I just picked up a '97 1500 reg cab short box, 3.9 auto 2wd. When cruising normally, everthing works, but as soon as I hit a hill or put the engine under load, the fan changes itself to windshield defrost, then back again once I'm back to cruising. The cruise controll doesn't work as well. I know the plenum is leaking, will that cause vacuum issues?

 

Plenum is a big one.

Bad check valve, or, its absence.... in the vacuum lines leading inside usually will fix wild vents.

If the cruise light comes on, but, it still doesn't work, check the vacuum line from the cruise servo (under the battery) to either the throttle body, or, one of the fittings on the passenger side center of the intake.

 

Where is the check valve, and how can I check it? The light doesn't come on for the cruise. All fuses are good, except one marked buzzer, it's been pulled out because the buzzer won't shut off. Very irritating. On a seperate note, does the keg mod make any noticable difference on the 3.9? I figure I'm going to have it all apart anyways might as well do it if it's a good idea.

 

use the search tool at the top of the forum and search for "Wild Vents" there is a 10+ page thread on this issue.

 

Thanks alot guys! I'll check into all that today.

 

Ok, there are two check valves on the passenger side of the manifold, one good and one bad. I couldn't find any damaged lines. But I have to wait for a valve since neither of the shops here carry them. Any thoughts on the keg mod for a 3.9?

 

Not sure..... the kegger mod will move your power band up a couple hundred RPM.... Don't know how well that go over on the six.....