SmokinHot98

iTrader: (20)

Last friday I put in a post seeing if anyone had an extra coil pack laying around b/c #5 coil went out on me. Well I replaced it with one from GM and my SES light is still on and the car is still missing. HP Tuners says its code P0300-Engine misfire. I checked ALL of the plugs to make sure they're plugged in and all the other coils are firing. What else could be causing it to miss?

thanks
Nick

Luna

iTrader: (6)

Do you have the harness on the right way? If you put the wrong harness on the wrong side they won't fire in the correct order. The cylinder # is labeled on the harness near the actual plug for each coil pack.

Just an idea

Pro Stock John

iTrader: (34)

What have you changed recently? P300 is a misfire code that you can get from cam swaps and from air leaks. Did you do ported TB, cam, or !egr or !air recently?

SmokinHot98

iTrader: (20)

I bought the car in July w/118k on it and right away I did !EGR,!AIR(partially i have yet to remove just turned it off via HP TUNERS), plugs(NGK TR55), Msd 8.5 wires, lid, and K&N filter. Then I parked it for the winter in november. I pulled it out of hybernation in the beginning of Feb b/c of emissions test but I failed b/c the system was reset due to a dead battery. And just recently I have had problems with the idle. A few weeks ago I went to the store and it was fine but the next morning it would idle REALLY HIGH and just kept climbing so I unplugged the TPS sensor and it was fine. i bought a new sensor then parked the car for a week. This past friday I drove the car to work and it was fine but in the morning AGAIN on the way home it threw the code and was missing. I got home found out it was a bad coil replaced it and im still missing. I was on the highway when it started to miss though. I went maybe 10 miles like that.
Im just stumped I've checked all the plugs its getting spark from every coil.