I've about had it!!!
 

All right, let me start off by saying this is the most frustrating thing I have ever dealt with. My car started stumbling and misfiring about a month ago but only when i drive it..it doesnt stumble when its idle. So I have replaced spark plugs, wires, vaccuums hoses, optispark, pcm, water pump, fuel injectors, o2 sensors, and did numerous diagnostic checks including half of a dozen obd2 and compression tests and timing checks...and everything clears but i still have a stumbling engine when i start to drive it...does NE1 have NE ideas on this problem...i dont kno what else to do...as of right now all of this work has been done by Bille at Carl Black Pontiac he use to work for GMMG and he has called all of his friends in and called GM tech and everyone is as baffled as we are. Any help would be greatly appreciated.
Thanks
Vince

Re: I've about had it!!!
 

I assume that you changed springs when you installed the RRs? :cool:

Re: I've about had it!!!
 

Did you verify that you have fuel pressure under load?

Did you verify that you have spark under load (i.e. coil)?

Re: I've about had it!!!
 

Is there a way to test if i have fuel pressure and spark under load?

Re: I've about had it!!!
 

To check fuel pressure under load, all you need is a mechanical gauge with a long enough hose to tape it to a windshield wiper so that you can observe it from the driver's seat. ;) Either that or observe it while it's on a dyno.

Re: I've about had it!!!
 

Sounds like the one of the two stumbling issues I had.

1) Replaced everything, but neglected to check the coil because it was only 2 months old. Turned out to be the BRAND NEW MSD coil. Replaced it with a stocker, and all was fixed.

2) After I installed the headers, I had a problem with one of the O2 sensors. I melted one of the wires on the header and this happened to blow one of the fuses titled ENG SEN. This caused the car to miss and drive like crap. When I finally decided to check the fuses, I saw that it was blown. Changed it, and it solved my problems.

Re: I've about had it!!!
 

Fuel Filter is a possibility... I have seen threads where a new fuel filter fixed hesitation. So many things can cause hesitation on our cars though :mad:

Re: I've about had it!!!
 

well i overlooked the obvious guys..and like 1000 bux later ive realized that my damn plug wires were not big enough to hold the current needed...so it was misfiring under load!!! Wow good game to NAPAauto parts for givin me some ****ty plug wires.

Vince

Re: I've about had it!!!
 

What size were they?