Thread: P0300 multiple cylinder misfire code

Ok, I have a 2001 Grand Prix. It has no power! When I pull off it takes forever to get past 25mph like a couple of miles. It tops out at 2300 RPMS. Then when it gets to about 35 mph it starts acting like it wants to get better then at 40 mph it will take off like its running great. Ive replaced the plugs and wires. I checked that spark is coming from the coil packs. Im thinking it could be the crank position sensor??? not really sure or maybe a O2 sensor?? Any ideas guys? Thanks in advance.

only a scan would help us to figure it out.

the CPS would make the car die, so thats not it. an o2 sensor would just make the car run funny, so it could be this but youd throw a code for it.

Originally Posted by Bio248

only a scan would help us to figure it out.

the CPS would make the car die, so thats not it. an o2 sensor would just make the car run funny, so it could be this but youd throw a code for it.

Thanks Bio248... I did put my fathers OBD scanner on it and had it scanned at Auto Zone as well. They both said P0300 multiple cylinder misfire code and it might have mentioned a code 4?? for the EGR valve. Cant quite remember. It will die will driving at times. I just stop and start it up again and off I creep away. Perplexing to say the least. Maybe a clogged cat???

Ok, I found this info on the internet....... C/P from the internet:

Trust me, the trouble is the catalytic converter. I had all the classic symptoms as everyone else and in the end it was the cat. P0300 is the cat. It causes backpressure to the extent the engine can not fire properly. That is why it does not show up as a particular cylinder misfiring. The engine is firing but not getting full power because it can not exhaust the previous cylinder fuel burn. It is not the secondary air pump, nor the 02 sensor, as I replaced all and still had the problem. Engine would not produce over 2500 rpm in driving condition. Felt lilke transmission was slipping. That is because transmission could not shift because motor was not developing enough power to get to the next higher speed.
The GM special policy number on the catalytic converter is 05551, which provides warranty on cat to 10 years or 120,000 miles. Good luck.

try it out, take off your downpipe and run it down the street to see if it drives better.