Thread: P0300 and #6 misfire only happens while it boost

New to this forum but not new to the cars. I have a 2000 GTP and just rolled over 150,000 miles on it. I just installed new coolant elbows, Egr valve, pads and rotors, and hub bearings on driver side front. I am not sure if the LIM gasket has ever been replaced with the new metal one. But I Got the #6 misfire code about 2 monthes ago so i replaced the plugs and wires. And just this past weekend i done all the other work listed above. Now i am getting the dreaded P0300 code and the #6 misfire code also. It only throws the code when i go into boost(passing some one on the highway)and while going up hill when the engine is under a good load(like when in overdrive it builds boost when going up hill). so i am thinking maybe the 3/6 coil pack or maybe a vac leak. Greatful for any replies Thanks

Before you buy a new coil you can swap it with another one and see if the misfire moves to another cyl.

Originally Posted by dsmuts

Which plugs did you use?

I agree here too. Several people have reported problems useing platinum plugs in these cars.

OEM AC delco plugs is what I used and I checked all of the vac lines on top of the motor and didn't see any ceacks or breaks. What is beat to use for vac leaks carb cleaner ir starter fluid? The plugs have been invfir around a month and haven't had any problem until now

Ok fellows this is what I got when I changed coils. The 4 and 6 terminal ends on the coil packs was rusted up so I took some sand paper and cleaned them and I have got the # 6 misfire code yet but I am still getting the blinking SES light. It is running alittke better but is still having a slight misfire I will know more this after noon when I drive home from work thanks again for all of your replys

I will check the plug tomorrow but the car is not smoking at all. I switched the coil and it is still throwing the misfire on #6 and the mutiple misfire code like i said above the 4 and 6 terminal ends on the coil pack were rusty and i cleaned them but still the same problem. what is really getting me is that it runs like a champ until you press the gas pedal enough for the supercharger to start building boost and then it starts misfireing. When I took the 2 bolts out of the 2 coil packs i switched the coil packs them selfs were loose(once the 2 bolts where out i just picked them up). < I have never had to mess with the coils so i am not sure if that is normal.

fairly sure i used copper but couldn't say 100% but i am pretty sure because i have already read up on how these engines don't like the platinum plugs. and i had the same #6 misfire code before i changed plugs and after i changed them it ran fine until now(around a month). Could a bad lower intake cause the P0300? the oil looks fine and so does the coolant. Maybe a bad plenium gasket? I just replaced the fuel pump about 5-6 months ago.

around 3 bucks a piece i think they were cheap. How can i tell if the cat is clogged?

when i press on the pedal like to pass some one i get a fuel smell in the cabin of the car but it is not raw fuel smells kinda like half burn exhaust. like it is running really rich.

the engine temp is the same but when you floor it it wants to cut back and sputter a bit