sp103154

Have a 98 mustang GT with this issue: When the car is cold the idle in park and drive is fine and acceleration is fine as well, no noticeable issue. Now, once the engine reaches normal operating temperature the issues starts

1- Idle is rough both in park and drive. needle oscillates between 500/1100 RPM and engine feels like it's going to die.

2- Car accelerates very rough, feels like an engine misfiring (it's not 'cause it's fine when cold), and I have to floor the pedal for it to pick up speed and stop vibrating.

I'm afraid to take it to a shop 'cause I will pay the price again, just took it out of one a month ago after 5 day diagnostics/$1289.00 and all it needed was a fuel pump in the end. Hope not to have to go that route again....

Already cleaned the throttle body, cleaned MAF, replaced AIC and plugs.

Any real good ideas?

Thanks

wmfateam

1: Is there a check engine light? Have you scanned for codes?

2: Can you hear any whistling sound under the hood, aka vacuum leak? EGR hoses, intake boot, PCV...

sp103154

No, no codes or light. Never had a check engine light in 15 years. There are no vacuum leaks, EGR is not stuck, PCV is not stuck and was replaced last year with the air filter

wmfateam

How soon did it start doing this after you got the car back? What were the original symptoms?