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[polilara]

Hello

Yes, misfire during idling, no misfire when driving normally. No fault codes. Long term trims equal in bank 1 and bank 2. Short term trims +/-1 or zero when idling normally. When misfiring bank 1 short term trim climbs to +5 or +7 while bank 2 short term trim stays -1 or goes to -2 perhaps -3.

I changed ignition module for bank 2 some months ago due to misfire (spark plug wells full of water). Now I hope bank 1 has the problem this time. I did all the sealing actions needed to prevent water going to bank 2 wells anymore so I really hope it is bank 1 this time (I bought both ignition modules last time as they were quite sheep). What are these short term trims telling to us?

[05omegav6]

To undo the two bolts and pull the coilpack

The trims are simply telling uce that the ecu is trying to accommodate an issue elsewhere, in this case a cylinder 1 misfire.

This will be due to one of three reasons... plug well is full of water (unlikely being the front one), plug well full of oil, and finally, failing coilpack (as bourne out by rusty cracks underneath it)

After all the grief with bank 2, I am surprised that you didn't at least check bank 1... Even more so when you say bank 2 was full of water

[polilara]

Thanks for the comment

Actually last time I checked also Bank 1 for water and oil as I wanted to change all six plugs just for sure. Sorry that I did not mention it. Bank 1 was dry and clean after my cam cover change. But it was some months ago. This misfire just started one shiny day. I was thinking that perhaps electronics just can get old after 220 000 km. I will open the two bolts and perhaps even change the new coil back there if everything is dry, keep you informed.

[polilara]

Bank 1 coil back changed, no misfire anymore. No oil, water etc. found in plug wells (only plugs). Perhaps just age of electronics...

[05omegav6]

Bank 1 coil back changed, no misfire anymore. No oil, water etc. found in plug wells (only plugs). Perhaps just age of electronics...

Any sign of corrosion on the base of the coilpack?

[polilara]

Bank 1 coil back changed, no misfire anymore. No oil, water etc. found in plug wells (only plugs). Perhaps just age of electronics...

Any sign of corrosion on the base of the coilpack?

[/highlight]

I check tomorrow, wait...

[polilara]

Actually yes, corrosion found in those metal pieces which can be seen is small rectangular holes in the base. So, what is this all?

[05omegav6]

Actually yes, corrosion found in those metal pieces which can be seen is small rectangular holes in the base. So, what is this all?

Condensation... water leaking in gets turned to steam... this then condenses on the coilpacks... over time it corrodes, and causes the layers to split... over time and with heat, these separations cause the coil to fail giving you your misfire

[polilara]

Sure, the construction is perhaps not best possible, water really can go through this stupid sealing at least when getting old. Just wondering how this is designed in newer engines e.g. Z28NET. I tried to find it out from google did not succeed. Must be better solution available. It seems that this engine really cannot be cleaned with high pressured water like engines made in 70's...

[05omegav6]

Sure, the construction is perhaps not best possible, water really can go through this stupid sealing at least when getting old. Just wondering how this is designed in newer engines e.g. Z28NET. I tried to find it out from google did not succeed. Must be better solution available. It seems that this engine really cannot be cleaned with high pressured water like engines made in 70's...

Well there's your problem

What made you think it could be

[polilara]

No, I did not do that (cleaning it with my Kärcher) as I read somewhere that it is not recommendable. But it is a pity that you cannot do it. After 200k and after all oil leaks etc. it would be nice  to clean everything everywhere.

[05omegav6]

Ah ok, you can clean it but it has to be done the hard way