Fast Idle on Startup

[orion]

On my Bronco, 86 302 EFI(w/243000K), AOD, when starting cold the RPM's go to 1500 solid for about a minute and then back down to the 6-700 range solid.

When starting semi warm it 'rolls from about 500 to 1000 for that minute and then settles. Otherwise runs great, a little rich until warm and normal mpg

Is this normal or "common"?

Should I check for stored codes or is there anything special I should do when I tune her up in two weeks. I plan on replacing plugs wires/cap, cleaning IAC and checking/setting timing along with fluid changes.

 

[wwatsonh]

The cold thing is normal. It's the "cold start strategy" that the computer uses to keep the engine running when it's cold. It's like the choke on a carb. The rolling idle when warm isn't normal, but it is common. Try all your tune up stuff, and see what happens. Pulling codes won't hurt, and may give you some idea where to look. Starting with the whole cleaning the IAC routine is probably a good place to start.

Will

 

[orion]

Grassy @ss

 

[snowman74]

That's an affirmative on the Idle Air Control. If your Bronco doesn't start at about 12-1500 and go down to about 700-800, you might need a new IAC. Oxygen sensors or leaks in your emission system may cause your IAC to not work properly in the future. Make sure you check all your hoses and Oxygen sensors before replacing IAC if it goes bad in the future. Just thought I'd throw that tip in. >-