I have a question about something I've noticed at cold idle.

This is a 91 vert n/a with no mods.

When I start the engine when it is like above 50 degrees or so outside the RPM's fly up to around 3000 for about 15 seconds like it is supposed to and then drops down to around 1800-2000 and slowly drops to 750 as it gets to normal operating temp.

When it is colder, like 30 degrees or lower outside, it only initially jumps up to about 1800 RPM, hangs there and runs kinda rough for about 30 seconds or so, and then something kicks in, the idle smooths out and jumps up to about 2200 RPM and slowly comes back down to 750 from there.

What is this "something" that kicks in to smooth the idle out? Does it have something to do with that Air Bypass Valve? What the hell is that thing's purpose anyway? I thought when I read something about the ABV before, it had full power to it right at startup to make the idle scream at 3000 for about 17 seconds and then the ECU cut power to it to make the idle drop back down. Is this the case?

I'm positive that it is not something with the TPS or the BAC. I have tested the BAC and it checked out OK, and I spent about 10 hours (total PITA) last summer getting the TPS adjusted to exactly where it needed to be.

Anybody got any ideas for me to try?

 

OOPS......It is actually called the Air Bypass Selenoid Valve and not Air Bypass Valve. It is underneath the upper intake on the driver's side towards the rear.

 

Thermowax. It is a little ball of wax that drips on something or another and causes the idle to drop. At least that is how I have had it explained to me! I could be wrong!