I’ve got a 1990 Toyota Tacoma SR5 with a 22RE engine, 5 speed manual transmission.
it starts just fine but when it gets warm and you put your foot on the brake the engine revs up and down. Take your foot off the brake and it idles normal. I’ve check for a vacuum leak and can’t find one anywhere, I’ve replaced the brake booster, throttle position sensor, throttle set screw. I really don’t know what to check next.
Only a vacuum leak would produce the symptoms you describe. Somewhere between the intake manifold vacuum take off and the power break booster, there is a leak.
Some youtube videos suggest that it's an IAT or TB issue. It's a little difficult to troubleshoot/diagnose without "shotgunning" the problem (replacing parts until you solve the problem). I have an intermittent surge at idle issue after cleaning both the TB and IAT. My TB sensor is showing the throttle open at 20% at idle even though the valve is closed at idle so I'm going to start by replacing that sensor first since it is the cheapest and, if necessary, the IAT and then the TB. I've already checked for vacuum leaks. That surge is of major concern so keep your foot on the brake or you may end up rear-ending someone.
@theeel - what vehicle are you talking about? The original question was about a 1990 22RE. What's yours and shouldn't it be a separate question?