unusual miss...any ideas?

[stdavid]

Originally Posted by 4SPEED

more often than not when at a stop and idleing the engine runs ruff. Not like a spark plug missing but definately noticeable. And it may vary in intensity from stop to stop or may not do it for awhile but I never feel anything driving (accelerating or cruising). The plugs and wires are new. I have run several bottles of Techron thru to clean the injectors and carbon off the valves and piston crowns. The compression is 169, 172, 174 and 173.
I'm just fishing to see if anyone has had a similar problem or has any ideas before I take it to a shop and have to hock my wife for the bill. It's an 03 GT with 51125 on the odometer.
Could it be a bad injector to have a problem come and go? Are they hard to replace and what is the cost of one or should you replace all at the same time?

thanks guys

Hi
I just had the same problem fixed in my 04. It idled very rough and and was misfiring. It would actualy stall at times.
My dealer had a heck of time finding the problem. Car was in shop for 4 days.It turned out to be a faulty 02 sensor. That is the one that is after the Cat. converter. Part # 56029050AA
They replaced the plugs and wires but that didn't solve the problem till they located this bad sensor.
The sensor was causing the car to run far to rich.
Hope this helps

[gschnu]

Originally Posted by slartyblarfast

The PCM detects missfires. It doesn't care what causes it it just senses it. Are you really sure concerning the PCM could detect always exactely on which cylinder it happens?* If the gasket is leaking and that cylinder runs lean it can cause a missfire.No doubt about that!

*It is hard for me to imagine how this should be done, but you might be right!
1. There is no "misfire sensor". There is only one knock sensor for all cylinders. There are the O2-sensors but not one for each cylinder. There is no intelligent gasket with built in leak detection. For each cylinder there are only the ignition coils/wires/plugs and the injectors, as far as I know, which are controlled by the PCM.
2. One possibility might be, the PCM checks the position of the camshaft (of course it does) AND relates it to something typical for a misfire (momentary lack of power, signal from knock sensor...) and by that way the PCM can tell where the misfire happens. Is that the solution?

Georg

[4SPEED]

I understand now, thank you so much for clarifying and showing me a picture.....now I can get to work and fix this bothersome problem