Chick-N-Picker

1989 XJ 4.0 4x4 auto 84,xxx miles

I have a new problem after doing the exhaust manifold gasket and everything else I did.

My jeep now idles bad. When I first start it it will idle fine for anywhere from 10 seconds to 30 seconds. Then it will idle down really low and will almost die. Then it will pick back up. It then will idle low and lope again. Repeat. Sometimes though it will sort of even out. If I cut the jeep off and start it right back then the low idle will come right back. And it has died twice.

Quick list of what I did and what's new.
1. New exhaust manifold gasket
2. 746 injectors
3. Cleaned TB & IAC (carb cleaner)
4. New down pipe
5. New flange gasket
6. New vacuum harness
7. Cruiser tip 31

I am currently still running nothing after the down pipe. Never have since day 2. But I never ever had this problem until now. I am so disappointed that I tried fixing stuff and now it caused this.

Lowrange2

I'm not super knowledgeable on the pre-97 stuff but that sure sounds like a vacuum leak or IAC issue.

Hard to pinpoint an issue since you changed so much stuff all at the same time.

Chick-N-Picker

Yeah, I know. Apparently my IAC was fine before.
I've sprayed carb cleaner all around and cannot find any vacuum leaks.

Chick-N-Picker

When I crank it and give it throttle by hand. I can hear what sounds like a little hissing ut I can not pinpoint where it's at. It sound likes it in the EGR area. I know all vacuum lines are hooked up though and doesn't a vacuum leak usually cause high idle? If I unplug a vacuum line, it idles up.

I've sprayed cleaner all around but can not get it to change. So I really don't know what I'm going to do or what the problem is. I can't afford to just buy parts or send it to shop. It's my only vehicle. I didn't see this coming.

Chick-N-Picker

Is there a way to accurately test the IAC sensor. I've looked and I can't find a way. I don't have the money to throw parts at it, unless it's a part that can't be tested, then I understand.

I unplugged the vacuum line going to EGR solenoid at idle (low) and it didn't go any higher or lower. Isn't that what it's supposed to do?

I cleaned my IAC sensor with carb cleaner and a rag when doing all the other stuff. I wasn't exactly gentle with it. I scrubbed pretty good. Could have possibly twisted or pulled it.

I was however gentle with all electrical connectors when unhooking and hooking back up.

I cannot find any vacuum leaks & I've checked 3x with carb cleaner. I've sprayed it all around vacuums and intake/exhaust gasket. The only thing I know could be wrong is that I damaged the IAC. Or possibly one of the 746 injectors is bad. When driving it though it runs fine. They looked almost new.

I cleaned the ground at the dipstick tube earlier this year and besides all of that was fine before doing what I did and was extremely careful (you know I was. I had a 56 post thread), except on the AIC.

I don't see how it could be motor related. It idled fine before. Plus I didn't touch anything to do with that.

I'm going to check my spark plugs tomorrow (less than a year). I'm also thinking of swapping back in old injectors just to see if it goes away. I'm starting to panic and I'm praying someone can help me (again).

I will post a video of it tomorrow.

PS: I'm supposed to get cat, muffler, & tailpipe back on Friday. Finally. So it will get quieter and have correct backpressure

Fsher21

Are there any vacuum connectors on the side of the intake that you forgot to plug? I'm not sure if your year has the same one way check valve in the vacuum line as later years, but that could be backwards. The IAC can be damaged if cleaned too aggressively but I am not sure how to check it, maybe unplug it and see if the problem gets worse.

Chick-N-Picker

What could be backwards on vacuum. Don't know what you mean. I think you had a typo.

Haha no one seems to know about the IAC. I found a page that tells how to check literally every sensor and others stuff. On the IAC. It said "don't know how. If you think it's broke: replace."hahahahaha

Fsher21

I don't know if a check valve can cause your issues, but there should be one in one of your main vacuum lines. Since a check valve is one way only, it would cause problems if backwards.

To diagnose if the IAC is the problem, one from the junkyard should work enough so you don't have to throw money at the problem.