hey all,
I have a 3.4l with the 2.8l intake, dizzy, pacesetter headders, magaflow exhaust and the orginal ecm.
a couple of weeks ago she started missing, now I have just under 3k on this set up. I have changed the wires, plugs check out fine, everthing is tight, ect..

she misses at idel, running at speed, heavy accelatration, light accelatration, food off the gas intermediatly and not every time I drive her. like tonight I drove 2 hours to a car club meetand did not have a singel issue, on the way back she missed ideling at a stop light after she was warm. then was running fine for about 10 mins, then started missing wile taking off from another light, then ran fine for another 30 mins then started missing and died, restarting she started right back up and when I started to tack off missed and died again. There is not codes coming up when I check.

The only thing I have not been able to check is fuel pressure but to me it dose not sound like a fuel problem. any help would be greatly appreaciated.

 

Sounds exactly like a fuel problem to me. Clogged filter? Dying pump? My guesses.

 

i did a complete fuel system replacment (pump, sending unit, filter, lines, hoses, ejectors) when i put the 3.4 in 3k miles ago

 

check it anyways, does the tach start jumping around when it missfires ? if it does its ignition related , on my car when the plug wires started arching the tach would jump up and down

 

yup the tac is jumping, hence why I did the wires and checked plugs and such

 

check cap and rotor and also check all the connections on the dizzy and coil are plugged in fully

 

Take a stethoscope (or long screwdriver near you ear) & listen to the injectors clicking.
Or you'll have to kill each cylinder one at a time to find out where the dead or weak cylinder is.

 

cap is tight, wires fully inserted, pluged in fully and locked in, checked this several times before I replaced the wires and severals times after. this issue is driving me nuts, I wish it would put a code. everything I have tried to do in conection with this has not done anything different, I work with a guy that was a factory certified mechanic for gm, he even gave me somethings to look at and they did not help, I have even started putting higher octane gas to see if that would help.
i can't seam to find anything to make a differance, but the plan is in the morning i'm going to put her in the shop and go through the ingition again

 

wouldn't a weak injector happen everytime it fired or have a loose of power on the engine when its not missing, and the injectors are brand new (well they have 3k miles on them)

 

My bad. You didn't mention it in your first post.

 

I'm having a similar problem, only mine is intermittent. I've replaced everything short of the fuel filter. But my 3.4 injectors didn't look so good when I swapped, so that may be an issue for me as well.

 

well all just went through my ingition, spark plugs are normal, wires are new, cap not cracked and tight nothing abnormal, the rotor i'm not sure about the metal strip for contact is not strait on the end and there is a little bit of pitting on the very end the cap had some carbon around the area where the rotor would be at. any one have any ideas

 

Well all i found the problem she has not missed for two days now, it was the ignition control module. I put the old one back in with a lot of lithium grease under it and no more missing. i hope this helps any one else out there having the same issue