[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…