i need help for my 1995 4.3 cmfi w code engine i replaced cat, o2s,plugs, wires,throttle senor, air temp, cap, rotor, crank sensor but not the cam sensor or the pulsator or fuel pump 118,000 miles on . my scanner says po 300 random misfire, hate that code ! regulator was leaking in intake . put spider in still backfires litltle and still missing . lost ? i heard the heads crack by the valves is this true? i need help !

 

i guess i have the same problem, but i havn't replaced all those parts... this thing just blew my muffler and now i drive the doomsday truck, i need help also! and damn! i don't have access to a scanner!!!

 

Well Butterbean you got the worst possible code there is.
Several have fought it, most do like oyu and start replacing parts, including me. I finally gave up and took it to the dealer. First time it was the cap/rotor. Second time it was 2 spark plug wires. I did a tune up 3 months before I had trouble. Everything worked great until I was 250 miles from home. Then bam, multiple random misfire. I drove it home and jit was a nightmare.

Since you went ahead and replaced all those parts, start there. Double check your work, take it off and do it again. If you went the cheap route, return those aprts and get GM parts. That was my trouble, I got chepaer parts, fortunately the plug wires and cap/rotor were still under warrrenty, I retuned them and paid the extra money for better parts.

taht is my expierience with a P0300.
Search around, you will find other horror stories about it.


Did you replace all those parts to fix the problem, or are you listeing the ones you have replaced recently?

 

hay thaks for reply i relaced all those parts , new muffler, cat, o2s ,spider, throtle sensor, coil , ignitionmodule,egr ,air temp sensor , when put up on my lift i going to drop fuel tank and see if pulsator is bad and pump. fuel filteris new friend of mine has a small shop and i need to check if filter was puton the right way, the flow arrowon the filter body,would that make it run bad ? check the evap canister alsotoo,turn key on pump rus 2 seconds turn off, engine starts up fast. runs ba ba ba poof the regulator was leaking on spider, intake full of gas . 118.000 miles crazy po 300 i have an old snapon scanner aka the brick, red color scanner with gm chrsyler ford software . it helps alot it has too be fuel pump or pulsator i read the old had problems and gm up grade them ? what you think? my blazer has notbeen on the road in 2 years i just relaced all this in about 7 months still in my garage .would pcm say if cam senor is bad i have the code list of po #s ?