Hello, I have 1990 jeep cherokee wroth 200,000 miles, i recently started have rough/ low idle, but when I give it gas in park it sounds fine. I've changed the fuel filter and it has newer injectors, could it be a miss fire or an electrical short? Any info will help. Thanks. Also no engine code is coming up but I'm not even sure that bulb works...

 

Try this:
http://www.xjtalk.com/showthread.php?t=10844

 

To see if the bulb works just turn the ignition on but don't start it. The CEL light should illuminate regardless if there's a code or not if the ignition is on and the engine isn't running.

 

No CEL on a 90.

Click on the pink link below and do Tips 1,3,4, and 5 before chasing anything else.

Clean your throttle body as suggested by Earl. See Tip 11.

Make sure all your intake manifold bolts are snug and all the vacuum harnesses are in good shape.

Ever put plugs, wires, cap and rotor on it in the last 30,000 miles?

 

My bad, looked over the fact he had a 90 model.