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Discussion Starter #1
Hey Guys,

I got my m5 recently, and developed a misfire on cyl 3.

It only happens when cold.
It cuts out the fuel to cyl 3 to not send unburned fuel to the cat and damage it.

When Cold - engine is misfiring, you can feel it a little bit. When it warms up, it doesn't misfire anymore.

I get 002B37 fault code: Misfire with cut-out cyl 3.
I have replaced the spark plug with a new one, (i have ignition coil on order), the problem is still there, so I swapped ignition coils 3 and 4, the problem is still cyl 3. Yes only when cold - I actually let the car sit 5 hours, or the next day.

I also just got this code: 002796 Check at lower top.

So I got the compression guage out, and when i first fire it up, cyl 3 pulses up to 60 or 70 psi, then drops a little, but then pulses up to 130psi, and stays at that until I push the relief valve on the guage.

So i think the valves are being adjusted when cold and there is overlap which lets some pressure out? Any one have experience with this?

Anyway, I also swapped the ionic modules left to right. Which did not move the fault over.

I'm really starting to wonder if the wiring to the ignition coil is messed up ? I did have the ignition coil out and a spark plug in it pushed against ground and the spark was sparking, it didn't seem like a very strong spark but it was there...

Any help appreciated!
 

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Discussion Starter #3 (Edited)
How did the plug look when you removed it?
It was wet, smelled with fuel. However now with the new plug, and shortly after first starting the engine(still cold/ still misfiring) the plug is dry, so the ecu cut off the fuel to the cylinder.

I find when the engine warms up, it misfires less and less, and then it runs good without any misfires.
I checked with rheingold the quality of combustion, it's not the best but there are atleast 2 other cylinders which have same readings and no misfire, or codes on those cylinders... i'm hoping it is the fuel injector, I have some on order.
 

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Discussion Starter #4
Still waiting on my fuel injectors, and then finding time to replace #3...
But i fired her up today she was idling very rough, worse than usual, and i got these codes:
(CARLY)
Fault: Misfire with emissions deterioration cyl 3
Code: 2B44
Fault: Misfire with cut-out cyl 3
Code: 2B37
Fault: Motor emergency programm activated
Code: 2B57
Fault: Motor emergency programm activated
Code: 2796

After about 1 minute of this non sense I shut the engine off, and then started back up, and she was idling ok. I cleared codes and all seems well.

It's only happening for the first approx. minute when starting cold.
It's annoying me.

Anyone have any vanos valves Used but still ok that they want to sell?
I don't have any faults for vanos or vanos related components, but my values were not the best, I was thinking of trying to swap a different one in to see if this goes away. Not too happy about paying $350 for a stupid valve, x 4.
 

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Discussion Starter #7 (Edited)
Hey Jim... So I pulled the fuel rail out like in the clip, and had my wife push start twice, i felt the fuel rail get stiff (build up pressure) and No leaking from injectors.
I'm pondering if i should put the rail back in and just give the engine a quick turn , but not allow it to start or shut off just before it does, and then see if the injector stays on then?

The rail is tight, not much slack on the fuel line, so I can't really put see thru cups under the injectors to monitor the spray...
 

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Discussion Starter #8
Update;


I put 12v momentairly a bunch of times to the injector, it did release and close.

I swapped it with #4 until I get me new one.

Tomorrow I will fire her up and see what she says.

I'm more confused now, i was hoping it would be stuck open.
 

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Discussion Starter #9 (Edited)
Update;


I put 12v momentairly a bunch of times to the injector, it did release and close.

I swapped it with #4 until I get me new one.

Tomorrow I will fire her up and see what she says.

I'm more confused now, i was hoping it would be stuck open.
Update,

I hooked up my laptop w/Rheigold, and I cleared codes, and went to monitor the combustion quality.
When I first fired it up, Cylinder 3 was still dropping below 0.3 (red/fail) but not all the time, randomly. I also noticed cylinder 4 do it but only a very few amount of times. Cylider 3 eventually went to 0 red and just stayed there. At this point I decided to shut the engine off, and about 15sec later I fired it up again, still monitoring and now it never went below 0.3, and the engine did not run rough anymore.

Anyway, I'm wondering if its possible my wiring to the injector or to the coil is broken, or starting to break? Or do I have a bad coil and/or injector on both cyl 3 and 4 ?
I will post a screen shot soon.

I forgot to mention, the cluster stated 6 degres celcius; much warmer than the -2deg.C or colder that i've had to start the engine in over the last few weeks.
 

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You seemed to have checked many good things already. A thought: The secondary air injection is mounted on cylinder 3. When cold the, secondary air runs. Upon warm restart, I believe it may not. Could this be the difference? Disconnect you 2nd air hose from the injection check valve on that side and see what happens on cold start?
 

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Discussion Starter #12
So i tried to fire it up this morning when cold with rheingold monitoring spark quality, i fired it up, spark quality was decent - similar to other cylinders.

It was running rough as usual.

I then went to the combustion quality and cylinder 3 was always poor and finally it got shut off and stayed at 0, ofcoarse check engine light came up.


The secondary air thing - i'm not sure where on cyl 3 it is mounted? But when i ran the car last week to do the emissions monitors setting to ready, this is the one thing that would not set as ready.
I think you are right, it only operates for the first couple of minutes when engine is cold started, after that it doesn't any longer....

anyway, i'm still not sure where the hoses are and such... i will try to do some googling.
 

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Have you compare the compression number from other cylinders? Might be a vaccume leak somewhere. Did you see if the injecter actually pulses when first started? I had a 528 did the same thing before, I know it's not an M5, every cold start was running rough and check engine light on with #1 cyliner miss fire, and it would run fine if restarted. It turned out to be the oil separater had internal crack and cause a vaccume leak.
 

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Discussion Starter #14
yes i had around 130psi on cyl 3 and 4

i'm not sure about the oil seperator, or where it is on this engine...
 

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Discussion Starter #15
You seemed to have checked many good things already. A thought: The secondary air injection is mounted on cylinder 3. When cold the, secondary air runs. Upon warm restart, I believe it may not. Could this be the difference? Disconnect you 2nd air hose from the injection check valve on that side and see what happens on cold start?

I don't see how the secondary air injection is mounted on cyl 3?

could you specify which # to disconect?



 

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Oil separater is inside the intake mainifold and not changeable as it is part of the housing. Don't think secondary air injector has anything to do with the problem as it is only mounted on the outside on the cylinder3 general area. It doesn't go directly into the combustion chamber. You can try to disconect #8in the first picture to see if it helps. I would still check the gaskets around the throttle bodies, could be air leaks. And if possible, try to see if the injector actually fires when first started.
 

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Discussion Starter #17 (Edited)
Ok so another update, still misfiring..

So I warmed up the car drove around town, parked it outside its warm out today around 18deg celcius.
I washed it, went in and did house work, about 5 hours later I fired it up and kept gas pedal on to keep rpms at 2000 during the "cold start", kept it there for about 30sec, I could still feel the misfiring, but not as bad and no engine light.
I then let off the gas slowly, to a idle. Did not feel any misfire at idle now.
I put her in gear and went for a drive, 15km later with mixed driving I put in the obd scanner, and she has a cyl 3 misfire registered.

On monday I will put new ignition coil on, and I will have 2 brand new injectors, I may replace that also.
However I did already swap injector with cyl 4 and coil with cyl 4 and cyl 2.
I still have this cold start misfire only on cyl 3.
 

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Are the flaps in your throttle actuators moving in unison? The throttle body gasket check is another good one. I thought about suggesting this but you said it was a startup-only issue. And it is the idle actuator that controls this; not the throttle actuators. Move the throttle blades by hand; check for stiction and excessive resistance.
 

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Discussion Starter #19
Are the flaps in your throttle actuators moving in unison? The throttle body gasket check is another good one. I thought about suggesting this but you said it was a startup-only issue. And it is the idle actuator that controls this; not the throttle actuators. Move the throttle blades by hand; check for stiction and excessive resistance.

Yes its only on cold starts, and if I let it run for 30sec then shut off and restart it idles fine and no misfires.

The flaps in the throttle bodies? Yes these all move together in uniason. The throttle actuator did seem like it was tought to push on, but I took the little plunger off the throttle bodies and they moved freely.
I have not focused on throttle body gasket at all when I had the intake manifold off, maybe i should have looked for deterioration, but the individual throttle body boots comming off Intake manifold looked good and solid. I did put a small coat of oil on to help it come off next time, because it was on there really good.

I dont have ang codes for throttle bodies. I did have once on a colder morning a idle control valve code, where the engine idled rough but shortly after that went away and I havent had it happen for over 4 weeks now.
 

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Discussion Starter #20
Just a quick question, just to double check... cylinder 3, which one is it? I better not have the wrong one... I did google it and as far as I know it is the 3rd from the front of car on the passenger (right) side of car. Correct?
 
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