I have a 96 lt1
Ever since i have had it, i get a random misfire code. I have changed wires, plugs, ICM, and opti. Recently i changed the coil. Since i changed the coil i still get the same misfire under 2500 rpms, but I do not get a error code for misfire. My question is, am i still getting a misfire, or is it something else? How does the computer detect a misfire?
thanks
matt

 

The PCM detects misfires by looking at the pulse pattern from the CKP sensor, and looking for minor variations in the crankshaft rotational speed, that would match the variations in speed caused by a misfire. It needs the use the Opti high res pulse pattern as a point of reference, since that tells the PCM the instantaneous engine RPM.

Could be a faulty CKP sensor, a loose CKP reluctor gear. What cam do you have? An agressive cam can be interpreted as a misfire, since the firing pattern and response of the crank will not match what the PCM is looking for. A bumpy road can cause false misfire indications.

Not sure why you called the topic "fake misfire"..... appears that you are saying you actually have one.

 

i have stock cam, and only 104k on the car. I havent thought about replacing the crank sensor.
I titled it fake misfire, because i am not convinced it is a misfire. What else feels similar to misfire? If the CKP sensor was bad, maybe that affecting the timing, and the misfire is actually the wrong timing(to advanced or retarded)?

thanks
matt

 

The Crank sensor is just for detecting misfires, it is not used for engine timing control, or injector firing. That info comes from the opti.