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2006 M5 Alpine White
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You fixed yours correct? what was it?
Mine was fixed by gutting the primary cats and getting a tune, so I can only assume the misfires were due to clogged primaries.

It'll misfire and idle really rough until it's basically warm. So 8-10mins? restart car after that and all is good. Idles smooth, no more misfires, runs good
This is WAY longer than any of my symptoms persisted so I don't think we're comparing apples to apples anymore. @platii mentioned your compression seems low compared to spec.
What do your other cylinders measure?
Was that measurement taken cold?
Could you measure it warm and compare?
 

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Discussion Starter · #22 ·
Yeah measurement was cold. And the pic is misleading taken at an angle it was actually at 82+
All other cylinders were identical.

I have not done the test when fully warm. Good call.

Mine was fixed by gutting the primary cats and getting a tune, so I can only assume the misfires were due to clogged primaries.



This is WAY longer than any of my symptoms persisted so I don't think we're comparing apples to apples anymore. @platii mentioned your compression seems low compared to spec.
What do your other cylinders measure?
Was that measurement taken cold?
Could you measure it warm and compare?
 

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I'm not sure if you mentioned but since you have inpa are the cams meeting targets when cold? There is a cold start profile, I don't the maps in front of me to tell you more but I had similar issue on the E39 on middle RPM engine braking, only one cylinder misfiring and leading to cut out , more fuel worked around it but it turns out the vanos wasn't meeting targets. I ended fixing the solenoid reverted the fuel maps and everything is working as expected again. I wouldn't believe it if I didn't see it.

Might be worth the quick test to see expected vs actual cam timings when cold.
 

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Correction:
The minimum compression is 6.5 bar= 94.28 psi.

The TIS doesn't mention to warm up the engine.
Generally performing cold compression test gives more accurate reading if you are in diagnosing mode. Activate the starter for 8 seconds to test for compression.

In this example the cylinder compression value was low but the question to compare it with other cylinders is to rule out valve train or bottom end leakage issue, (reduced individual cylinder quality).
Note, good compression test will not rule out broken spring/lifter.
 

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2006 M5 Alpine White
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Correction:
The minimum compression is 6.5 bar= 94.28 psi.

The TIS doesn't mention to warm up the engine.
Generally performing cold compression test gives more accurate reading if you are in diagnosing mode. Activate the starter for 8 seconds to test for compression.
Agreed. However my thought process was that it appeared low when cold and ran rough cold but ran fine after warm. So comparing cold and warm could tell us something. It sounds like all the cylinders are testing similarly, however, so probably not the case.
 

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I have no SAP codes. The fuel injector in cyl 5 was never leaky and I only replaced it due to this issue.
I see vapors coming from exhaust on start-up just fine. Assuming SAP works. I swapped the injector into cyl 1. Misfire did not follow.



They are definitely bad. It isn't the smell of gas. It's the smell of rotten eggs when WOT and always going over 100mph.
Although I don't get codes for them often. Maybe like twice in the past 6 months?

It does however smell like gas on start up. But I've had this car from almost 11yr and it's always smelled like that?




Yeah no SAP codes at all.
And I wouldn't count vanos solenoids out. I've had misfires and timing issues caused by solenoids before on another car.
After solenoids were replaced. The car idled PERFECT and the startup was smooth as butter.
Being that I did leak/compression test I would assume it should show a bad spring.

I have no reset adaptations though.... I could do that.



Yes after the car is warmed up. I restart it and the issue goes away completely. And the check engine light goes off.



That's what I think to. leak down would show if spring / valve issue.
No I have not checked the coil harness yet. Reason being when I'm watching all coil reactions on the computer they look fine.
On startup and idle and when warm...
A lot of bases covered. Probably wouldnt hurt popping that valve cover off and checking the valve springs anyway from what it seems to me. Maybe a spring on its way out, who knows..
 

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Do this: early in the morning, start the car, you should see water vapor coming out the exhaust , thick white "smoke" that is purely water vapor. If you don't see this, there is a good chance your SAP is dead and not blowing air.
How could SAP (blowing extra air into exhaust) possibly cause a misfire? I'd say barking up the wrong tree here, especially when failed SAP causes codes not mentioned by OP.
 
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