Engine Performance problem
1993 GMC C2500 V8 Four Wheel Drive Automatic 160000 miles
My son's GMC truck is acting very strange. The engine light came on and then went off. It was stalling and now it isn't. The latest thing is that the engine is reving and down by itself. My ex thought it was electrical but can't get an 'codes' to come up. He checked all the wiring. What good this be? Should we take it into a mechanic or is it a simple fix they can do.