I have a 2002 Silverado Z71 that is misfiring on the #3 cylinder. I swapped the coil pack on that cyl with the one from the #1 cyl, still got a P0303 code. I also swapped the plug wires from the #3cyl with the one from the #1 cly still got the P0303 code. So I know my coil pack and plug wires are good. I replaced all the spark plugs awell and am still getting the misfire. Anyone know what else I coud check that might be causing this?

 

Is it a dead miss? I'd be for checking the compression.

Allan

 

I don't know if it's a dead miss, my check engine light starts blinking when my rpm's get to 4000+.

 

Could be an electrically failed injector or a plugged injector. Might try some Techron or seafoam to see if it clears up, or have an injector balance test run. If not an injector in could be internal to the head.

 

Well, I took it and had the check engine code checked after I put new plugs in it and it didn;t throw a misfire code. In fact the guy said it had no code at all even though I had a flashing check engine light after the new plugs. I did talk to someone that said the engine should shut down if I reved it up past 4000 rpms. I was able to get 5000 out of it while in neutral. He said i needed to have a crankshaft relearn done to it.