I have changed my opti and am still getting a check engine light and some misfiring so t he next thin that is going is my plugs and wires (tonight) but will a bad enough constant missfire cause a check engine light on and OBD1 system?

 

what about a badly fouled plug???

 

nope. The coil can cause it though. Make sure your coil wire securely attached to the opti and coil. And i would replace the coil if you havent. And scan the codes also if you have not yet.

 

More than likely if you have ignition problems and get a light it may because the O2 sensor is polluted and or you are getting a light for being rich. Have you hooked a code scanner to it yet to see what code is tripping the light?

 

yes I have and the code was for a knock sensor circut and the list of what I have changed is as follows:

opti ( GM)
lt4KM
plugs and wires tonight
PCM
coil

 

Start with the code. get that fixed to rule it out. it could be the byproduct of the miss but I doubt it. make sure that the wire to the knock sensor is good and not off, burnt, grounded, cut, shorted etc etc etc..

 

Pcm wires are all checked and good, getting the code cleared is my problem!
the discription of Knock sensor circut is to vauge and I dont know what to do anymore.

 

To clear the code all you do is unplug your ecm fuses. That is not a really good idea until you figure out what the code is. I believe by doing that you are going to dump what ever the computer has stored for the "learned" modes. I would definately try to get the code read before clearing it.

 

I did get a code read and it was Knock sensor circut

 

have you changed the knock sensor? i see you changed the knock module but not the knock sensor.

 

Knock module or sensor whats the diff??? and where on the car is it?? because I have never heard of it, what I changed is in the PCM.

 

The actual knock sensor is in the block on the passenger side. It was pretty easy to change although you will get coolant spilled on you. I know Shoebox's website has a couple of great pics of the location and testing procedures.

 

I ill check in to it thanks Eddie!

 

The PCM sets the DTC code for the knock sensor when it doesn't see the correct voltage in the circuit. Turn the key on, do not start. Pull single wire harness connector off the sensor, and probe voltage from pin on harness connector to the block. Should be +5V if all the wiring is OK. With connector still off the sensor, probe the resistance between the single pin on the sensor and the block. Should be 4,400ohms. If it isn't the sensor is dead or the ground (threads in block) is faulty.

There are no "misfire" codes in OBD-I. The system lacks the crank position sensor required to detect misfires in OBD-II. There are no codes directly related to high voltage side of the ignition.... there are codes for shorts or opens to the ICM and coil, and these cna show up with a problem in the high voltage section of the Opti, but there are no codes for a bad plug, bad wire, weak coil, corroded terminals, etc.

 

Thanks Fred, does anyone have a part# for the Knock sensor by any chance?? (in case I need one)