I cant seem to pin point my issue. Any help would be appreciated.

I am having an issue with my heater.
If my Jeep is at idle, everything works as designed. While under throttle, If I have the control switch in the "Heat" position it will switch to defrost. Close the throttle and all goes back to normal.

Do I have a vaccum leak, a line connected wrong, or a bad component?

Thank you!

1993 XJ 4.0 AW4

 

Vacuum leak.

 

I havent been able to find one under the hood. Where do I start?

 

Start at the vacuum ball ubder the front bumper passenger side. Check it for cracks and loose hose connections. Fallow all the hoses to the fire wall.

 

Will do. The ball has been relocated by the PO. I will report back with my findings. Thank you

 

I think I have the same problem on my 85, I even hear a squeaking in the heater box area when going from open throttle to closed throttle with it in the Off position. Would mine start at the tin cans on the inner fender as I don't think I have the ball under the bumper?

 

Not a problem. Good Luck!

 

So I found two bad lines. I fixed them but still have the same issues. Does anyone have a diagram?

 

Do you still have the crappy heater control valve on the heater hose going to the heater core? That is also vacuum controlled. If so check out the vacuum line to it or you van remove it all together and plug the vacuum line to it. I do know that your problem is vacuum related. Make sure to check out every vacuum line in the engine compartment. I'm not sure but I think that you also have some vac lines under the dash to the hvac controls.

 

The PO is a total hack. Thats the reason I am doubting his work as far as the routing goes. I will dig a little farther. ..

 

Here:

 

I think my vacum ball is different then the one pictured. Mine has 2 ports on each end.

 

Don't matter. Get on to checking out the lines.