I cleand iacv and all the radiator hoses. Car still idles rough. When I turn on the headlights it runs great. I have no problem driving with the headlights on, but wondering what could be the problem. Had the timing belt changed recently. Maybe the "mechanic" screwed something up. Any ideas?

 

What is the idle speed without the headlights on? When you turn the lights on, does the idle speed increase (there is an electrical load sensor that feeds the ECM as an input to idle speed)? How are the plugs, wires, cap, rotor? Does it idle rough in Park or Neutral, or just when in gear?

 

Idle speed without headlights on bounces between 600-700rpm. With lights on it stabilizes at 700. Idles fine in Park and Neutral at 700rpm. Only have issue when in DRIVE lights off. I'm going to replace plugs and wires this week.
Thanks for your help.

90 EX 198,000(original owner)