Ok. My mom has a 93 5.0 5 sp. mustang LX. She has had this car since it was new. It has been garaged kept and only has 69K miles on it. I usually take it out every so often and get it on the highway and blow it out for her and then check all the belts and fluids for her to make sure things are looking ok. The car is completely stock and has never been messed with. I went to take it out the other day and when i went to romp on it, it picked up for a slight second and then fell on its face. I figured it needed a tune up so i put plugs, wires, cap and rotor. Also a new pcv valve, fuel filter and air filter. Car still does the same thing. I put a fuel tester on it and started it up. The needle SLOWLY rises to around 40 something. It doesnt peg out right when you turn the key on like my other cars do. I replaced the fuel regulator and still nothing. Is it possible its the fuel pump? The car drives fine under normal conditions until you romp on it. and there is that point when you give it to much gas it falls on its face. There is no check engine light on or anything.

I also had the cats checked at the muffker shop and they said that wasnt the problem. Everything on this car is original.

Any thoughts folks? All ideas appreciated. Thanks for reading and the help.

 

How did they test the converters? Short of taking them loose and driving it, they have to use a vacuum gauge to see if they're clogged. Instead of rompming on it, if you gradually try and push it through the upper rpm's will it run fine? I would suspect a fuel issue but You could also have a tps going bad. You will actually need a gauge you can read f/p while driving to see if you're getting enough under load.

 

They used a guage when they tested the converters. It does run good if you ease through the rps and feels good until you hit that point and then it just falls. I put a new fuel pump in and i have it all ready to go. I have to get a new fuel fill neck seal to go in the tank. The one that was in there was cracked and starting to leak. Wont be able to do anything till Monday when i can get to the dealer to get one. I will report back when i get it in and have a chance to drive it. If the tps sensor was bad would it throw a code or a check engine light? No lights are on the dash. Also the guage i have to check the fuel pressure isnt long enough for me to look at while driving. I wish it was so i could see what it read while under a load.

 

you need to find an extension so you can run the gauge out to the hood to see if there is a pressure drop off under load which will indicate arestricted fuel filter or weak pump..also try cleaning the maf sensor with special maf cleaner found at your local parts store

 

I will try that. Like i said i just got the new fuel pump in yesterday but have to wait till i get the new tank fill pipe seal so i can get everything back together and try it out. I will check pressure after i get it running to see if the guage slowly goes up like it did before when you turn the key on. The fuel filter isnt that old but i am going to replace it again before i take it off the jack stands from doing the fuel pump job.

 

Ok got the tank back up and put some gas in it and test drove it. STILL the same problem. running rough at idle and falls on its face when you accelerate hard. So far i have put new fuel pump, filter, and pressure regulator in. Still no engine light or anything like that comes on. I did take it by auto zone and they said they couldnt pull the codes that it was to old. So i just took the sob to the dealer and told them everything i have done. I guess maybe they can find the ptoblem and not screw me to bad. I will post up what the problem was when i get it fixed. Thanks for the help guys, im just tired of buying crap to fix it and still the same problem.