1998 Mustang GT hesitation

1998Mustang

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I bought a 98 Mustang GT about 2 weeks ago and its been perfect except for a few small and pretty easily fixable things. Recently ive had a bad hesitation issue. The car will run fine for say 15-20
Minutes or about 9-10 miles then it will start losing power till it acts like it has 2 step and i cant go anywhere really. If i shut it off for a short time; like afew seconds, it will run fine for about a minute then the issue will come back.

Parts that the previous owner said where replaced / changed. Alternator, sparkplugs and wires, clutch, fuel pump and filter, the gas tank was also cleaned out supposedly as the owner before the dude i bought it from said there was a bunch of crap in the tank
 

garrittpwl

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o2 sensor? You could try to force it to stay in "open loop" by unplugging the front o2 sensors. It may be running well while its getting warm in the "open loop" cycle but then running poorly when it tries to read the o2 sensors. You may also check the fuel pressure when the issue is occurring. Could be a fuel pump dying/starving
 

TTSaleen

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Hesitation can come from a low/bad signal to the computer.
Example - If the mass air meter is not supplying correct voltage, it can exhibit the problem you state. Separately your TPS (throttle position sensor) can be failing and not giving sufficient voltage signal to the computer.
I would start with those 2 items considering all the other parts that have been changed on the car.
You should also check the actual fuel pressure when these problems are happening to ensure consistent pressure readings.

Ryan
 
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1998Mustang

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o2 sensor? You could try to force it to stay in "open loop" by unplugging the front o2 sensors. It may be running well while its getting warm in the "open loop" cycle but then running poorly when it tries to read the o2 sensors. You may also check the fuel pressure when the issue is occurring. Could be a fuel pump dying/starving
The fuel pump and filter where replaced, i got new o2 sensors and im waiting for a good time to install them
 
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1998Mustang

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Hesitation can come from a low/bad signal to the computer.
Example - If the mass air meter is not supplying correct voltage, it can exhibit the problem you state. Separately your TPS (throttle position sensor) can be failing and not giving sufficient voltage signal to the computer.
I would start with those 2 items considering all the other parts that have been changed on the car.
You should also check the actual fuel pressure when these problems are happening to ensure consistent pressure readings.

Ryan
Mass air flow sensor and TPS have already been replaced,
 
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1998Mustang

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how many miles on timing chains could be stretched out enough .
I might of finally figured it out, but imma need to wait for the part to come in, i think after more testing its my fuel pressure regulator. My car was having its issue, i depressed the valve core and my car almost died immediately, i did it when it was “fresh” and it didn’t even think about dieing. Ive also pulled the vacume line for it and it made my issue way worse. But very very similar symptoms. Plus as i command throttle it opens up then let off it might slowly get stuck in the closed position /or whatever makes the fuel pressure decrease.
 

J_lope82

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Verify your diagnosis by installing a fuel pressure gauge and monitor the pressure as you drive it.
 

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