Hi am new to site have a 95 3.8 am having idle problem car starts fine then idles at 2500 rpm this is in park or netural when in gear idle is around 800,Have replaced MAF,TPS,car has CAI, HEADERS, DUAL EXHAUST.Any help with this would be greatly appreciated,Thanks.

 

How many miles on the car? Any accidents; if so, list the things that were replaced. Manual or Automatic. Convertable or Coupe. When it idles at 2,500 RPM, does the engine make any strange noises? More details = bigger chance of solving the problem.

Two things I can think of:

1. The simplest thing to try is: Disconnect the negative cable of your battery and let the car sit for 30 minutes or over a night, watever works best for you. Then, attach the negative cable back to the battery and start the car. This should make your car's computer reset.

2. Exhaust Gas Recirculation Vavle (EGR Valve), but if this is clogged it would cause the engine to idle roughly or ping. Mustang's EGR Valve is vaccum controlled, so if there is a problem with the vaccum lines attached to the EGR Valve, then it could be a an easy vaccum hose replacement. Perhaps some of those lines got torn when the headers were being installed.

I hope this helps...

 

Ah, your car is an automatic, just realized you said neutral/park.

 

Thanks for the input engine has 2200 miles new rebuild all new lines new mass air flow,new TPS,new IAC,new FUEL filter,Already left cable off all day put back on, now car will not run at all starts then immediatly dies,when first started it it ran for about 3 or 4 min idle was perfect, then acted like it starved for gas then died.Anybody have any ideas,I am lost at this point think will most likely end up taking it to a garage.To answer no accidents ,its a coupe

 

Got it running changed fuel pressure regulator ,Now computer is throwing code for bad crank angle sensor.