30th TA 0219

ok, some of you may have read this on CZ28, but here it goes.
Bought a 93 LT1 TA M6
Mods are:
Hooker LTs Mufflex 3"-4"Y with Mufflex 4" single
BBK 58mm TB Moroso CAI
LT4 Hot Cam
MSD 6aL
(20k old Opti)
CSR EWP
255 Walbro
Custom tune by local tuner (315/335 NA 445/545 juice)
Also have a PCMforless tune for it, but was told it was less 'drivable'

Has seen some nitrous duty, but not in a while.
Car fires up, idles fine (sounds purely evil LOL) but will brun your eyes if you're right behind it. That being said, I have dual A/F meters inside (non-WB) but they read lean Stoich-Lean, never rich)
Car will run fine when cold, often up to 6500+ scaring women and children alike. Once it gets warm (about 10-15 minutes) the car will not run on its own, it will buck, sputter, and I will have to pump the gas like a wah-wah pedal, just to keep it going. Then, out of the blue, it will run fine under part throttle?
Fuel filter changed, no affect
Fresh NGKs, no affect (wires going on later)
Thinking maybe the O2s are bad, getting replaced tomorrow
Is there some sort of TPS that may be telling the car something is wrong? It runs like you're putting your hand over a carb. Starving for fuel/air, and the meters will read lean and it will backfire.
Is it the obvious Opti issue? Thinking of MSD cap/rotor.
Switch out to the PCMforless program?
Need to get it running right, cuz I'll probably be selling immeidately after it runs right!
PLEASE HELP!!

WhiteSSP

Check the battery voltage. Low voltage will cause the car to runn all crazy, that ended up being my problem last weekend. Car would sputter, backfire, and miss, found out via the scanmaster that I was only pulling 11.5-11.7 volts. Swapped the battery out, voltage came up to 13.3-13.6 volts, and now it runs like a CHAMP.

infinitebird

iTrader: (11)

this was my problem as well.

Also it could be o2 sensors if it runs fine cold but starts to have problems when warm (closed loop).

30th TA 0219

NEW alternator, getting great voltage.
O2s going in tonight I guess. I was holding out for soem GMs from a friend of mine, but may just throw in the Bosch ones I have.

Niteninja

Friend of mine with similar problem. When it stumbles it's throws a SES light then everything kicks in if it is floored. We've replaced the injectors, the O2's, the opti, the ICM, the ignition coil, the IAT, plugs, wires, knock module, knock sensor, MAP sensor, Maf, optima battery, altenator, eliminated air/egr comp programmed and nothing seems to help.

We ran the car with the O2s unplugged, and it still did the same thing. I am out of suggestions, any body??

starts fine, runs until 3000rpms then stutters, sometimes backfires, then 3500 - 4000 it's fine. supposed to idle at 1000, but sometimes dips to 800 and tries to die.

resurrectedz28

My engine did the same thing in my old car. It would stumble/sputter, throw the ses light (never got to see what the code was cuz it would go away after it started running fine again), and a couple of times flat out die when i got on it. When I pulled it to put it in another car I changed plugs, wires, and put headers on it. Haven't had the problem recently. Also I put in a new battery. Dunno if that helps but it might. My car is also a 93 with 148k on the clock.

PS: I know for a fact that my O2's are bad now, ran it with open headers for awhile, and it is running rich as hell because my gas mileage dropped big time. Just some more food for thought, but still hasn't beed doing the stumbling issue.

Might find some more help on this site (Its speed density specific and i have seen this mentioned a few times):http://www.speeddensity.org/

LTSpeed

How many miles are we talking about? There are so many things that cause this. I'm not sure why LT1's seem to see this so much more than other engines.

Two other areas that cause this type of stuff...

4L60E Shift Solenoids or tranny vacuum leaks
Valvetrain issues (weak springs, worn pushrods, plugged lifters, worn rockers)