hello, I have a 1991 ford ranger 2wd. It has a 4.0 v-6 engine. The problem I am having with it is it hesitates when you take off and stalls at times. It also the idle goes up and down when it is just sitting in park or at a light. The check engine light will come on while driving it.,but goes back off when you restart it. We just replaced the fuel filter and plug and wires. but don't know what to do next. PLEASE HELP.........

Start by cleaning the Idle Air Control motor. hold it with the electric motor pointing up when you spray it out with carb clean and scrub it with a tooth brush...disconnect the battery for a few and try that. also clean the throttle body with a toothbrush and carb clean and wipe it dry.

people will tell you to not clean the throttle body because it has a coating on it, if there is carbon, the coating is already compromised.