'02 GT 4.6l High Fuel Pressure, Rough Idle, Loss of Power


New Member
Mar 25, 2021
Hey everyone, I've been slowly rebuilding a '02 GT convertible TR3650 that's been in our family for some time and was a bit abused by salty roads up north.

One of the major casualties of it's time in those conditions is that the mufflers have fallen off. I basically have the two pipes connected at the H so the exhaust needs to be touched up... It does sound awesome though.

Order of repairs so far: replaced Fuel pump allowed car to start and run, but it was sitll going limp mode, come to find out it was the FPDM connection being lose. put a zip tie around it and that fixed that problem. Car was pulling to one side and felt really hesitent, brakes were sticking and suspension was completely shot anyways. Replaced all that to smooth all of that out.

Now, my issue is that the car runs very well cold, but I am in south florida and what the hell is cold. When the car warms up, it appears as though the fuel pressure rises with intake air temp. It will stay around 40psi under cooler/normal conditions of about 80-90F intake air temp, but when sitting idle at a light or if it is really hot out, intake air temp goes over 110-150 and the fuel rail pressure goes up to 50-60psi and the car runs like complete crap.

I recently changed the sparks and coil packs, cleaned the throttle body and IAC, previously cleaned the MAF, thinking this would help. It made it run like a champ for a few miles but it's back to it's same issues.

Basically, right now I am dealing with rough idling and more importantly loss of power, and I am not sure where to turn next. It seems to be related to the increased fuel pressure under high temps, but I'm not sure how to really diagnose this.

I have tons of logs (basically run logs every day I drive the thing) and tons of pictures and videos I can post of whatever if necessary.

Also... Forscan is telling me that there is a Fault on Keep Alive Memory Power and "error" for Fuel System Status Bank 2.. not sure if these have anything to do with any of this, but they stood out as well for being "odd".

Thank you all for any insight you can provide!
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