i have a 1996 CE LT4. i own the car now about 6 months. about two months ago the check engine light comes on with a code po300(random misfire) i could feel the car stumble at idle every once in a while. i took a look at the opti and found coolant residue from the pump on it, i also checked the wires and found the insulation frayed on the number one wire and a rub through on the number seven wire. so i replaced the wires, plugs, opti spark unit and water pump. the car was fine for a week or so then the light came on again with the same p0300 code. so i replaced the ignition coil and the ignition module. again the car was fine for a week or so then again the light came on again with the same code. i ordered a new crankshaft position sensor and will probably do the intake gaskets too. but i am running out of possibilities here. has anyone had this headache? the car starts up and runs fine. it dynoed at 310 at the wheels and runs the 1/4 mile like a raped date. help help help!!!! could the timing chain be the problem? the car has 50K on it and is very clean and well kept, i am it's second owner. how long do the roller chains on the LT4's last? any problems with the PCM's. any advice will be appreciated. :mad :reddevil :cuss :U this is killing me.

 

I just went thorogh this on my wifes car (sebring convt) but the OBDII codes are the same 300 random missfire 301 #1cyl ect.... Anyway I spent 3 weeks beeting my brains out only to discover I was sold a bad distributor. When I first got the code I figured it was ignition related so I rep[laced the plugs, wires,cap and rotor to start with and it did as you stated ran fine for a couple of days then started missing again, next I replaced the CPS and the distributor and this had no effect. I ended up brining the car to the dealership and they couldn't isolate the problem. I finaly got frustrated and replaced the dist. a seconmd time and it fixed the problem. My guess is that your CPS is fine but if I where you I would go ahead and give it a try then atleast it will be ruled out. But just remember not to rule out the parts you have already replaced. I wish you better luck then I had.

 

I am assuming the car is stock because an aftermarket cam can trigger false random missfire if not tuned properly.

I learned from playing around with tuning the PCM on my car that a rich condition can trigger the code 300. Maybe your O2s are starting to go bad and making the car run rich sometimes.

 

the car is stock except for a K&N filter an open airbox lid, A Granitelli mass airflow sensor, the TB bypass, and an air foil. after i replaced the bad wires i no longer notice the car missing like when it had the frayed plug wires. as for the O2 sensors wouldn't they trip a seperate code? i am gonna try the crank sensor since i bought it already, and i know all too well that new parts can be bad, but the car runs soo well. :banghead:

 

My '96 LT4 CE did the same thing last Christmas season at ~37K.
The P0300 code was all that showed. A trip to the Chevy dealer
involved $$$$ for one new injector and three of four O2 sensors.
I wanted them to put the other O2 sensor in too but they didn't
have but three in stock. Real aggravating for me because the GMPP extended warranty had just expired in Nov '02.

 

ok i'm jinxed. figured i would replace my cps since i had it anyway, and i would do the O2 sensors. the drivers side went fine, but the passenger side O2 sensor took the threads out of the converter with it. i now have a new converter on the way along with a set of ceramic coated SLP shorty headders. looks like i have my work cut out for me and i'm still not sure what the problem is for my P0300 code. also ordered a hypertech programmer because i'm tired of the engine running hot and of hitting the rev-limiter at the track when i go through the traps so i'm gonna raise it. :U :banghead: