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Discussion Starter #1
I'm hoping I've narrowed my over fuelling problem down to the valve guides, please confirm if you think this is viable.

Details:

I swapped Bank 1 Spark Plugs to Bank 2 and vice versa, the problem swapped from bank 1 overfuelling to bank 2 over fuelling. (based on the readings from the obdII software - short term fuel trims)

I fitted new plugs all round and the problem was fully sorted - took it for a drive and 10 minutes later the problem had returned on bank 1.

Inspecting the brand new spark plugs, Cylinder 3 was covered in oil.

So there is poor oil control on cylinder 3. As I take it this is either piston rings or valve stem seals.

If it was piston rings I presume it would chuff out of the oil filler hole and dipstick tube like a 4 cylinder would?

So this leads me to the valve stem seals.

Does this all sound plausible? Spark plug gets covered in oil and starts to missfire - this causes unburnt fuel to be sent down the exhaust which makes it seem as if it's running rich. When the new plugs had just been fitted the idle speed was 750rpm - now it is 650ish and that is where it has been during all the faults.

So my next job is to find some rope and have a go at swapping the seals. Does it sound likely to fix my problem!??

Cheers
 

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Worn stem seals are not going to be your problem,even with no seal in place you would not get a fouled plug in a 10 min drive - just a puff of blue smoke.To oil up a plug like that its going to be coming up past the rings.As long as you are sure its oil and not fuel thats what its going to be.
 

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Just a Suggestion but have you tried Swapping over a couple of Injectors to see if that moves the Problem?

Cheers
 

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Discussion Starter #4
**** was hoping I'd found the solution!

I'm pretty sure it's oil - it doesn't smell too much of fuel (does a bit) and it's black and wet, when rubbed off onto my finger it looks brown.

I've managed to do a compression test on that cyclinder, I only took the one plug out though - does that matter? First test gave 160 psi, I then reset the guage and let it turn over again (I'd removed fuel pump relay) and I got 150 psi.

Do those compression readings help with the diagnosis?

I figured if the piston rings had gone that the pressure would have dropped? Also would the engine chuff from the oil filler if they had gone?

Col I'd thought about swapping some injectors, but wasn't sure how easy it was and if anything special had to be done as it's under pressure?

Any other thoughts

Cheers
 

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Discussion Starter #5
Here are a couple of pictures of the spark plug which is getting fouled up. I probably ran it for 10 mins on the drive, then went for a trip round the block, revved at the point where I turned round for a minute or two, then came back and had it running for a few minutes - so probably a bit more than 10 mins but not a great deal longer:

[attachment=1:1bhgcmqh]sparkplug.jpg[/attachment:1bhgcmqh]
[attachment=0:1bhgcmqh]spark-plug.jpg[/attachment:1bhgcmqh]
 

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