Engine stumble below 2000 r's

[jdawg454]

Hey guys. Ive never posted on here before but ive done a lot of research and i cannot for the life of me figure out this problem... Im stumpped! I have a 94 Trans Am, 5.7 auto.
Here is what its doing: when it is cold, it runs fantastic. punch it, lights up the tires from idle at a stop. But as soon as it hits 160 degrees or so it acts up. when it warms up it cuts out really bad but ONLY below 2000 rpm's. It will pop and sputter. But you get above 2000 r's and it runs like normal. untill a few days ago. now it still does that, but it seems if you get it to stumble and try to accelerate up through it, it cuts out all the way up. but if you let of and stab it again, it seems fine. im really at a loss here. Parts replace within last year (i know just cuz they are new doesnt mean a thing)... New opti, plug wires, O2's, TPS, MAP sensor, EGR valve, Aeromotive FPR, and im sure other things im forgetting. Pressure measures ok. it sits at about 43 running and you hit the gas to WOT (or take the vacuum line of) and it goes up a bit. 48 maybe. so that should be fine. I just dont know if it is a fuel or ignition prob. One thing is this: checking the fuel pressure, turn the key on it jumps up, but drops to 0 right away. which makes me think the anti drain back valve is gone. any ideas anyone? If there is anyone in MN with a scanner or something like that, ill pay you for you time if you can help me out...

[93fbodcamaro]

sounds like fuel pressure what is it when its runnin down the road

[jdawg454]

It runs consistantly at 43, until WOT then it jumps up real quick to 48ish i think.

[93fbodcamaro]

could be plugs and wires ....or injectors

[Lyle A]

Do you have access to a scaner to monitor data from the sensors. If so, look at the O2's once it goes into closed loop. Also, look at all the other stuff and sure it's in specs.

[jdawg454]

Wires are Moroso, replaced not too long ago. Doesnt mean they are perfect. I just got a hold of someone who has a scanner so we are going to look at that tonight. see whats going on. i noticed when it is cutting out and missing at the higher RPM's, i hear a lot of pre-det. so thats someting that has to do with ignition i would think. but ive been wrong before. i guess we'll see. is there anything specific to look for? i guess this guy is pretty good at what he does so i hope he can figure it out.

[jdawg454]

Problem solved! Finnally!!! A small word of advice in case you didnt know. NEVER use AC Delco plugs of any kind, especially the double platnums. Horrible plugs. the little platnum pieces fall of the plug and shoot out the exhaust, then causing your gap to go from .050 to anywhere from .060 to .070. car doesnt like that too much. that happened on 7 of 8 plugs in less than 20,000 miles. at 6 bucks a plug, what a waste. 60,000 mile plugs my a$$. oh well, just a good reminder, just cuz parts are new, doesnt mean its good. thanks for the help guys.

[94greenbandit]

Good to hear you found your problem. Those problems that are masked by other things are always a pain in the butt.

[93fbodcamaro]

use ngk tr55's

[jdawg454]

I was told to use ngk TR6's. but then i heard a guy with the LT4 head and cam package with nitrous, so im beginning to think i should put a different set in. still doesnt run perfect, but a new set of wires and a tune should help out a bit. so tr55's would be a better plug for a stock motor then?

[93fbodcamaro]

yeah thats what im runnin.........but thats my opinion .....opinions r like asshol*s everyone has one and they all stink