[thomth]

Because of a misfire on cylinder 4, with code 29D0, I replaced the 6 coils. I didn’t replace the plugs because the are 20.000km old. After replacing coils the car feels a lot more awake in the low RPM’s.

After 1 week I get a new misfire, again on cilinder 4. It goes like this:
- car feels sluggish, slow in low rpm
- apply more pressure, goes in kick down.
- at 3k rpm the misfire appears, CEL goes on.
- after a few minutes the misfire clears, mostly after just coasting the car.
- car feels fine, can go over 3k rpm without any problems

Only cylinder 4 misfires. No other codes

So I’m in doubt; just replace sparkplugs or also let the injector check? Or maybe the ESS, crankshaft sensor? But then it wouldn’t be logical that only cylinder 4 misfired I think?

And if it was the injector or some sensor, wouldn’t there be specific codes for that parts?

[M-technik-3]

Pre or LCI? have you looked at the connectors that plug into the coils? I had a problem where the connector was not secure enough and would misfire so I repined a new connector. Guess it's not that uncommon.

You have tried swapping coils to determine it, I know you said you replaced all six. What brand maybe you have a faulty one.

[thomth]

Pre-LCI, 2007

I have Delphi coils

I suspect it may be the valve stem seals ;
Oil usage went up last weeks, as did the misfire start…. I did the test with idling for 10 minutes. A light blue cloud came when applying some more throttle. Some time after that, with accelerating , a very big smoke cloud appeared with a new misfire


Valve stem seals and misfires can come together ?

[M-technik-3]

Yes they do. Oil fowl the mixture ratio.

[jadams161]

Replace the plugs. Go with the new NGK Ruthenium Plugs.

[thomth]

I think I’m going to let my mechanic check the valves. I have some feeling the seals are gone; misfire, consumption, smoke…

[jadams161]

Originally Posted by thomth

I think I’m going to let my mechanic check the valves. I have some feeling the seals are gone; misfire, consumption, smoke…

You probably need a valve cover as the pcv system is in it and what you describe can be a failed pcv

[thomth]

Well. The pcv valve with tubes is replaced alongside the DISA valve’s. This was 20.0000km ago

There are multiple shorter trips done with the car so maybe it’s broken again ?

Had some error codes on the MAF a few months ago

Edit: valve cover was 50.000km ago replaced. Don’t know about the seals around the spark plug holes, is it possible to only replace the gasket around the cover?

The coils were clean by the way, don’t about the sparkplugs. Can it be that they are dirty?

[thomth]

So, I called the mechanic. He thinks it is the pistonring on cilinder 4. Because it only misfires on cilinder 4. I’m going to let him perform a compressiontest to be sure. But I’m concerned about my options :

- revision, let it be repaired
- engine swap. Maybe swap it for a N52B30? Might be less expensive than repairing?
- get rid of the car? But sale value is very low now and a
I have done a lot of work in this car
- seafoam? I have read about it here but does it work?