Thread: Help!! '01 GTP misfiring/idiling rough at startup!!

First off, i had an issue a month or so ago w/ the car and it was acting similiar to how it is now. Ended up being my MAF. The one on the car read "0".

Now, it's starting to act up again. When it sits overnight or for a long period, when i start it up, the car runs rough and i can hear it misfiring. Normally, i'd just wait for 30 seconds or so, and it'd straighten out. This morning, it was doing the same thing, but worse. I had it running for a few minutes and it was actually missing more and it never straightened up. I ended up taking my other car to work. I have a new set of jacobs wires, plugs and my coil packs off of my '01 GT, which had 47k on them. I plan on changing them once it's nice enough outside. Are there any other explainations for my car running this way? Maybe another sensor or something else?? Let me know what you think. I took a video of the car from startup a few weeks ago, but it started up fine, go figure. I'll try again this weekend to post a video of it. Now, as far as the video goes, should i be right behind the car, or back about 10' or so, so that the car can be heard better? The last video, i was behind the car and you couldn't really hear how deep the exhaust is.

Jason

Do you have any codes that the SES light is set on the dash? If so...what are the codes?

But it could be a lot of things...anything from a bad O2 sensor, plugs, wires, vacuum leak, etc....Need some more info I think.

Originally Posted by Zef_66

Do you have any codes that the SES light is set on the dash? If so...what are the codes?

But it could be a lot of things...anything from a bad O2 sensor, plugs, wires, vacuum leak, etc....Need some more info I think.

No codes. Put a new denso front O2 in last fall when we put my tog's on. Plugs were installed last may at intense, after i got the GTP. When it does this, it goes for like 30 seconds or so, then straightens up. No issues after that, unless it sits overnight, then it does it again, then is ok. Sometimes, it starts right up w/ no issues at all. Hope that helps.

Jason

Originally Posted by fatride99

No codes. Put a new denso front O2 in last fall when we put my tog's on. Plugs were installed last may at intense, after i got the GTP. When it does this, it goes for like 30 seconds or so, then straightens up. No issues after that, unless it sits overnight, then it does it again, then is ok. Sometimes, it starts right up w/ no issues at all. Hope that helps.

Jason

Try unplugging the MAF before you start it some morning when it is cold and see if it still does it.

Originally Posted by turbocharged406sbc

sounds like a possibility that the FPR is leaking fuel into the LIM overnight, pull the FPR vac line off and smell for gas/wetness.

What does that look like? Is it the round disc looking part on the fuel rail? I have another fuel rail w/ fuel injectors from an '01 GTP w/ 50K on it at home, that i might swap out. I think that i'll need the tools to remove the fuel line from the rail, what's it called and where can i buy one at?

jason

Originally Posted by Zef_66

Try unplugging the MAF before you start it some morning when it is cold and see if it still does it.

Just replaced the maf about a month or so ago. If the maf is bad again, i'm gonna get pissed. I've got a gen.V at home w/ an ls1 tb and a SLP MAF that i might end up putting on if this continues.

Jason

Well, i started my GTP up last night (2/4). It was still idiling rough and this time, it threw a check engine light. I was taking a movie of the car, but it was too loud for my camera to pick up clearly. I did however open the hood and you'll never guess what i saw. On the back side of the motor, i saw a blue glowing light, from i assume a plug wire or plug. Needless to say, i shut the car off after that. Weather was crappy today, so i wasn't able to work on the car. I would take another video of the car arcing, but i don't think that'd be a good idea to do. I'm gonna change the wires and plugs to see if that fixes my issues and i'll keep you up to date.

Jason

Originally Posted by turbocharged406sbc

if your refering to a 99+ rails assembly with the pulsation dampner no thats not the disk, the fuel pressure regulator has a vacum line running to it from the vac tee at the LIM under the snout, remove the vac line and smell it if it smells like gas the diaphram in the FPR is leaking, this is the same issue that causes alot the the NA 3800 engine fires since it's possile for the engine to backfire and set the fuel in the LIM on fire...

I'll make sure to look at that before i start her up again.

Jason

Yeah, the arching is a classic sign of a bad spark plug wire. And that would surely cause a miss. Get the plugs and wires changed and see how it acts.

Also, from the looks of it, you have headers. It is a common problem for the middle spark plug wire on the back side to rub against the header and cause it to burn and short out. When you install the new ones, make sure that all the wires area away from hot surfaces.

Originally Posted by Zef_66

Yeah, the arching is a classic sign of a bad spark plug wire. And that would surely cause a miss. Get the plugs and wires changed and see how it acts.

Also, from the looks of it, you have headers. It is a common problem for the middle spark plug wire on the back side to rub against the header and cause it to burn and short out. When you install the new ones, make sure that all the wires area away from hot surfaces.

Thanks!! Yeah, have a set of TOGs. I do have the intense boot shields on the plug wire ends, but that's below the headers. I was gonna get some wire looms anyways, but this will make sure that it don't do this again.

Jason