1998 Mustang GT hesitation

[1998Mustang]

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]

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

 

[96blak54]

Do the 98 have a fuel rail pressure sensor? I know if its faulty, it will cause all kinds of fuel issues.

 

[TTSaleen]

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

 

[1998Mustang]

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

 

[1998Mustang]

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,

 

[1998Mustang]

Do the 98 have a fuel rail pressure sensor? I know if its faulty, it will cause all kinds of fuel issues.

I dont think i have a fuel rail pressure sensor

 

[RAU03MACH]

you do not have a fuel rail pressure sensor.

 

[RAU03MACH]

how many miles on timing chains could be stretched out enough .

 

[1998Mustang]

The fuel pump and filter where replaced, i got new o2 sensors and im waiting for a good time to install them

unplugged o2 sensor and still the same issue

how many miles on timing chains could be stretched out enough .

unknown, would it skip timing after being warmed up? Then shut off and be drivable for afew minutes

 

[1998Mustang]

how many miles on timing chains could be stretched out enough .

Also any other forms of communication? Im actually currently trying to do further diag

 

[1998Mustang]

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]

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

 

[1998Mustang]

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

I cant find a fuel pressure gauge that fits, the last one i had fucked up the treads

 

[J_lope82]

 

[1998Mustang]

View attachment 34645

When i had the fuel pressure gauge on it, it did show low fuel pressure and it slowly went up, like slow af

 

[RAU03MACH]

So what is the pressure now

 

[1998Mustang]

So what is the pressure now

Haven’t replaced it yet as im waiting for the fuel pressure regulator to come in. No place near me has it in stock. Also I’m currently at work, ironically at a shop

 

[RAU03MACH]

after market bbk is good
there are a few out there

 

[1998Mustang]

after market bbk is good
there are a few out there

Mine is the stupid one