Donald Garland

Getting a code Po300 which is random misfiring

Frank3

I got that and a couple PO304s in my 2001 Impala when I had it. In my case, the ignition module (under the 3 coil packs) went bad BUT ONLY when it got hot after 5+ miles of driving. It eventually went from multiple misfires to the PO304. It was at this point with a tester, I could determine there was no spark at cylinder 4. Just as a test before buying a new coil pack, I swapped the coil with another cylinder pair and 4 started firing and the one that was working on cyl 1 stopped.

How is performance of the car? This could also be caused by a plugged fuel filter (engine not getting fuel) or even a plugged catalytic converter which my 2001 Impala had a couple years earlier.

Donald Garland

Thanks for your reply, I have about narrowed it down to the module,but that thing is about $130. I have replaced the plugs,wires, MAF sensor. Sprayed water on the coil packs to see if they might be failing. The car has over 240k miles and still runs pretty good. Will let you know what I find.

Frank3

When I bought a new ignition module at the parts store, I was given the option of the GM module with about 1 year of warranty at about $ 300 or the aftermarket module with a lifetime warranty for about $ 125. I ended up going with the aftermarket module and it was all good until I sold the car some 3 years later.