1986 928 erratic idle and performance, what are some things things to check?

This must be a k jetronic fuel injection system, if it is clean the plate with a carburetor/injector cleaner also clean the idle valve and throttle plate. Check everything regarding maintenance spark plugs, cables, rotor, filters etc and test the car. Generally this system has this issue

Hello Hector, The car has teh LH system with the MAF, is this what I need to clean? I removed the air filter and some leaves from the MAF screen. You say to spray that intake with carb cleaner? I will check the plugs and wires too. Where is the idle valve located, and the throttle plate? Thanks for your advice. Tony

Ok, not spray, clean the parts with carb cleaner. the throttle is the plate located in the intake it gets dirty with sludge, the idle valve if equipped is a cylinder generally black or gray, it lets air bypass the throttle plate it should be near by also. if the maf is the plate type check that the plate moves freely and it is clean, you can clean it with carb cleaner. check everything that has to do with maintenance the spark, cables and fuel filter also.

The spark plugs and ignition wires are probably the exact cause for your problem. After the engine warms up any defect in the ignition wires or spark plug connector will start arcing.