Sulli8888

Sorry, I posted this under newer models my mistake so I re-posted it here correctly.
My 1991 5.0 / 302 does not idle up at all when starting in mornings. It idles about 500 rpm in park, when warm about 650 in park.
My other vehicle idles up around 1000 for a min or so then idles down. I have cleaned the IAC ( hope i used the correct initials ) it looks good as far as i know.

Sulli8888

Does anyone know what sensor or what makes the 5.0 idle up when first starting? Mine just idles at 500 or 600 at start. I think it should be higher for a few mins then idle down?????

Tinman98

Yes, it should idle faster. The Idle Control Solenoid (ICS) goes by a number of names, the factory manuals call it the Air Bypass Valve (took me forever to find it). I have a similar problem with my 1988 351, but I don't know if the two vehicles have similar fuel control architects. I was sure my problem was the ICS, but after replacing it, it wasn't. With the computer controlled engines nowadays, there are so many things to check. Does the Engine Check light come on? Reading out the code can give you a clue to where to start. That's my next step. I have the Emissions Diagnostic manual so that should be a big help. I am finding out that there is usually no quick fix and the diagnostic procedures have to be gone through step by step until the solution is found. Many people have just started replacing parts to no avail (myself included) and most of the time it just doesn't work unless they happened to get lucky. There is just no substitute for methodical testing by using the factory's logic steps. Hope you find it before it gets too frustrating.


Milo