Could it be the MAF?? Please help!!


Asked by Nov 14, 2013 at 08:54 AM about the 2008 Pontiac Grand Prix Base

Question type: Maintenance & Repair

About 5 months ago after stopping at the gas station for a soda I started the car, it was
very rough at idle, put it in reverse and the check engine light came on. It was sputtering
and shaking. I only live 2 blocks away so decided to drive it home. In a matter of seconds
the light started flashing. Next morning I took it to the part store to have them check the
codes. It was a P0300, random multiple misfire, took it to the shop they changed the
plugs wires and a PVC valve. After their little test drive the problem still wasn't fixed.
They then told me I needed to replace the catalytic converter. Not being a cheap fix it
took me about 3 or so months to get that done. Had the new cat put on at a muffler shop.
When he called to tell me it was finished he warned me that it seemed to him it was still
missing. At the part store again got the codes read, still the same, cleared the codes and
drove about one mile before the light came back on. Codes read again for it to still be the
same multiple random misfire. Sometimes at start I have to give it a little tap on the gas
for it to start. The engine light is always on solid and flashing if I go over 30mph. Gas
mileage used to be 22-24 now it's 12-13. Yesterday I started the car and it was shaking
very rough. I now have no power and the car will not go past 20 mph. I had a friend
mechanic suggest it was the mass air flow sensor or the coil packs. Any advise or
suggestions will be appreciated. Thanks in advance. Oh and there's about 160,000 miles
on it. It doesn't leak fluids or overheat.

16 Answers


A code P0300 may mean that one or more of the following has happened: Faulty spark plugs or wires, Faulty coil (pack) , Faulty oxygen sensor(s), Faulty fuel injector(s) , Burned exhaust valve, Faulty catalytic converter(s), Stuck/blocked EGR valve / passages, Faulty camshaft position sensor, Defective computer . Have another mechanic look it over for you to determine what exactly is your issue.

7 people found this helpful.
Best Answer Mark helpful

Thank you for the helpful info. I had to replace the ignition module.

3 people found this helpful.

I'm having the same is that problem with my 2005 Pontiac Grand Prix.what exactly is the ignition module..?The coil packs?

1 people found this helpful.

It's the module that the coil packs sit on. You have to take the coil packs off I order to get to the ignition module. Hope this helps.

2 people found this helpful.

I just started to have this issue.Did you all have any luck fixing p0300?

4 people found this helpful.

I have a random misfire, and hesitation with my mass air flow sensor plugged in... If I unplug the MAFS the random misfire goes away.. Try this until you find your problem

4 people found this helpful.

Things I have changed that still didn't fix my problem MAFS three times, O2 sensors, coil packs, ignition module, IAC, TPS, catilytic converter, lower intake gasket, supercharger gasket, egr, valve cover gaskets plugs and wires, coolant temp sensor, map sensor

4 people found this helpful.

Try replacing alternator, the regulator is built in the alternator and they go bad. You may notice your dash lights flickering, if so. It's the alternator. I pulled mine off and had it tested, passed all test. I replaced it, fix the problem.

3 people found this helpful.

I'm having same issues with my grand prix, did yall find the solutions??

3 people found this helpful.

i have replaces the ignition module and all coils three times now since mechanic knows why. any ideas?

1 people found this helpful.

08gptroubles- thank you, I replaced coil packs and module, it worked. everywhere I took the car they wanted to replace a perfectly good catalytic converter


I've got a 2000 GTP and it does the same thing periodically. Its the number 5 fuel injector that is causing my issue. A bottle of Heat and premium gas (which i try 2 always use because she prefers it for sure) usually takes care of the problem for me. Recently it was sitting for over a year so its doing again but previously i just used Heat every other Tank of gas and it prevented it from happening at all


I was having the same problem (OBDII code P0300 and P0301). I changed the battery, plugs, wires and coil packs the problem still exist. I took it to have the catalytic converter changed out and the tech told me he would do it but in his experience the problem was something else. I decided to wait on the catalytic converter and try a few more things first. When I read this post I saw that the ICM (Ignition Control Module) solved another's situation I decided to try it as well and it was indeed my problem. Bravo and thanks for the help!!

1 people found this helpful.

I have a 2001 grand Prix 2001 and it has a #1 misfire I have changed the spark plugs wires and coil pack even checked the icm and also changed the cat it still misses at times not much other times the hole time I drive it I can't figure out what's going on my next guess is the fuel injector for #1 side cause my macanic said he's checked all the egnishion side and its.nothing on that side it also does this while under a load ex if I power break it HELPME PLEASE

1 people found this helpful.

We changed the plugs ans wire as never had been done but was able to movie coil packs around and found it to be the ignition control module not the catalytic converter! Yeah


Before spending any money check your fuel injectors one by one.....Its free.....Take the little clips off of the plugs that hold the wiring on to the injectors......start your by one unplug the injectors and see if unplugging each one makes your idle rougher if you unplug one that doesnt change the idle at all then replace that injector....if they all function properly then go to coil wires....unplug each one one at a time until u find one that doesnt cause the motor to run rougher.....when u unplug each coil plug wire you should see spark jumping to ground on coil.....if it doesnt then your coil is bad....if they all do then it is your plug wires or plugs.......low cost troubleshooting.....

1 people found this helpful.

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