My 1997 Ram 3500, with the 5.9l cummins, runs rough, or dies at idle when the air conditioning is on. Runs great at highway speeds, and even off idle. Any thoughts?

 

turn off the a/c

 

Cowgirl,

I used to have a 97 and about once a year I had to bump the idle up a little bit. Your idle you be about 800 RPM in neutral on an automatic, or 750 with a manual.

To adjust the RPM, look at the throttle linkage on the left sde of the engine toward the rear. You have to get on top of the engine and look down. With the engine off, move the throttle linkage and you will eventually see the stop nut. If I remember correctly, you need two 10mm wrenches. One for the lock nut and one for the top nut. Just extend the stop nut a bit to increase the idle RPM. Since its hard to hold the throttle open while making the adjustment, I would take some wire and wire the throttle to the full open position to get at the stop nut more easily. Just make sure you release it before starting the engine or you will think you adust the stop nut out way too far.

 

I'd check your fuel filter as well. I dont know how often you replace it, but maybe time. Also, its pretty easy to pick up a crappy tank of fuel and plug a filter up in no time.