Thread: Sputtering 2005 Pontiac Grand Prix

Check engine light is on, and has been for months, because of the EVAP system. Codes it is currently throwing are P0300 and P0446.. I'm at my wits end with this car! 205,000 miles on it. It's been sputtering for a few months now. We just put on a brand new cat, at it is gorgeous! We replaced all of the spark plugs and wires and the vapor canister vent solenoid valve. This morning, it started on the 6th try, thankfully. It was super cold, but I have never had it take so long to start. When it sputters, it will do it between 1500 RMP and 3000 RMP. It doesn't sputter all the time. I went a week without it doing anything and now it's doing it all over again. Yesterday as I was leaving work, it didn't sputter at all! I'm pretty sure I also have a fuel leak, as I am going through gas like crazy lately, but I want to get the sputtering under control first. When it does sputter, the check engine light flashes and it seems like it has a hard time revving up, but once it stops sputtering the check engine light just stays solid. Any ideas? I don't want to just keep throwing parts at it as it will start becoming even more expensive!

that's kinda the same problem I'm having I also have a 2005 gtp mine is throwing p0300 and p0306 ive changed the plug plug wires checked the injectors swaped coils to see if misfire chaged with it did not going to do a compression test hopefully today I think maybe lim gasket but idk let me know what u find out hope fully we can solve r problem together

I really hope so too! I need to keep this car running for as long as possible. We were thinking the fuel pump, but we are trying to avoid dropping the tank, so we are looking at other things.

yea I would like to avoid that to but I defently feel like it has something to do with fuel or spark

That's what we are thinking too. But the fuel pressure is okay, but it's on the low side so we're not too sure.

We have tested all of the cylinders and they are fine. We just changed the spark plugs and wires a few weeks ago. We have checked coils and the ignition control module and all is fine.

Can you confirm the fuel leak? I wonder if at those RPMs you putting just enough load on the fuel system that due to a leak (would have to be pretty extensive) that the car isn't getting enough fuel. I use an Aeroforce Scan Gauge but just a basic OBD2 scan tool with live scanning will do. I an Autel 519 and works great when I rarely need it. Ive used it more to help friends out then myself luckily.

We have almost fully confirmed the fuel leak. We can obviously smell it and see how much I'm going through and how on the low end the fuel pressure is. We're still working on that one.

I did check the spark plugs and wires last night, all is fine.

My car did absolutely fine this morning. Started right up and didn't sputter the whole way to work. I'm so confused with this car!

Originally Posted by GrandPrixGT1

Can you confirm the fuel leak? I wonder if at those RPMs you putting just enough load on the fuel system that due to a leak (would have to be pretty extensive) that the car isn't getting enough fuel. I use an Aeroforce Scan Gauge but just a basic OBD2 scan tool with live scanning will do. I an Autel 519 and works great when I rarely need it. Ive used it more to help friends out then myself luckily.

What whould u look at on the areoforce to know if im getting enough fuel


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