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Discussion Starter #1 (Edited)
Hi All,

The car would buck and stutter very intermittently over the last 5 years and would disappear before I could get it to a shop or get it up on jack stands but now the issue is constant.

Hooked up a snap-on scanner and found no codes and nothing seemed out of the ordinary. So after reading threads I started with the basics.

- Replaced Fuel Filter (Which is done every year anyways)
- Replaced the Spark Plugs
- Replaced the Coils
- Replaced EGR
- Replaced PCV
- Replaced MAF
- Cleaned out Throttle Body & checked for Vacuum leaks (none that I could find).

After many failed attempts I borrowed a fuel pressure gauge and hookups and drove around with the gauge sticking out of my hood and found that if I gave it more than a quarter pedal fuel pressure would drop from 30psi to 0psi under load after 2000rpm-4000rpm, and 30psi to 0psi WOT in neutral after 4000rpm.

Now I believe it could be one of these things...
- Fuel Rail Pressure Sensor
- Fuel Pump Driver Module
- Fuel Pressure Regulator
- Fuel Pump
- PCM (ECU)

But I am unsure how to test them or even if I am looking in the right direction.

My baby is a daily driven 2001 Mustang GT (Romeo) , 5speed (T3650) with basic bolt-ons (JLT CAI, 3.73's, Diablo Tuner standard diablo tune, O/R H-pipe, Flowmaster catback).

Hopefully I can get her back to normal soon with your help.
 

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During driving does the fuel pressure change in response to change in throttle or does it stay at 30 PSI?

1st test. If the FRPS intake vacuum line is disconnected and plugged does the fuel pressure go to 40 PSI?

Do you have access to an ODB2 scanner? It would be helpful to cross check the PCM fuel pressure to the external gauge.
 

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Discussion Starter #3
The fuel pressure will fluctuate maybe 2-3 PSI but that's it when giving it any throttle.

I will test the fuel pressure again

I have access to a good one but will the diablo tuner also have that in streaming data?

If not what am I looking for as I am borrowing the tools from a shop and need to return them same day.
 

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Discussion Starter #4
After much troubleshooting found out that the pump was really weak and needed replacement Also the sock didnt look so hot.
 
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