cap and run the engine till hot. Then use the block tester. It should be ok. Then let the engine cool down totally. Start it and test again with the same fluid (since it shouldn't have changed color earlier because there's no crack when the head is hot).

The third test is more of a ruling out. Check everything that could cause rough running. Vacuum leaks, smoke test, carburetor cleaner test, all sensors, plugs and coils. If everything is ok, what is left - cylinder head - must be the answer.

Anyway, for M60 engines, there is a common issue. Intake gaskets shrink too much when cold. Vacuum leaks are created. The engine runs rough. Then as the engine heats up, the metal expands to seal into the shrunken gaskets, sealing the vacuum leak. This is easily tested. Just spray carb cleaner at the intake gaskets when running the engine when cold. Mentioning this last because it would probably have been mentioned first in this thread.

[Layne]

I appreciate the input, especially since no one else has any. But a crack does not open and close 'like a light switch'. And there would be no explanation for the problem appearing below 1000 rpm at all temperatures and disappearing above 1000 rpm. The problem is quite clearly electrical in nature.

I drove the car 7 hours this weekend with no problems at all. Gas mileage is about the same as ever. The problem only occurs at idle, although if you let the revs drop too low in gear it starts bucking a little.

[corcovado]

I had the same exact problem on a different car, a 4 cylinder Honda. Bucking and rough running at idle, but as soon as you rev it, smooth as butter. Turned out to be the CPS sensor. Did you already try replacing that? I'd replace both cam/crank.

[Layne]

I had the same exact problem on a different car, a 4 cylinder Honda. Bucking and rough running at idle, but as soon as you rev it, smooth as butter. Turned out to be the CPS sensor. Did you already try replacing that? I'd replace both cam/crank.

The crank sensor is only a few years old (genuine BMW) and has the correct resistance (not really a definitive test, I know). I have spares I can try anyway. The cam sensor has not been replaced, but also has the correct resistance (not the same as the crank sensor, btw). The car runs exactly the same with or without the cam sensor connected. Unfortunately I don't have a spare one to test with, but finding one is probably a good idea.

[flying525]

I appreciate the input, especially since no one else has any.

Thank you. And you've had alot of responses already.


But a crack does not open and close 'like a light switch'.

Oh, some cracks certainly do.


And there would be no explanation for the problem appearing below 1000 rpm at all temperatures and disappearing above 1000 rpm.

I see. Didn't read that. Didn't read the whole thread as I mentioned in my first post here. Yes, that does not sound like a crack at all if this behavior is temperature independent.


The problem is quite clearly electrical in nature.

Possibly.


I drove the car 7 hours this weekend with no problems at all. Gas mileage is about the same as ever. The problem only occurs at idle, although if you let the revs drop too low in gear it starts bucking a little.

If i'm free I will read your thread on the flight back next weekend and maybe I'll spot something that hasn't been tried. Fresh eyes.

Short answer for electrical engine problems is, error codes, and the disconnect test, bearing in mind that you may have two sensors damaged at the same time which complicates troubleshooting. Short answer for rough running is usually a vacuum leak, detectable with a smoke test.

[eddycooper]

Given the temperature dependence, the coolant temp sensor is something that's fairly easy to check. I'm not sure it would explain all the symptoms though.

[ross1]

coolant temp sensor will not cause a condition that will discriminate among certain cylinders.
Layne,
Have you considered a goofy crank pos sensor? Also I seem to recall hearing about M60s with wonky crank hubs that cause odd misfires, perhaps food for thought.

[Layne]

I tried a spare CPS, the outcome was odd. It was instantly about 80% better, although not totally smooth at idle. But over the course of the day and multiple restarts, it went right back to the way it was. Weird coincidence, or something to do with the CPS? I don't know.

I've seen the bad harmonic balancer before on an M5. Definitely a possibility, but I can't move it at all by hand and can't see it wobbling at all while running. The rubber that I can see looks totally fine. Should probably hit it with a prybar and see if I can find any movement that way.

[MauiM3Mania]

Was your issue resolved?

[shogun]

I see. Didn't read that. Didn't read the whole thread...

If i'm free I will read your thread.....

If you do not have time to read a whole thread, do not answer, before you had time to read a thread.
This is not the first time that you comment in threads without reading the whole thread and that is only confusing forum members.

[flying525]

Hi Shogun,


I see. Didn't read that. Didn't read the whole thread...If i'm free I will read your thread.....


If you do not have time to read a whole thread, do not answer, before you had time to read a thread.This is not the first time that you comment in threads without reading the whole thread and that is only confusing forum members.

Your quote was not fair. You selectively quoted that from the second post I made in this thread. That's CNN fake news tactics. Here's a quote from the first post I made in this thread, and in fact from the first line of the first post :


I haven't read through this whole thread so sorry if what I'm going to say here is old news. The underlined bit above are the classic symptoms of a crack in the cylinder head that seals up when the engine is hot enough.

So when I've signposted the fact that i haven't read the whole thread yet, I've stuck to acceptable rules of talking. People factor that in and are not confused. And the OP appreciates the comments on an thread that had stalled for 6 weeks:


I appreciate the input, especially since no one else has any.

[Layne]

Was your issue resolved?

No. In fact I tried to drive the car this morning and had to tow it back. The problem has progressed to basically not running at all, although it still had normal power momentarily at times. My top suspect at the moment is the cam sensor. It's the only part I don't have a spare of to test. I disconnected it earlier while the engine was running and observed no difference. I assumed that once the engine had started, the computer 'knows' which cycle it's on and no longer needs the cam sensor. I now believe that's incorrect, and the computer likely 'asks' the cam sensor whether it's on an exhaust or compression stroke with EVERY rotation of the engine. I disconnected it today before starting the engine and it started and ran exactly the same (terrible), then stopped the engine and reconnected it before proceeding on the drive where the car could no longer go after 1/2 a mile. The engine I think is supposed run in wasted spark mode if the cam sensor is completely disconnected from start up, which means it should have run better without it if it's faulty, but it did not. So I may be wrong. But it's something to try, and the only fuel injection part left on the car that's over 20 years old.

[MauiM3Mania]

I'm going to copy this thread to the General Mechanical sub-forum in hopes that one of the techs there can help. It's late in the day, so hold tight.

I will ask that members that are guessing or don't take the time to read the thread before offering their ideas to please refrain.

EDIT: Parallel discussion here. https://www.bimmerforums.com/forum/showthread.php?2347478-M60B40-sudden-onset-idle-vibration

[flying525]

Ok so I read through this thread.


Repeating the coil disconnect test, I got the same results as last time. Disconnecting cylinder #5 (front left side) makes a *slight* difference in the running, but cylinders 6-7-8 make NO difference. I don't know what this slight difference between #5 and the others could point to. This result is the same regardless of the order they're disconnected in, or how many are disconnected at one time.

Its pretty clear to me that unless you figure out exactly why unplugging 6,7,8 makes no differences to the engine, you're not going to get anywhere. Is it supposed to be that way ? An M60 thing ? Someone could help the op test this?

And op could you rig something up and do a smoke test M60 intake gaskets are known to be crap at this age. YT has some vids on this. My home brew cost me a few bucks to get done and its good.

Your cam sensor has nothing to do with this. Cam sensor is for precise fuel timing. Without it your fuel economy will suffer slightly. But you won't get idling, misfire, and other problems.

You remind me of a guy I'm helping offline. He had a long thread which everyone gave up on after awhile. So EVEN after all the work that he had already done, I got him to repeat everything and we found the following problems :

a. Vacuum leaks x 2. Fixed.
b. Injector no5 spray pattern not right. Fixed with a spare injector.
c. Bad dme. Fixed by buying a spare.
d. Problematic icv. Fixed by buying a good spare.
e. Poor diagnostic and observational skills. I'd say he's about halfway to fixing that.

All of the above has lead to a drastic improvement in his car. It has eliminated around 80% of the symptoms. The last two persistent systems we are working on right now.

Point is that you could have many problems on the engine going on at the same time. You need to fix or rule out each clearly identified one, one by one. There is no other way. If your symptoms were straightforward for the M60 someone would have given you the right answer by now. You probably have several issues all contributing to this so you need to check, rule out or fix each one you spot, and then go onto the next, until they are all done.

Now your engine does not run at all, you need to treat it as a standard no start first. Check your cps resistance, fuel pump relay, fuel pump, confirm you have spark during crank. Then check if your fuel regulator is leaking. Unplug your coolent temp sensor. Then try to start the engine.

And I read your thread. No, 500 rpm is not the same as 600 rpm and is not the same as 650rpm. Unless there is something wrong with your tach, you should be able to tell exactly where your idle rpm is. Like the tech who replied to you here earlier said, adjust your throttle cable screw at the throttle until you get 650 rpm and not a smidgen less. You can set it to 700rpm if its easier, for the time being.

Good luck.

[ross1]

Oh yeah, it's him again.

[MauiM3Mania]

Not much doubt.

[Sir Montalbon]

Oh yeah, it's him again.

Lol

[ross1]

I can't believe that he managed to stifle himself for so long, must have been painful.
Sorry Layne