I’ve had my 2004 mustang GT 5 speed for about a year now and I still can’t figure out this problem. If I drive it regularly and just cruise the car runs fine. But once I go 3/4 to WOT the car jerks and cuts in and out. Sometimes the exhaust will make a popping sound at idle (sounds like it’s missing). Also, on some starts the car will start and die immediately. Other times it will start and run rough for about 10 seconds but after that it’ll run fine.

I’ve done

spark plugs
Coils
Fuel filter
Egr valve
Iac
Fuel rails
Intake manifold

any help I’ll appreciate it, I’m 18 so I’m still learning

 

Any one have any ideas?

 

any codes? engine light on? sounds like a fuel delivery/fuel pump issue.

stop shotgunning parts on it and start with the basics. whats fuel pressure while cranking? whats fuel pressure while driving. Have you scanned it for codes with a good diagnostic device

 

we’ll all the parts I’ve put on it it need them before, except for the plugs and fuel filter. But they are pretty cheap so I just figured I’d try them. I was thinking a fuel issue too. Whenever I put it under heavy load, the fuel pressure drops from around 35psi to 5psi. At idle it’s around 35psi as well.

I’ve gotten misfire codes for cylinders 1,5,6, and misfire on startup code P0300. But once I drive the car regular and just cruise the codes clear.

 

5psi under load? i think you found your issue my friend. replace the pump and filter. dont forget to order a new filler neck grommet before you drop the tank!

 

Thats what I was thinking, I’ll look into it thanks!