I had the classic stumble, under 2000 rpm, the warmer the engine was the worse the stumble. If it was hot enough for the fans to come on you had to be careful from a dead stop not to stall the engine. I changed, coil, opti, wires, plugs, IAT, coolant temp sensor, injectors, fuel filter, air filter, and a few other things that I don't remember. Reset the computer many times. Check a multitude things. The only thing that had a lasting effect was a 160 stat and manual fan switch, keeping it cool helped.
About 2 months ago the battery took a dump, it was about 5 years old. Put a new battery in. Noticed right off the idle was smoother. When it got warmed up the stumble was gone. I waited a couple of months before posting this because I wanted to see if the stumble stayed away. It has been 2 months and still no stumble.
So, well, maybe system voltage at low rpm is not adequate. I checked it several times in the past and it was fine, but this was at idle sitting still.
All I know for sure is I had the stumble, now I don't!!!

93Z M6 RED
B&M Shifter
egr, tbb, 160 stat

 

thats good to hear, I wish it was the case for mine though. I had put in 3 batteries with no change. I think its a exhaust leak. so I guess ill put some headers (sounds so disappointing huh,?)

 

what voltage were you seeing at idle out of the alternator? if you could monitor that

 

Seabat, that is indeed a nice outcome. Change a battery; fix a stumble. I too, wonder what the voltage readings were with the old battery.

Has anyone else fixed such a problem by installing a new battery?

 

I was watching the gauge and noticed the car at idle was right above or below the red so i know the voltage is lower than it should be. I bought a new battery and it didn't change. I took it back 2 weeks later and had it testes and it was perfect. I ran a freescan and the voltage reads 11.9 at idle. The specs are in the 13's i believe so maybe the alternator is bad. I have no power or idle issues but maybe it will run even better when i fix this problem.

 

FYI ive always had low voltage readings in freescan vs a multimeter. I belive our comps are 1-2 volts off when reading freescan