Cylinder 4 - NO JOY. Replaced spark plugs, wires, and coils

[red rider]

Seeing how my car has 190,000 miles, I don't feel bad about replacing the spark plugs, wires, and coil. HOWEVER, this did not fix the problem. I can start and run the car from cold with no problem. But, wait 10 to 15 minutes and start up again from hot: There is the problem. The car idles like a '69 Camero with a suped-up small block. The car rocks and the idle fluctuates. If I try and run the car in this condition, it will try and stall at idle. I've narrowed the problem down to cylinder 4 by pulling the spark plug wires one at a time. The coil and wire charge, so there is no problem with the wiring to the coil. MY NEXT GUESS WOULD BE THE FUEL INJECTOR; eventhough I am not getting a computer code for the fuel injector. Or any other code for that matter. ANY GUIDANCE? Red '95 318Ti

[red rider]

I know now that it could be anything from the fuel injector to the DME. Hopefully, only a fuse (cost and all).

I need some input. WT........

Red
'95 Ti

[JNCoulombe]

Have you tried to narrow the problem down to one cylinder? If one cylinder is missing, when you disconnect that cylinder's plug wire the idle will stay the same while disconecting a cylinder that is not missing will markedly worsen the idle. It may be a problem across all cylinders but if it is only one you have simpified the diagnosis.

[red rider]

I narrowed it down to specifically Cylinder 4. I know the Cylinder number does not solve the problem. But, it does show that the problem affects only one cylinder. The bigger clue I am looking for help for is the fact that the car runs fine from a cold start. I feel that there must be a short somewhere once the car is hot. My concern is whether it is as simple as a fuse or wire, or whether it sounds like a problem with the DME?

Any input is appreciated.

[JNCoulombe]

Sorry, I missed that you had already narrowed the problem to cylinder #4. To me the missfire occuring only after the car is warm suggests a fuel problem is most likely. The cylinder may fire when the engine is cold since it should be recieving a richer fuel mixture. When the mixture is leaned out that cylinder may not be getting enough fuel. It still could be a plug or plugwire but that seems unlikely since you replaced these. and hopefully correctly adjusted the plug gaps. I would suspect a partially plugged fuel injector. You could try swapping the fuel injectors to see if the problem follows #4 injector. If your valves get noisy it could also be a lifter collapsing as the oil thins, but the injector seems most likely.

[red rider]

I really appreciate the input. I'm leaning toward the injector myself. Unfortunately, I've not had to deal with injectors before; so I took it to the shop. If it's the difference between a good cleaning or a new fuel injector, I'll take a good cleaning. Although, the cleaning plus labor might cost as much as me putting in a new one.

One step at a time. I'll see what they find.

Again, thanks for the input.

Red