ok here is my situation. i purchased a 96 LT4 coupe in april. i love the car but... a few weeks after purchase i noticed a misfire at hot idle followed by a check engine light with a code P0300 random misfire, upon inspection i found coolant residue on the opti from the weep hole in the pump and two damaged plug wires cyl 1 and cyl 7. so i change the pump with the opti and wires and plugs while i was at it. car ran fine no misfire anymore (atleast none that i can feel). a few weeks later the light is back on with the same code P0300. for giggles i replaced the coil and ignition module. again the car ran fine. a couple weeks later the light is back on, same code. so i replace the crank sensor. car runs fine, a couple of weeks and the light is back on again P0300. as suggested by another forum member i swap All four O2 sensors. car runs fine but the light is back on in a couple weeks. the car is not my daily driver i only drive it on the weekends and not every weekend at that. all parts i installed are AC Delco and the engine internals are stock IE cam crank pistons rocker arms etc.. i have heard that some opti's are bad right out of the box, has anyone ever verified this? the car seems to run perfectly, it dynoed at 307 rwhp and runs the 1/4 at 107 mph so i assume the engine is running at 100%. i have a shop manual for the car and it says some causes for this code are out of balanced drive shaft, out of balance tires, rough road conditions or warped brake rotors. i feel no vibrations while driving at any speed and none while braking. and as far as rough road, just about any is rough in this car. i have new eddlebrock shocks on all four corners and a new sport spring in the rear, as well as new universal's on both 1/2 shafts. and new pads and rotors on all four corners and a new drivers side rear wheel bearing, i torque everything down to spec. the shop manual says to use a scan tool for monitering misfire counts, i don't have one is there any way i can do this w/out a scanner? it also says to check injectors using a special tool, again any way to do this w/out the tool? has anyone had this problem? if so what (besides replace the opti) was the problem and if the opti was the problem how was it determined? any help would be greatly appreciated as i feel like i have run into a wall at this point. I would understand if the car didn't run well but it seems to run O.K. a little lope at idle but i think that is the cam, doesn't feel like a misfire. also why can't the ECM determin what cyl is misfireing, i thought that was the whole point of OBDII to help in diagnosing problems. :banghead: :mad :confused: :rant: :sad: :cuss :bs :( :cry :U

 

AS of 1996 the government made it mandatory that all major mfgs. use the obdII system. Before that, techs. had to and still have to have alot more hook up equipment and the knowlege to interpret the differnt systems. That can be difficult, expensive, at times. Point being, obdII has made things much simpler for diagnosis. You need a scan tool...Good Luck...

 

i know all about OBDII as of model year 1996 i was wondering if any one else had a problem similar to this and what the cure was.