Hello all,

Sorry this is so long, I am desperate for help though. Please!

I recently got interested in drag racing and thought my truck would be an awsome project to start out with.

I own a 1998 GMC Sierra Z-71, 5.7ltr w/ dual Flowmaster exhaust from the manifold back. True dual.

Running all stock without changing a thing I ran 11.57 all night on a 8th. My quickest time of the night was 11.42.

I started with the fuel filter and ignition system.

I changed out the old AC Delco plugs to NGK Iridiums.
The original plug wires to AutoLite 7mm, I was going to go with Accel and still am, I just needed some right now.

Stock Coil with the MSD Blaster PN. 8231. Wrong coil maybe. The paper work that came with the coil said that this particualr part was for a '95 to '97 model. Is there a differance between 97 and 98?

Still have the original Cap and rotor. Waiting to change out as well.

Ok, I am have a small problem though.

Last Monday after the plugs and the coil I noticed a sslight misfire coming about, I thought maybe it could be the wires not being to handle the load, thats when I changed them out. The truck ran as smooth as silk till yesterday, She is starting to cut out real bad at 1800 rpms. Anything over and under it is still there, just not as bad. At idle when I place my ear to the passenger side exhaust pipe, about every 6 seconds or so you hear what soulds like an air puff, not normal noise for the exhaust. Left side is fine. I pulled the plugs and the wires to examine and everything looks fine. No burns anywhere, all gaps are ok. I have talked to several ppl about this and no one has any suggestions. I heard from someone it could be a valve not seating right, then someone else said if it was that then I would hear like a ting or tapping noise, motor sounds fine. Not even a light abnormal noise is coming from the motor.

I tried unplugging the batt. reset the ECM, nothing. I am stupmed.

I also tried to plug the old wires back in to see if it could possibly the wires, no change, infact, the sound from the exhaust was worse.

This should not be this big of a problem, it is a chevy 350. The most common motor out. I believe the idle is just a little low than it should be. Oreily's suggested a reflash for the ECM for 50 bucks.

There is no check engine light on so AutoZone would not run their scanner, I think I am going to take it back up there tomorrow and tell them the light is out just to see if it is reporting and code. I think I have heard more about a sensor than anything. All the connections on the motor are good and tight.

Any more suggestions.

 

I think I got it fixed, I pulled the NGK's out and replaced with AC Delco Plat's. Checking the GAP as I installed them. There is still slight mis I think, hard to tell well the crappy roads around here. At idle she sounds as good as the day she was born.

4x4

 

ngk's have a problem with the electrode comming off or lostening up i went nutty trying to figure that one out when it happened to my truck

i run delco rapid fires now