I have a 99 pontiac trans am it just started acting funny.I got a check engine light on and the car has a misfire on lower rpms but if you stomp the gas down it runs fine.It seems to be getting worse as the car warms up.I have just headers,no cats and a borla muffler also their are no rear 02's. The check engine light is saying p0300.I had the car put on a snap on scanner and its saying misfire on cylinders 1.3.5.7 all bank 1. I have had a compression test done and its showed up fine,a wet test also the valve springs looked at.Their are so many posts on here and I dont want to start just replacing plugs,wires,injectors,coils that can get a bit expensive.Please if anyone has any ideas let me know.. Thanks..

 

I can help! Get me the actual message you get from the PO300 code like multiple cylinder misfire or whatever the message says.

 

The "message" for P0300 says Random cylinder missfire detected in all OBDII vehicles...

 

I Fixed The Car. The Front Bank 1 O2 Sensor Was Bad.it Did Not Throw A Code It Was Leaning The Car Out.thanks For The Help

 

I have the same problem. I installed a LS7 in my 1932 pro street truck. And I am running a 400 turbo tranny. Can I just go into the PCM and get rid of the PO300 code so it want come on anymore? Plus is there a difference between the o2 on the driver side & the passenger side? I have headers. So the rear o2's have been eliminated. Mine is a random misfire. The truck runs great, it just gives the code.