94 Gt With Sensor Problems...plz Help!?

I have a 94 Gt, 5sp., with 87,000 miles that runs like shit when I have the mass air sensor and air charge temp sensor plugged in. If I unplug one or both of these sensors my car will run pretty close to normal except for it doesn't want to idle the majority of the time (loop out). The car is the same below 2500 rpm with the sensors plugged in or unlplugged but when its unplugged it has like a powerband that it comes into above 2500 rpm. When its plugged in and I downshift and bring the rpms over 3500 it backfires and crackles. The check engine light of course comes on when I unplug either sensor. I bought one of those $25 chips things that you plug into the air charge temperature sensor and gives it a fixed temperature reading and it turned off the check engine light. With that chip it pretty much runs the same as it did unplugged except for even poorer fuel economy and alot of backfiring and crackling. I dont have the egr valve tube connected to the header and I dont have any cats but all the other emission stuff is on there. I aslo have cold air, shorty headers, offroad h pipe, msd wires, and an msd blaster coil. People told me I need to have my computer reflashed and that my mass air sensor is probably bad but I wanted a few more opinions before I do anything. Sorry about writing a book but I wanted to be thorough. Any help about what I should do will be greatly appreciated.

I seem to remember someone saying something about taking the smog pump out of the loop if you don't have cats, did the problem start soon after you got the offroad pipe? Have you tried getting a shorter belt to bypass the smog pump?

I could be wrong, and if I am, I apoligize. Good luck.

When I bought the car it was stock and it ran the same as it does now. All the exhaust did was change the sound and the performance gain was barely noticable. I put a toggle swich on the air charge temp sensor so I can open and close the circuit to it while im driving. When I flip the switch while I'm gettin on it it feels like a shot of nos. I've thought about takin off the smog pump since its no longer got any cats to flow air to but I just haven't got around to it. Thanks for your advice and hopefully you can give me a lil more.

I have a 94 GT and mine would die too occassionally when I'm trying to idle after I have ran it hard. I cleaned the mass air flow sensor with a cotton swap and I haven't had it happen again yet and I've ran it harder than before since then. Mine doesn't have any of the other problems but I also don't have the ignition upgrade mine is just an offroad x-pipe (smog pump still attached, haven't removed it yet), flows, and a K&N air filter. You should try that it's a cheap fix if it works

If this car ran like this when you bought it are you sure it was completely stock? Exhaust change isn't going to give you the problems your having. And I wouldn't worry about the smog pump right know either. I think I would start off removing that $25. chip thing. All that does is trick the computer, this just causes the computer to dump more fuel into the engine. With the problems you have that might not be a good idea right now.

The second thing I would do is replace your oxygen sensors. I believe your computer is getting a fault reading from them which may be why your getting backfire.

As far as your mass air meter is concerened yes it could be bad or someone could have replaced either the injectors or the meter and its possible the two may not match.

Sounds to me like you need a new mass air sensor. Do you have a friend or someone that you know that has a mustang so you can try their air meter??? I'd check that out first. Another thing you might want to check would be your IAC Idle Air Control.