Ok, adjusted TPS, dinked around w/ idle mix screw, no vacuum leaks. Here is what happens:cold start the car, usual rev to 3000 for 30 seconds/or I put it in gear. Holds idle at 1500 till she is warmed up. Then idle drops to 1000. I press the brake in, idle drops to 400 RPM. At night, w/ headlights on, I press the brake and the idle drops to 200 ! So what is the problem? If I turn on thr a/c, idles perfect at 750, even w/ brake in and lights on! I am so confused! Bad ground? Weak alternator? The battery gauge reads 12+ volts. 1991 N/A.

 

Maybe your booster is suckin a tad bit toooo much off your engine? I had that problem on my truck, i hit the brake and my truck just bites the dust, turned out I had a blown booster

 

Booster? What be that?

 

the big drum round thing behind your master cylinder.

 

Hmmmm. What does it do? I have never heard of it before!

 

its what makes it easy to push your brake in when you start the car. Notice how your brake is stiff as hell when the car is off, but gets easier to push when its on? Well thats the cause of it!

 

Oh. I was thinking some sort of electrical bug, seeing as it only happens when the brake lights come on. Also, it is worse the more of a pull I put on the electrical system. If I turn on my headlights, my stereo, and open a door so all the interior lights come on, and push the brake in, it will almost die. Unless it is still cold, then she idles like a champ, or if the a/c is on (thank you BAC!). If it was the booster, wouldn't it do this no matter what electrical systems/ac were running?

 

Well you never said *ALL* of that! So hit the brake, and push the switch in with your hand, that should solve it, if it still idles, bad alt perhaps.

er, maybe you did, ok I'm blind!

 

I think I will just try to reground my electrical system again, but this time I will not fry any more grounds!

 

well, if you start your car on fire, I got dibs on the engine!

 

Very funny! Last time I tried this, I charged the chassis, and fried the ground from the back of the engine to the firewall, you know, the one that is the ground for the spark plugs! My car was down for 2 weeks, untill I finally figured out what I had done!

 

does that mean I should have high hopes? Anyway, good luck with your problem, I have to try to fix my 20+ broken bolts from taking off my bumper, god damn rust!