The Bouncy / Hunting Idle Issue got me

[unnormal]

I was driving around the other day when I was suddenly struck by the Bouncy / Hunting Idle problem that the MR2 features.

History: I have been driving this 89 SC for about 4 months without any the problem. When I first got the car I found that the idle screw on the TB was completely drilled out by TPO. Arg, but I was able to remove the set screw on the top of the IAC and turn the grey plastic motor part a bit ccw to restrict the air and bring the idle down to 1500. It always idled high (~1500rpm) when warm.

The IAC was working fine, the engine idled up to 2500 when cold and down when warm.

The other day it was driving fine, I was really low on gas, I filled up with 91, and when I started the car the Hunting Idle started. It bounces from around 1500 to 2500 rpm. If I unplug the IAC the idle drops to about 1300, but doesn't idle any higher when cold. I think unplugging the IAC just reduced the air entering the intake, thus dropping the idle and covering up the real problem.

Could I have dislodged an air bubble and need to bleed the coolant?
If air was entering the coolant system (ex bad water pump) would I see coolant leaking on the ground?
Does getting gas have anything to do with this? Bad fuel regulator?
Did the IAC suddenly go bad?
Ideas?

[muffinman]

At this point it definately can't hurt to make sure that there is no air in the cooling system. Probably wouldn't hurt to do a compression test either although it seems your problem is at the intake.GL

[mr2tim]

You may need to follow the procedure from our BGB to set the idle on your SC*. This includes using that idle screw that you fixed. This will give a place to start with dealing with that idle.
Setting the idle to spec is a must.

After looking for the stupid stuff, coolant, snorkel cracks, loose clamps, bad loom, ac idle up etc you may have to run test on the electricals.

Hope this goes well for you.

*PM me for BGB procedure, too many pictures for this Email.