2002 Dodge Intrepid

Weird prob with this car. It starts ok but usually (90-95% of time) runs rough when I reduce pressure on the accelerator. During this time, the cruise control will not work; the cruise light doesn’t even come on. However, about 5-10% of the time the car runs fine and the cruise control works. Not sure how these two are related. Help!

Is the Check Engine Light on?

How many miles on this Intrepid?

What’s its maintenance history?

Have you taken the car to a mechanic for this problem?

Yes, took it to the mechanic and replaced the O2 sensor. 145000 miles, maintenance is good for the last $50,000 miles whioh is when we got it. No other major problems. Thinking of replacing the MAP sensor next, and a Dodge mechanic also suggested it could be a simple brake relay switch which is misfiring, leading to both the cruise not working and the car running poorly. this seems a bit of a stretch to me, but it is a cheap thing to fix so I am going to try this too.

It sounds like you may have a bad vacuum leak somewhere. Possibly in one of the lines leading from a solenoid that controls part of your emission control system, or maybe the one that goes to the cruise control actuator. I would visually inspect all the vacuum lines for a leak. The MAP sensor works off engine vacuum too, so if you’re getting a code related to this, it may still be a vacuum leak. I don’t see how a “brake relay switch” would make the car run poorly.

If the check engine light is lit, what codes are coming up?

If this engine has an EGR valve, it could be stuck open causing low vacuum.

Throwing parts at it without determining if it is really a problem is going to get expensive quickly. If the CEL is or was on, why not share the codes with us? We can give further insight with the codes.