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Mustang 1994 5.0 litre troubles idling, new to forum


Just bought 1994 mustang 5.0 litre and it idles really rough and cant seem to find the problem, things that have been done before I bought it. Just dont know where to look, what dont make sense and you might think Im nuts but when I turn my heater on it idles up to 2000 rpm. I just cant get it to smoth out, I adjusted disrutor and changed out cap and rotor and not change. Any help would be great :o

-3037 aluminum heads
-M-6250-X303 cam
- Scorpion roller rockers
-2.5 inch duel mandral exhaust
-super flow 40 mufflers

Old topic but what the heck.

The first thing you should check it the mass Airflow sensor, idle air control, and PCV valve.

Mass airflow sensor
It's all pretty easy. Pull off the mass airflow sensor and disconnect it from the wiring harness. You want to be careful with it. At the bottom there will be wires. Don't touch them, just put it on a table then spray the wires with mass air flow cleaner. Don't use other stuff. It'll dry in about 20minutes, come back spray it again, then once it's dry put it back together. Remember, other than the spraying don't be touching or messing with those wires because they are delicate and you'll be out about $170 if you break it.
You might as well check the other easy possible issues that could cause this.

idle air control
Pull the IAC valve out and clean the inside of it with throttle body cleaner, put it back on.

PCV valve
Pull that off. You will probably have to use a soft brush(wifes' toothbrush, haha), once all of that black junk is all gone. It's done. You may just want to replace it though because they are not that expensive. Maybe $18 or something like that.

After you've handled that do a test and start the car. I'm pretty sure it'll be fixed. If not then I am truly sorry and you can start getting mad.

It could be a vacuum leak, EGR valve, throttle position switch, or even the coil Packs.


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