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Discussion Starter #1 (Edited)
Guys-

169k
Stock except IATS

70 miles into a 160mile drive, filled up with fuel- sketchy chevron.
45 miles later engine stumbles, 4000rpm... rough running. After 15 seconds SES light.

Next day I checked codes on the Peake:

2C Thermal Oil Level Sensor
E8 Evaporative emissions purge valve functional check’

B2 Catalyst system efficiency, Cyl #1-4"
C4 Misfire, Cyl #1"
CD Misfire during warm-up, Cyl #1
CF Misfire during warm-up, Cyl #3
D0 Misfire during warm-up, Cyl #4
D2 Misfire during warm-up, Cyl #6
D4 Misfire during warm-up, Cyl #8
D5 Misfire during warm-up, multiple cylinders
35 Electronic Fan (relay)

Cleared them...had been a year since I looked at codes...and have NOT had any SES lights... . Drove around- immediate misfiring/rough running. SES in 5 minutes

Misfire 1,6,8 and Misfire during warm up 1,6,8 plus
Misfire during warm-up, multiple cylinders. Repeatedly. No E8 returns, no ebox fan nor cat codes...I think these are noise, all I get returning are misfire codes. (although I am not driving more than 5 miles on these little trials)

(NOTE: I am pretty sure we have established the "warm up" interpretation in the Peake reader is incorrect- there are misfires and misfires with cutoff (or 'cat dmg')

Ordered plugs, fuel pump and fuel filter.... just for the heck of it, bit of a WAG, my schedule is such that I cannot screw with cars right now.

Weekend comes. Change plugs- same issue. Change fuel pump- same issue. Change fuel filter- same.

INPA on laptop to monitor stuff... nothing seems way out of whack (fuel trims, etc) except:



I can reproducibly clear errors and 1,6,8 return as misfires. if I drive it hard, I'll get the "cat damage" misfires as well.

I have NOT yet switched coils.

For reference, I also found this seemingly related thread:

http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/308017-help-unresolved-warm-up-misfires-5-6-3-after-maintenance-3.html


Remember all this started during a drive- NOT after any maintenance, etc.

Bright ideas???


Thanks!


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Did you try switching the coils to see which coil is malfunctioning? Since you are there, I would replace the coil pack as well. It wouldn't hurt to have new ones anyway. Also I would try to get a sample of that sketchy fuel you purchased and test it or see if anybody else is having problems... If it is bad, that's a lawsuit you got... ;)

Edit: I just realized you didn't. Switch the coils for proper diagnosis. You will know right away that which ones are bad.
 

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Discussion Starter #3
I'll switch coils tomorrow, but what are the odds of 3 coils going bad within the same 5 minute period after 165,000 miles?


Question: can one bad coil/cylinder have a 'dynamic' effect with the misfire sensing algorithm and cause spurious misfires elsewhere in the firing cycle? In other words are all these 'real'?

I may just move Cyl 1....where to?

A
 

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Something as simple as bad gas (yes, it should show up after a mile or two of driving and one would think it would affect all cylinders)? No harm in throwing down a can of Stabil gas treatment?

Regards,
Jerry
 

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Sorry to hear of your troubles.

Check for broken/loose wires on your coil ground wires. Some of them are daisy chained. Losing a ground could cause these kind of issues.
 

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Sorry to hear of your troubles.

Check for broken/loose wires on your coil ground wires. Some of them are daisy chained. Losing a ground could cause these kind of issues.

Interesting. That might explain why moving a coil wouldn't help.

Regards,
Jerry
 

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INPA on laptop to monitor stuff... nothing seems way out of whack (fuel trims, etc) except:



->
Are those run unrests at idle? Do they improve or get worse as you raise the rpm? Run unrests should be less than 200 with occasional spikes up to 300 at idle in my experience, like below, and improve as you raise the rpm. So you seem to have a problem to a varying degree with all the cylinders except 5. So certainly not an individual coil issue. And if it’s a common issue like low fuel pressure, why is 1 so bad and 5 OK?

Maybe time for a VANOS test just to rule that out.

INPA10.jpg
 

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Discussion Starter #9
OK.. more info.

Checked Run Unrest at some rpm. Values all drop to ~100 or lower at 2500rpm. Could be just result of how this is calculated, still stumbly.

Checked all wires, ground and tohers, to coils. All good, no pinches, loose, damaged

Swapped #1 and #5 (the two FRONT-MOST coils, correct? #1 is USA passenger side front)

Here is run unrest:



Again, this evens out at 2500 rpm


After warm up I get the following 3 misfire codes:

Cyl 3
Cyl 5
Multiple Cylinders


So from a code perspective, #5 shows a fault- perhaps bad coil. Why is #3 showing an error? It was untouched. Previously it was #1 plus 6&8. Now #5 plus #3. Any thoughts?


Here is the firing order near as I can tell: 1 - 5 - 4 - 8 - 6 - 3 - 7 - 2

Im leaning toward a few coils. Replace that one that was on #1 and is now on #5..... Replace all? Buy 3,4 and see what happens?

Thoughts appreciated.

A
 

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Maybe give Clemster a shout. See if he can send you some to troubleshoot with. I'm sure he has a few laying around.


Sent from AutoGuide.com App
 

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Discussion Starter #11
And perhaps the simplest end to not so long a saga....


Bought a single cheap coil at Napa- $57 for a no-name Altrom part....replaced that coil that WAS at Cyl1 then moved to Cyl5....

here:




The 'multiple misfires' threw me off. I know the algorithm the DME uses to detect a misfire uses 'actual' and 'expected' flywheel acceleration...with one bad coil (ie only one cyl affected) this apparently can lead to spurious faults at other positions?


Anyway, will probably buy a OE/OEM coil or 4, just to have around.

I'll button her up, drive - maybe a quick wash....expect all is good now.

Thx

A
 

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That's crazy! After the coil switch-over, 6 and 8 are still bad, in fact much worse than 5, yet now there are no codes for them! Beats me. But I wouldn’t have expected the misfire detection to be so easily fooled.

I can think of some obscure reasons why maybe it’s picking up spurious misfires when a real misfire is happening, like the harmonic balancer getting old, or the CKPS being loose or it has a loose connection that shows up under vibration, or the rear main brg is worn, allowing the flywheel to move around under misfire, but it’s all academic now you’ve fixed it. :cheers:

I live and learn.
 

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OK.. more info.

Checked Run Unrest at some rpm. Values all drop to ~100 or lower at 2500rpm. Could be just result of how this is calculated, still stumbly.

Checked all wires, ground and tohers, to coils. All good, no pinches, loose, damaged

Swapped #1 and #5 (the two FRONT-MOST coils, correct? #1 is USA passenger side front)

Here is run unrest:



Again, this evens out at 2500 rpm


After warm up I get the following 3 misfire codes:

Cyl 3
Cyl 5
Multiple Cylinders


So from a code perspective, #5 shows a fault- perhaps bad coil. Why is #3 showing an error? It was untouched. Previously it was #1 plus 6&8. Now #5 plus #3. Any thoughts?


Here is the firing order near as I can tell: 1 - 5 - 4 - 8 - 6 - 3 - 7 - 2

Im leaning toward a few coils. Replace that one that was on #1 and is now on #5..... Replace all? Buy 3,4 and see what happens?

Thoughts appreciated.

A
Ard,
What is the Run Unrest measuring exactly? I find it interesting that the #1 cyl had the misfire and was the outlier in the first test, and then in the second test after you swapped #1 to #5, the #6 cyl was the outlier. And yet, you didn't have a code thrown for #6.
 

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Discussion Starter #14
Im not sure, exactly. It is a measure of variability. "run unrest" is a literal translation from german.

There are a few posts here that may have more detail, use the term "run unrest"

I assume the DME looks at acceleration of the flywheel after each ignition, and the variabiluyt from cycle to cycle creates this metric.

Yes, the response to changing one coil...and then the total resolutionm on ALL cylinders with one coil replacement, was surprising....
 
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