Hi Rev in N and P

[racephan6]

I have a 1992 4WD Explorer with 4ALD automatic transmission. It sat for 6 months. When I recently started it, it began to run ok. I took for a short drive to make sure everything was ok and I noticed a grinding sound. When I got back and put it in P, the engine revved up to 3500RPM and stayed there. When I switched back to R, OD, D, 1, or 2, the RPM returned to 1500RPM. N also caused the RPM to raise to 3500PM. I shut off the engine and looked under the car and I had alot of leakage from the rear end housing cover plate. The transmission fluid level is ok. Is this Park/Neutral sensing switch problem or a vacuum diaphragm problem or something else? After sitting for 6 months, the engine is running fine, it is a transmission/driveline problem. Any suggestions.

 

[Billy177]

i would try cleaning your maf and iac also i would go to the gas station to fill the tank up to dilute the old gas and run some injector cleaner through it

 

[V8BoatBuilder]

Check your throttle cable and throttle plate. I would think the throttle would need to be open a good way to let enough air in for the engine to reach 3500 rpm.

Also, fluid leaks can mean the death of a component, find it, fix it, before you drive it.

 

[Billy177]

checl your motor mounts also

 

[Rhett]

Check under the hood to make sure all the vacuum lines are intact. Mice or rats could have gotten in there while the truck sat for 6 months and eaten the vac lines, or the lines could have fallen off or become cracked from age. Also check for vac leaks on intake stream (air filter, air tube, throttle body sealing, upper intake manifold).

Make sure the throttle cable is properly lubed and make sure the throttle body itself is opening and closing properly. If your TB is set a little open it can really set your idle poorly, especially in Park or Neutral. Also make sure the Throttle Position Sensor (TPS) is functioning properly.

If you've got leaks on the rear diff, I suggest you get a new rear diff gasket, unbolt the diff cover, clean it all, install new gasket, progressively torque the bolts when putting the cover back on. Then refill the diff with gear lube thru the fill bolt. If you don't the whole rear end might go on ya, and that's expensive vs. a cheap gasket and some gear lube.