Hard to start

[BigOrange]

I have a 93 Fox (motor is completely stock except a 70mm TB and K&N) and it struggles to start whether cold or hot. It takes about three seconds to start. When it does start there are no other problems while it is running except it idles at about 650 RPM. This has been going-on for about a week. I changed the plugs today (.054). The old ones were a little grey but not bad.

Another problem, which may or may not be related because it has been doing this for about two months, is when the car starts it idles to about 2,000RPM until I put in gear and drive about 10 feet. Then it’s back to normal until I change gears. In between gear changes, the idle pushes up to 2,000. I usually shift at 1,500.

If you have a link, please attach with instructions as I have been out of the 5.0 field for ten years. Thanks.

 

[4valvemach]

When you say it struggles to start do mean
a)its slow to crank over like in a bad battery type of problem
b)it cranks over freely but the engine does not fire up

For the other part of your question I am a little confused at what your saying.Are you saying it idles high at 2k rpms when started then when put in gear the idle drops to 650 rpm?I ask because you say it idles at 650 rpms at first then it idles at 2k rpm in the secound part.

In any case I had the same problem on my 93 f150 with the 5.0 engine and auto trans in it.It would idle at 2k rpm at start up and drop to around 700 rpm when in gear.I fixed the problem with a new TPS(throttle position sensor) started it up ran perfect.It is on top of the throttle body held on by two screws.

1989-93 Mustang 5.0L Motorcraft Throttle Position Sensor (Tps Sensor) at LRS - Same Day Shipping!

^^^Just a picture so you know what Im talking about

 

[BigOrange]

b)it cranks over freely but the engine does not fire up until after three seconds.

The hard starting has only been happening for about a week. Prior to that, it would rev to 2K (after a normal start) until I put the car in gear and moved 10 feet then it would drop to normal revs. During a shift, it would rev up to 2K.

Now it is hard to start (hot or cold). It cranks, plently of juice, but either no spark or no fuel for three seconds. Then she starts, revs to 2k until I move the car, then the revs drop to 650. Anytime I shift gears, the car continues to rev to 2k until I release the clutch.

Thanks for your help. I'll replace the TPS and go from there.