When the cruise light flashes the engine ideals at a lower RPM. Usually not a big deal, but when I’m in reverse the car will often stall out. The flashing light comes and goes without apparent cause.
I would be very surprised if the Check Engine Light wasn’t also lit up.
Is it?
No. I’ve discussed this with a repair shop and a Toyota dealer, neither has heard of this happening. Of course, it won’t happen when I take it in.
It’s very strange that it effects the idle speed. The cruise control device works fine.
Are sure that the CEL is actually working?
See if it turns on–briefly–when you turn on the ignition.
Yes. It does turn on.
If there are no codes stored and the cruise contol works I would start by checking the engine grounds. Many time oddball intermittent electrical problems are caused by poor grounds. If the car has ever been in an accident start with the grounds in that area first. I would also try wiggling the wire harness with the engine running to see if you can make the car act up.
It isn’t at all strange that the cruise control affects the idle speed. It does, after all, control the throttle plate via a throttle plate motor.
If the car runs fine without the cruise control on, you can safely rule out all the other systems and sensors. The CC system should simply activate the throttle plate beyond the point you set the CC at and when the VSS signal tells the ECU that the speed has dropped below the speed you set, and allow it to drop to the position it was at when you “set” the CC. The motor “sets” the idle when you “set” the CC speed. In your case, it sounds like the ECU is allowing the idle to drop all the way down.
You should have stored codes.
So, two questions, does the car run properly when the CC isn’t ON and has anyone checked for stored codes? This may be a chassis code, so you unfortunately may have to visit a dealer.
Oh, and what engine and tranny do you have?
OP said it stalls in reverse. Have you tried cleaning the IAC valve?