gas cap, idle, A/C

[roverman]

This is going to be tough to describe because the problem and the symptoms come and go and don't make sense.

Went on a 1000 mile trip over the past few days. Day 1, noticed gas cap was really really tight to undo. Two hands lots of effort to unscrew. Then i stupidly started car before I was finished filling and noticed idle was going back and forth between 400 and 800 rpm, up and down every few seconds. It ran fine other than the strange idle, which would come and then be normal and then do it again etc...

The next day I noticed the A/C stopped working. Stopped at auto parts store and borrowed a gauge that said the refrigerant system pressure was fine. Then the idle and the A/C started working fine. Then it idled oddly and the A/C kept working. The next few days the A/C kept working fine, but the idle problem came and went. Also don't know how or why it would be related but on some fill ups the gas cap was fine and others it was super tight.

Other than all this the truck ran great and i ran 20mpg for the whole trip.

Ideas or experiences?

I can't help but think they are related, but can't figure out how.

 

[bbyer]

Buy a new gas cap?

I find that with my 3, rarely is there just one problem to be solved but that is how to start. I would just purchase a brand new LR gas cap or purchase a Stant locking one, Stant part number 10521, as they do make one, or non locking, 10851.

I doubt the gas cap is the problem, but a new one does not cost too much. It just seems to me that the internal relief valve within the cap is not working and also the LR vapor management pressure release system that is supposed to normally do the task is not working either. The fuel cap vent is a secondary backup system. It could be that somehow the AC senses something is wrong and operation of such is inhibited.

http://www.stant.com/Parts-Locator/

http://www.stant.com/modules/partLocator/view_diagram.cfm?id=10851

http://www.stant.com/modules/partLocator/view_diagram.cfm?id=10521

 

[Disco Mike]

How about fault codes, you must have some, what are the fault code numbers?

 

[roverman]

bbyer: you're right, I'll probably get a new gas cap, whether it's contributing to the problem or not. But it seems the idle problem happens whether the cap is super tight or normal.

Mike, no idiot lights but I don't have a code reader so can't tell you if or what codes it's throwing.

Fortunately the AC has at least been working for the last day and a half through this heatwave we're suffering through.