Hello everyone,

This is my first thread here and I hope you are able to help me. I have a '92 XJ 4.0 manual with vacuum issues. The idle seems to be rough or looping and I've been trying to fix the problem, without the result I was hoping for. My RPM indicator says that the idle is around 1100. But also tends to misread from time to time. When applying the brake it seems to fluctuate and go up.

What I've done so far:
- TPS replaced;
- Throttle housing cleaned and new gasket installed;
- IAC replaced;
- Intake/outlet manifold gasket replaced;
- Vacuum lines replaced on intake manifold to MAP sensor, valve cover and fuelrail;
- Brake booster replaced except of the vacuumline.

As I said, so far no dice. The computer doesn't give a error. But after I replaced the gasket on the intake/outlet all seemed to be fine. But after a while the idle went up again and doesn't want to come down and stay stable.

The next thing for me to do would be to visit an expert mechanic, including all costs. So I hope you can give me some advice on how to proceed.

Thanks in advance!

 

I think your model has an EGR valve and it's probably stuck open or at least leaking and needs replacing. Just my thoughts. You can try taking it off and cleaning the pindle and seat.

 

Thank you for your comment. I haven't heard of this one before! I'll look it up and try it out. Can you tell me where it's located and can I just clean it with brake parts cleaner and a rag?

 

I'm not saying it does, but it may have one. I know the early Renix jeeps did. It's vacuum controlled and bleeds exhaust back into the intake to reduce emissions. I just thought about it because your problem is common on engines that do have an EGR valve.

Okay, I just checked Rockauto for your 92 and they have an EGR gasket so I guess yours does.
Farther checking shows no EGR valve after 90. Oh well.....

 

​​​​​I understand what you mean and all the advice is welcome! I looked it up yesterday as well, got the same results. It shows gaskets, but not the actual EGR. I tried looking up some photos of the EGR and it's location. I'll also read the factory service manual today, maybe there is something in there. Thanks!

 

No EGR after Renix.

Spray carb cleaner around suspected areas at idle. You'll know if you hit a vacuum leak.