So I was having some idle issues again (after about 2 years of no idle problems) with my 1990 Montero. I figured I'd try the solution on the Solving the 3.0I V6 Idle Problem page. I removed my throttle body, gave it a good cleaning, and put it back on (with a new throttle body gasket) and fired it back up. The problem didn't go away, but the cleaning sure made it more consistent. Before, it idled high (around 2k RPMs) until it warmed up, then it would either stay idling high or start bouncing rhythmically between 1300 and 2200 RPMs. Now it starts doing the idle bounce before it is fully warmed up, and is more precise in both the RPM levels and the rhythm. The engine runs fine when driving, but sure doesn't like to idle quietly.

When the engine is warm, and I disconnect the MAP (Volume Air Flow?) sensor, then it goes into a closed loop and idles fairly normally and the CEL comes on. But I don't get any CEL light when it's doing the idle bounce.

Could I have introduced or exacerbated a vacuum leak when I "fixed" the throttle body? Is a vacuum leak or extra air intake the cause of the 3.0I V6 Idle problem? Could it be my IAC? I took it and the TPS off when I cleaned the Throttle body. What other problem could mimic the dirty throttle body problem? I'm kind of stumped as to what my next step should be in trying to diagnose this issue. Any insight is appreciated.

Alex.