Sometimes my 1991 GMC pickup runs at a higher idle than normal. I have replaced the plugs,wire,rotar,and cap. What should I try next.

Do you still have this vehicle and if so did you ever find out the problem? I am curious because my truck started doing similar things and then stopped running altogether. We have replaced my throttle body (with another used) as well as the map sensor, checked wiring, spark plugs, wires, rotar and cap. Still the issue continues.

If not wrong this engines also need a valve lash adjustment time to time even do this littl eng. 22RE runs rough normally, try it wont hurt.

You might try replacing the valves that probably got bent when the engine was started with the cam timing being off.

Check/replace/clean the IAC valve(idle air control valve). If ok, check for vacuum leaks or clogged vacuum lines.

check timing ?

I suspect what you have is a vacuum leak.

1. Try hunting down the leak with carb spray. Don't get too crazy with it, when you get to your leak it will change the way it runs. Also do not deliberatly spray this on spark plug wires as one stray spark and you will need a fire extinguisher. This method is safe, just use your head.

2. If you detect a leak at the brake booster, unplug the vacuum source line for it and plug it. Then trying running the truck again. If it runs normal the leak is in your booster and must be replaced.

try advancing the timing a bit that mite help

replace the timing gear its wore out

OR MAYBE YOUR GAS FILTER LOCATED UNDER YOUR OIL FILTER, PANEL UNBOLTS UNDER RIGHT FENDER WELD FOR EASY ACCESS, THE BIGGEST FIX FOR ME WAS TO TAKE OFF THE ADVANCE AUTO BRAND NEW SPARK PLUG WIRES AND INSTALL NAPA WIRES, DISTRIBUTER, ROTAR BUTTON, AND NGK ORIGINAL SPARK PLUGS. ROB

Check for antifreeze leak, make white smoke under hood, and check your antifreeze level