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Hello, I have a problem with my 1991 Mustang GT 5.0

471 Views 9 Replies 6 Participants Last post by  mustangguy01
Hello all, I have a problem that I have been trying to figure for about a year now, perhaps someone out there can enlighten me.

I have a 1991 GT that is stock with about 130k on the odometer. The car spent the first 15 years in michigan being stored in the winter. I live in Yuma AZ, and aquired the car a few years ago. Last year the car started sputtering to a stop after being driven more than 20-30 minutes, when the outdoor temps are over 100 degrees. Here in Yuma those temps start around June and end in early october. I've changed out my radiator, thermostat, and flushed the system, yet it still sputters to a stop as if it is vapor-locking. Once I let the engine cool, its fine again. I find this unusual for a fuel injected vehicle. Anyone have any ideas?:headscratch:
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Hiya, welcome to the site. I'll move this thread here so it'll get better attention.

Does the tach jump around when you try to start it?
Do you still have the orginal cats on it? If they are shot it well get worst the longer you drive it.
did the owner have the same problem?and what repairs did he do? I maybe way off base but how about a bad gas cap
Could be your fuel system when the car is started the PCM keeps the injectors on longer because the engine is cold and needs more fuel to stay runnung until it warms up. When it gets warm the injectors don't stay on as long because the engine does not need as much fuel it could be possible that your injectors are not staying on long enough to get the proper amount of fuel in when the car is warm after 20-30 min of driving. You would need a scanner to be able to tell if the injectors are not staying on long enough.
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No, the tach doesn't jump. Some suggestions were that it may be the fuel pump, another was that it may be a fuse under in the engine compartment.
Ibeieve thatthe cats are original, but in the winter when temps run between 60 and 80 degrees, the vehicle runs fine. It doesn't stall at all, even if I run around in it all day.
The previous owner had no such problem. The car was religeously maintaned at the ford dealership where it was bought. On the other hand, even summer temps in Michigan rarely exceeded the high 90's, and since the car only acts up when the temps exceed about 102, it probably wouldn't have exhibited this problem.
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Thanks for the insight, I will have it checked out. But I am curious as to why it only happens when the outside temps exceed approximately 102 degrees. Any time the outside temps are below 100 degrees, it doesn't happen, even if I drive the car all day.
Have you checked your sensors for proper voltage. Maybe even broken/ burned wires. It sounds like it is AIR/BARO related. Are you running any air filter that requires oil?
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