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One Cylinder Misfire


Xnke

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So I changed my plugs the other day, and noticed that #2 is black and appears oily, where all the remaining plugs are a nice even tan color. This engine has 18,000 miles on it, and has had a light miss since I went to the fuel injection setup. The engine doesn't appear to be using oil excessively, and the head was reconditioned with new valve guides when I had the valve job done. I am using the Ford Capri V6 valve stem seals, and #2 also has an exhaust leak where the manifold gasket is burned out. The leak has black, oily soot emerging from it, instead of the dry soot from the leak in the same spot on #5.

 

I haven't checked compression yet, that is for this weekend. I do not notice any smoking at all, just a light miss that goes away above 5% throttle or 1400RPM. Am I looking at new valve stem seals, a faulted injector, or something more sinister?

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With the oily condition you are describing I would lean more towards the valve seal being an issue, possible oil getting into the cylinder. Check the plug wire going to #2, make sure you have good spark. Also swap it with another wire.

 

You can always swap injectors with another cylinder also, clean up the spark plugs, drive it, and see how the plugs look after a bit. If that cylinder continues to be an issue it may confirm oil getting into the cylinder.

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Tight valves or something else that has compromised compression in someway would be my guess.

Watch the compression gauge on the first two pulses. Low jumps of the needle will indicate a problem even if the compression is close to good on the suspect cylinder.

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Spent some time working on it this evening; Idle up to 1100RPM and pull an injector clip...each cylinder will drop the engine 300 RPM EXCEPT #2. Pulling the injector clip for #2 does nothing at all. Nada. Nothing. No RPM drop, no miss, no nothin!

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Valves are not burned; I checked valve lash yesterday and also did a compression test...burned valves will flunk a compression test if they are bad enough to cause a dead cylinder. Looks like a dead injector.

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Turns out the injector WAS dead, but it had an open coil. Replaced it and the misfire was still there, but now the car smells like raw fuel. The coil pack, which I had previously checked and was fine, turned out to be dead. Cylinder 4 was hitting fine, but cylinder 2 was not. New caravan coil pack and I've picked up thirty horsepower, feels like.

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