my hesitation is gone but i changed so many things at once i don't know what fixed it. here is what i did maybe it'll help.
2 new opti's - first one lasted about 2 weeks
removed air pump
new o2 sensors (from car quest) last set ac delco
removed egr
new plugs and wires (taylor w/ heat sleaves)
new crank pos sensor
added hooker lt's
new head gaskets
new water pump
new idler pulley on blower

 

Maybe a MAF sensor is bad

 

I replaced my M.A.P. Sensor and it seems to have given me some power back but I don't know if I am imagining it or not. It was always worse in hot weather and its been cold for a while now so it may be some time before I know for sure. Anyone else make any progress on this?

 

you guys should try your cat cans, same problems here. took it
to the dealership cause I thought it was clogged but it turned
out to be the cat can. Might help

 

AFTER ALL THESE MONTHS DID ANYONE SOLVE THEIR PROBLEM?

 

no luck here

 

THAT SUCKS BRO!!!!!!!

 

94 Z28, 84K miles. Why not chime in on the tail end of this one. My 94 runs bad after warming up. It also developed what sounds to be a valve tap. I changed the plugs and it didn't help. After I changed them I rechecked them a few days later and found number 8 loose. I retightened and added marvel mystery oil to the gas and oil. three days later the car ran like a bat out of hell and the noise was gone too. Three months later I stomped on it up to 5 grand and when i got off it it was tapping and running rough again. The low coolant light has always been on. This only happens after it reaches operating temp, and below 2k rpm. I have cleaned the MAF and changed the fuel filter. I checked the valves and the injectors. It has new plugs and wires. Next would logically be the Opti, but after heaing this I might wait. I don't know if they do this everywhere, but in NY they change the gas over to Oxygenated mixture for six months out of the year...

 

Mine has started to get hard to crank. I hope the Ignition Control module fixes it all!

 

Sorry folks to bring back this ol' tread, but I do think many of you are still chasing the infamous low rpm (1000-2000) stumble.

THE PROBLEM IS GONE, HELL YEAH!

After houndreds and houndreds of $$$$$$, many sleepless nights and f*cked up afternoons wrenching under the car, ...
guess what was the problem....!

INJECTORS!!!!

After changing the plugs, some were showing sings of being extremely rich. Some were even "wet". Opened the TB it smelled gas.
We made a datamester log to capture "the moment". To make a long story short, during the 1000-2000 rpm range, when stomped, the engine was practically flooded with fuel. We could even catch an exhaust backfiring and record it on Datamaster

I replaced them with #30 Accel's, GOD, what a difference. And I think Accel isn't even the best brand

Good luck to all of you!

 

thank you good man. god bless you. Did you have the same symptoms as the rest of us? floor it and it sputters until about 2k then it "wakes up" and tears ***? if this truly is the answer to all of our problems, then god bless you good man. amen.
lol, seriously, thank you...

 

LOL, you're welcome, I mean that's what the board and all the people are here for...

Yes, I had the same problem. I found this thread like three weeks ago. I've read every post (300) , and discovered two type of people. One type of them had midrange or high rpm miss, but it's a diff. story (opti,etc.).
The rest (WE) had that 1000-2000 stumble. My car had the following symptomps: once you floored it between 1000-1500, it had absolutely no power, no torque, whatever....but once it hit 2000rpm, it threw me in the back seat and pulled like a SOB.
It wasn't that much noticeable when cold, but when it reached operation temp. it was really driving me nutz.
Then it betrayed itself with a large exhaust backfire at 1200 RPM, at that point I knew it was getting to much fuel.

SO AGAIN, this fix is for the LOW RPM (1000-2000rpm) STUMBLE,
not for the high rpm miss!
good luck,

 

I thought replacing my injectors would have helped but it didn't. I'm beginning to think my problem is internal. Maybe a chain or bent pushrod.

 

ASDFA! I just replaced my O2's hoping it would fix it.. (going to do the 2nd one today) if its just the injectors amen to that! I'll be trying the injectors next... how hard is it to replace them? =] Noob mechanic here hehe

 

Replacing injectors is a piece of cake....I'm an "internet mechanic" myself , and had noooo problems. You don't have to disconnect anything, just unbolt the 4 bolts and yank it out.
When you pull the injectors have some rags handy, 'cause some fuel will leak out from the rail. Just don't be scared and double check everything.