pettsir

i also have a post in the general forum so i will give the abbrieviated version. bought my 96 LT4 in april. developed a misfire at hot idle with a check engine light on and a code P0300 random misfire. found coolant residue on the opti and two bad wires. replaced the pump opti plugs, car no longer misfires but light still comes on every few weeks. have since replaced the ignition module, coil, crank sensor and all four O2 sensors. again light is on every 2-3 weeks. car isn't my daily driver, only driven on weekends and not every one at that. my shop manual says rough roads or tire vibrations or brake vibrations or drive shaft vibrations could caouse this. i feel no vibrations while driving or stopping. the shocks rotors pads rear spring rear universal's on both 1/2 shafts and L/r wheel bearing are all new. all are a/c delco parts, and everything is torqued to spec. the engine seems to run fine it dynoed at 307rwhp and runs the 1/4 at 107+mph. what am i missing? :mad :cry :confused: :banghead:

96GS#007

You mention two bad plug wires, but make no mention of replacing them....only the Opti, plugs, coil, etc. Replace all the plug wires and the coil wire and be sure to verify they're all fully seated. If you've replaced the wires, have the injectors flow checked. It's very unusual, but you could have one that's bad or partially clogged.

MSR

the misfire occurs only at idle? do you ever cruise in the 1500-2000 rpm range, and if so, does it ever trigger when doing so?

-michael

pettsir

yes i replaced the plug wires. the misfire originally occured at hot idle, that was with the bad plug wires and that was the first time the light came on. now it only seems to come on during cruise with the engine somewhere around the 2000rpm range in sixth gear. it doesn't pop on every time i'm cruising though. wondering if it is a three failure code. any ideas on this??

HWoods

Had a similar issue with my Silverado pick up, tps replacement seems to have cured it. I also replaced the fuel filter