Questions and Answers
Racing Wagoneer
Q. I own an 1989 Jeep Wagoneer with a fuel injected 4.0 liter and an automatic transmission. Sometimes, when I come to a stop or I am idling in park, the engine will rev up to 1,500-2,100 rpm's on its own. I've seen this happen with other vehicles when the choke is sticking and a quick jab on the gas pedal usually solves the problem.
This is not the case here, sometimes the quick jab just gets the rpm's stuck at a higher number. So far I've just been turning the motor off for thirty seconds or so and then starting it up again. In most cases this temporarily solves the problem. Any information you could give me that would help me solve this dilemma would be greatly appreciated.
Thanks,
MattA. This engine uses a stepper motor to control the idle air flow and thus the idle speed. It is possible that the stepper motor is bad and not able to control the idle speed. The other possibility is that the passages are clogged with gum and varnish. I would try pulling out the stepper motor and air intake hose off the intake manifold and giving it a good cleaning with carburetor cleaner. This could very well fix the problem.
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