Lexus082

If the idle air control valve was bad on an sc400 and was causing a rough idle, wouldn't pressing on the gas pedal temporarily alleviate the rough idle and the engine would run smoother instead of shaking?

MooJohn

Yes, so if yours still shakes the problem is somewhere else.

Judging by the number of threads you have going, maybe you should have a (competent) professional look at your car. It might just have too much wrong with it to have strangers diagnose it by just written descriptions of the problems.

Lexus082

For the last few weeks, the car had stalled out approx 10 minutes from a cold start. It will restart by will stall out within one second from restarting. If you leave the engine off and let it sit for about ten minutes it will run for a couple minutes before it stalls again. One day I let the engine idle for over 30 minutes and it didn't stall. So I was convinced the car had to be driven in order for it to stall out.

However, a few days passed and I started the car up and it was misfiring and running slightly rough at idle and for some reason (can't remember why) I decided to pump the brakes to see if I could get it to stall and sue enough after I pumped the brakes about 3-4 times it did stall out, I'm not sure if it was a coincidence or not. But now looking back I think that did cause the engine to stall. So I think I its possible the brake booster is leaking air causing a vacuum leak. I've looked over all the vacuum lines several times and came up empty handed. So my plan is to disconnect the vacuum line that goes to the brake booster and plug the other end coming off the intake manifold.

Lexus082

Due to limited amount of time I have to work on the car, I decided to remove alot of the parts I had recently installed to try and eliminate the misfire. So after removing the plugs, distributor caps and rotors, ignition coils and EFI relay and swapping them out for the original parts that were on the car, the misfire has now been corrected. I have a feeling its one of the ignition coils, but the resistance values on both coils tested good. I'm just going to reinstall each part one at a time and single out which part(s) are causing the misfire. Then I can get back to my original problem with the engine randomly stalling out.