Engine is a 2.5 liter four, trans is a five speed (four plus an overdrive) NP2500.
I'm still trying to figure out why the following is happening and having no luck. This is what's happening:
I park the rig facing three blocks of downhill. I always warm the truck up when I start it up and once it is warmed enough, I put it in neutral and take off the brake. It starts coasting downhill and I don't have my foot on the accelerator. Almost immediately, the motor rpm goes up to about 2000 rpm on its own. When I reach the stop sign, I come to a complete stop at which point the motor just as suddenly drops back to a normal idle.
The motor will race like this whether or not I'm coasting forward or backing up.
Candidates for the problem at this point are:
- a stuck throttle cable (I've verified that it isn't though)
- broken motor mount (I looked and it's not)
- SMEC (Single Module Engine Controller) is causing the AIS (Automatic Idle Speed motor) to act weird for some reason. This can be caused by a bad: a. throttle position sensor b. oxygen sensor (doubtful) c. ? d. bad SMEC
Any other ideas? This one even throws the guy at the dealership's service department.
TIA.