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[Kevin Wood]

I wonder what the fuel trims are doing? Removing power from the ECU would probably have cleared the fuel trims... Then again, if we've checked the live data once we've done it half a dozen times...

[05omegav6]

Where did these coil pacs come from Al?

Got them form the plce you recommended int' midlands. did try 3 different coilpacks at the lakes and all 3 were tested and produced 60,000 volts on 2 and 4, but  only 40,000 volts on pot 6. So them ruled out.

I wonder what the fuel trims are doing? Removing power from the ECU would probably have cleared the fuel trims... Then again, if we've checked the live data once we've done it half a dozen times...

And again at the lakes

New loom in order me thinks...

[05omegav6]

Just to update: car does seem to be idling better overall , no hissy fits tonight , although light is still on. At least I know that the bulb hasn't blown .

I think that perhaps it is probably a combination of the following:

1. An engine earth being disconnected.
2. A wiring fault as a result of being laid up for 7 months, (moisture ingress), causing the voltage drop on pot 6.
3. Possible exhaust valve damage from the destroyed plug.

Next step will be the loom. The valves can wait until the head needs to come off, as I don't really want to break open the engine just yet. Still got the original MAF sensor so might try swapping that back to see if the 0100 stays, not sure how long pattern MAFs last. (Done about 30k) .

[Kevin Wood]

Pattern MAFs have been known to e a bit hit and miss...

Have you done a compression test? (I'm sure you have)

Just thinking that would surely offer some clues if there's physical damage.

[MaxV6]

i think he said earlier that Pot 6 was within 10% of the others....


frankly, that piece of information bothers me....   i'd want it a lot closer than that.....   if something happened valve wise previously, (assume it is somewhere in another thread) i'd strongly suspect something like  a damaged  valve seating , and i'm damn sure that would affect the running to some extent.....   whether it would cause this issue,  on it's own, i'm not so sure....


however, it strikes me that if an exhaust valve is damaged, even if it's just the seating ,  then the emissions light issue would make sense, as the thing will be leaking unburnt fuel mixture on compression cycle....   

given that almost everything else seems to have been prodded and poked , changed, swapped, and tested,   there's not a whole heap remaining....

ultimately,  the holy trinity of Fuel,  Compression, Spark,  are what run the thing, and if it's lumpy and grumpy,  there's going to be a reason affecting their relationship somewhere.....


i'm not up to date with the control systems ,  but in my youth i did used to build competition engines for rally use.....    10% is a LOT more variance than i would ever have accepted on a compression test.

[05omegav6]

Of the top of my head, Pots 1-5 were 9.2/3 and Pot 6 was 8.9, so not that significant a difference .

Thinking that the problem is electrical rather than mechanical because once it starts buggering about, if you turn it off and back on again, 9 times out of 10 it is fine, sometimes for five mins, and sometimes for two hours, no rhyme or reason. It just doesn't like idling when it is damp. that seems to be the only consistancy

Will try the 'old' GM MAF today, as I've not gotten round to that yet

[Dishevelled Den]

Interesting thread Al - hope you have some success later on.

[05omegav6]

Right pattern MAF swapped out with original one.  Left the ECU unplugged for ten, then restarted, light out. Once warmed up light started flashing and started hunting a bit. Turned off and re checked the codes: 0100, 0300, 0306, 0304. Residual codes I think:-\

Had lunch and went for a spin, light still out, running idling OK. Will see what hgappens when I hit the mean streets tonight...

[05omegav6]

http://www.omegaowners.com/forum/index.php?topic=97070.0 Might this have something to do with it