1994 6cyl (3VZE) 4wd
After reading the marvelous success stories by those who have carefully examined their Throttle Position Sensors, I decided to do the same, with the help of the FSM (Factory Service Manual). Now I am much more confused ...
I think I need to know what the dashpot is
supposed to do.
Here are the clues:
1. The truck runs perfectly (which may be enough to just stop right here).
2. The TPS IDL-E2 reads infinity at throttle closed (should read less than 2.3k ohms). (I'm only 80% sure on this test; the connector is very hard to reach)
3. When running, the throttle opener (at the top of the photo) correctly retracts about 5mm, but the throttle does not follow it. The throttle is sitting on the throttle stop screw (not visible in this photo). Idle is dead-on at 800rpm. When vacuum is removed from the throttle opener while engine at 2000rpm, the idle will drop to 800 rpm when throttle released (should be 900-1800rpm, so the throttle opener is not "opening" the throttle).
4. The dashpot (bottom of photo) is fully extended with throttle closed, but does not extend farther when the throttle is opened.
Should it? Therefore, the dashpot does not hold the throttle open for the one second it should take to gently close. The dashpot does not want to compress further (with finger pressure) either.
5. When the "special service tool" (paperclip) shorts the TE1 to E1 points on the diagnostic connector to set the timing, the idle speed does NOT change when the tool is removed.
Should it? Could this be a hint that the truck doesn't "think" it is at idle because of a bad TPS setting?
6. The Air Valve (idle adjustment) has very little effect on idle speed.
My WAG (wild-ass guess) is that long ago the dashpot failed "extended," holding the idle too high. Rather than fix the dashpot, someone carefully reset the dashpot adj screw, or the idle speed, or the TPS, or the throttle stop screw, or all of them.
Your insight will be appreciated.
