Diagnosing M62 smoothness problem

[n artis]

Hi, i have a 1996 535i manual with M62B35 non vanos engine. And i have been trying to solve a problem for some time.
662961Here is how my cylinder smoothness looks like.

662962And this is the screen from inpa about the adaptions.

Shouldn't the DME be doing some adaptions when some of the cylinders are not working correctly? Cyl5 is always the worst. Followed by coulpe of cylinder from the same bank. There are missfire codes almost every time i take the car for a drive, usually on bank 1.

Maybe some of you can give me a hint to what to look for, because i am pretty much out of ideas.
Have replaced spark plugs, moved coils and injectors around, replaced CCV, knock sensors, cam sensor, crank sensor, lambda sensors, replased used but working MAF sensor and ICV.

[H3adBussa]

Hi, i have a 1996 535i manual with M62B35 non vanos engine. And i have been trying to solve a problem for some time.
662961Here is how my cylinder smoothness looks like.

662962And this is the screen from inpa about the adaptions.

Shouldn't the DME be doing some adaptions when some of the cylinders are not working correctly? Cyl5 is always the worst. Followed by coulpe of cylinder from the same bank. There are missfire codes almost every time i take the car for a drive, usually on bank 1.

Maybe some of you can give me a hint to what to look for, because i am pretty much out of ideas.
Have replaced spark plugs, moved coils and injectors around, replaced CCV, knock sensors, cam sensor, crank sensor, lambda sensors, replased used but working MAF sensor and ICV.Run a compression check on each cylinder. If all psi readings aren't relatively close to each other, you could do the wet test also but I'd move straight to doing a leak down test on each cylinder. I believe that the compression #s should be within 7 psi of each other.

Do you have a Bentley manual for the car?

And yes, the DME should be adjusting adaptations for each bank.

Judging by the smoothness, cylinders 5,6 & 7 are having the issues. They are all on the same bank. I seriously recommend a compression then leak down test. Could be as bad as a bad head gasket on bank 2 but you won't know until you run the tests. Hopefully it rules that out and you can move back to more simple things.

Could always begin with a smoke test first to be sure there aren't any issues with the vacuum lines or gaskets sealing. Fix those issues if there are any, then do compression and leak down.

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[JimLev]

How's the smoothness when your at 1500 RPM?

[n artis]

I did a compression test some time ago. I do not have very detailed results (number of cranks to reach certain pressure etc) but all cylinders seemed ok, 14 bar or ~200psi. no major differences between cylinders. To be more precise, i could do it again.

I do have the Bentley manual.

As i saw no adaptions being made, i kind of ruled out fuel ralated problems, such as vacuum leaks. But i still replaced intake manifold gaskets, TB gasket, CCV gasket.
Yesterday I noticed that 2 of the intake manifold nuts can not be tightened on bank 2. Exactly the first 2 that are next to cyl5 and between cyl5 and cyl6. I guess the studs are stripped or something. Not fun. They are tight, but nowhere near as tight as the rest of them. I should deal with this problem, but i still don't get why there are no adaptions being made - if there is a vacuum leak here, it would make a lean mixture and DME should do something about it..

Unfortunately, there is noone in my area that does smoke tests. I did the simple thing - sprayed brake cleaner around possible leak spots. Nothing. Sprayed all around cyl5, no changes in engine behavior.

[n artis]

How's the smoothness when your at 1500 RPM?
1500 rpm is too high for smoothness to be registered. It is used for idle or very little throttle. The smoothness screen just freezes at last registered values when i get rpm that high.

[H3adBussa]

I did a compression test some time ago. I do not have very detailed results (number of cranks to reach certain pressure etc) but all cylinders seemed ok, 14 bar or ~200psi. no major differences between cylinders. To be more precise, i could do it again.

I do have the Bentley manual.

As i saw no adaptions being made, i kind of ruled out fuel ralated problems, such as vacuum leaks. But i still replaced intake manifold gaskets, TB gasket, CCV gasket.
Yesterday I noticed that 2 of the intake manifold nuts can not be tightened on bank 2. Exactly the first 2 that are next to cyl5 and between cyl5 and cyl6. I guess the studs are stripped or something. Not fun. They are tight, but nowhere near as tight as the rest of them. I should deal with this problem, but i still don't get why there are no adaptions being made - if there is a vacuum leak here, it would make a lean mixture and DME should do something about it..

Unfortunately, there is noone in my area that does smoke tests. I did the simple thing - sprayed brake cleaner around possible leak spots. Nothing. Sprayed all around cyl5, no changes in engine behavior.Hmmm. Sounds like you've been pretty thorough. Those compression numbers are solid. Quick question. You seem knowledgeable but I have to ask, you're running the smoothness test after the car has been running and was up to temperature right? Like after a good drive?

Maybe inpa just isn't reporting things correctly? Have you checked adaptations on a regular obd2 scanner?

With new plugs, coils, ccv, etc I'd expect your emissions related stuff to be fine but you'd still have some small number for the adaptations at least.

Do the precat o2 sensor voltage readings bounce from rich to lean repeatedly as they should? Do the rear o2 readings ever change or are they always .45?

I bought a smoke machine off Amazon relatively cheap. AutoLine Pro EVAP Vacuum Automotive Smoke Machine Leak Detector Diagnostic Tester Compact SMK-1 https://www.amazon.com/dp/B06XHRBKTM/ref=cm_sw_r_cp_apap_jwqPG2dh81EmY
Less than $100. Could probably make one for much cheaper.

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[n artis]

That smoothness screen is taken after car has warmed up and driven. But it is pretty much the same on cold start.
I guess i can try to read adaptions with something else, tried Rheingold but it does not want to read my DME for some reason.
Maybe after erasing adaptions(long time ago), the DME just wouldn't create new ones? Seems a bit extreme but at this point everything is a possibility i would like to consider.
This model has only pre cat sensors, there are no post cat sensors so the value always is shown as 0.45. Pre cat values change, but Inpa can not register these changes fast enough.

[alberttm]

Indeed strange. The only things remain are cables, DME or chain skip I guess. Cyl 5 no combustion at all, misfire, adaptations won't save anyway, though zero readings also seems to be not normal.

[n artis]

I have no magic suggestions beyond, fuel, spark, compression, and vacuum checks.
But, in reading that you have no post cat sensors, and that you have a European 96 model year, could this be running the obd1 style computer? (Like our 95 model year)
In that case no cylinder adaptation.

Yes, i have obd1 connector, the round one under the hood. You have a valid point here. Will look into it.

[H3adBussa]

Yes, i have obd1 connector, the round one under the hood. You have a valid point here. Will look into it.Seeing this is the case for your particular car, I don't have any experience with the earlier years so I can't offer anything additional. But I would definitely agree with Wagons ho and revisit the compression, leak down and vacuum recommendations from earlier. Seems you have a much simpler system to work with and things inside the engine may have changed drastically since the last compression tests you ran.

Sorry I can't help more, but I'll check in on the thread and see what shakes from it. Good luck!

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[n artis]

Ok, took the loose intake manifold nut off and found out that the stud next to cyl5 is stripped. Will try to replace that. Hope it is not a coincidence and this could fix my problem.

[n artis]

It has been a long time since i have worked on my car. But i finally managed to replace those stripped intake manifold studs. Torqued them to 15 Nm as Bentley manual says. "Surprisingly" nothing changed, but at least i crossed out one problem that might cause my problems.

I have a donor car, the same M62B35 engine, but auto (my car is manual). I am thinking about swaping the engine harness. What difficulties i would run into by doing this? Has anyone here done AUTO harness in MANUAL car?

Another question: i read in a post somewhere else that the knock sensors in theese engines need to be torqued to spec, otherwise they can make false readings. Also they can pick up noise from non-cylinder related parts like failing water pump bearing. I have replaced knock sensors, but i did not have a torque wrench at the time.
Is this something worth to re-do and torque to spec?

[TiesTorN]

I had a similar problem last year, I've tested & replaced every part you could think of but couldn't solve misfire issue (especially when the car was warm)

after a few months we found the wiring harness to be the cause. opened up the harness cover (which supplies power to coils) under the acoustic cover and saw that all the terminals on it were heavily corroded. we cut off all the terminals and welded the wires together which eliminated the corrosion problem and the misfiring problem solved...

[n artis]

I had a similar problem last year, I've tested & replaced every part you could think of but couldn't solve misfire issue (especially when the car was warm)

after a few months we found the wiring harness to be the cause. opened up the harness cover (which supplies power to coils) under the acoustic cover and saw that all the terminals on it were heavily corroded. we cut off all the terminals and welded the wires together which eliminated the corrosion problem and the misfiring problem solved...
I took time and re-did the coil pack wire connections under the black plastic covers on both banks. They were all corroded. I used WAGO terminals to connect the wires. Unfortunately it did not help.

Here is a picture of how those connections looked like:
665363

And theese are the terminals i used:
665364

[DnyCe220]

N artis, any updates? ever figure it out?

[n artis]

After giving up trying to fix this problem myself, i decided to take the car to a local BMW specialist. Unfortunately, my city was flooded after some heavy non-stop rain and i hydro-locked the engine. So never got to solve this issue.

I am replacing the engine in a week. If the missfires go away, my guess would be that the actual engine was the cause of them. If not, only wiring and DME is left to check.