I have a 1991 Firebird Formula L98 just put new plugs cap button and ignition module on idles fine but when I put it in gear and go it starts to miss and when I stomp it, It tries to go but just losses power. and then starts to idle rough. I have checked for vac leaks and fuel pressure is good.

 

What were the pressure numbers, both standing and running (vacuum/no vacuum)?

You might want to measure the resistance of each fuel injector, both cold and hot (after the engine has been running 20 minutes). The Multec injectors which should be stock on your engine are notorious for insulation failures.

 

We found the problem the intake gasket was blown

 

ok blown intake gasket has been fixed and new tps sensor new coil plugs wires cap button complete intake gasket set still not right I can go less than 1/4 peddle and when i floor it, it losses power I am out of ideas need some help

 

what is your fuel Pressure

 

about 46 idle 50+ when I put it to the floor

 

sounds like it might be to high... the injectors wont open if it gets to high...

 

It will idle and free rev fine but when you put it in gear and try to drive it that is when it starts acting up

 

adjust fuel presssure down to 43 idle 47 full throttle see what it does, bet it runs better,later jimmy

 

How did you find the intake gasket bad? I am facing a similar problem but mine is intermittent. Is it possible to have good pressure but low flow? Bernoulli's theorem? What is a good way to check for vacuum leaks?

 

I found the intake leak when I noticed some coolant seaping form between the head and the intake as far as vac leaks you just have to check all the vac lines thats the only way i know

 

Does anyone know if the ecu could be causing my Problem

 

I have changed out the ecu now still having the same problem it gets worse as the engine gets hotter and eventually it does not wont to run at all I am totally out of ideas can someone give me a suggestion

 

the same exact thing happened to me when I first bought my car. I chased the problem for about a week, then found that 2 fuel injectors were shorted out. It would misfire occasionally. the problem got worse, until, like you said, any more than about a quarter throttle, and the car just idles really rough down the street, when in gear. Only it happened in Park/Neutral as well. Measure the resistance of each fuel injector with an ohmmeter. I think that there supposed to have around 14-17 ohms resistance. I found 2 were at like 7 ohms, replaced them, and it was fine. then it started missing again, and i found that 2 more were bad. At that point i just replaced them all with a set of holley injectors. Good luck, I hope that this helps.
-Tom

 

The injectors worked thanks for the help everyone