1989 XJ 4.0 4x4 Auto 131,000 miles Stock

My XJ is stumbling at idle and when driving sometimes. Other times it idles fine. It's sort of random. I can feel it wanting to cut off at idle and the battery hand will even dip a little and back up, sometimes. On the road the battery hand doesn't move but I'm giving it gas.

My checklist of things to check or do is:
1. Have battery load tested. I read it can have good cranking amps but then struggle with a running vehicle.
2. Clean IAC and throttle body (is carb cleaner ok or not?)
3. Clean my grounds.
4. Check CPS
5. Replace spark plugs. It's not been long but my Valve Cover is leaking oil (future fix) and maybe it's possible that rear plug has oil on it and fouled.

I think that is the quickest and hopefully most likely causes. Any others to add to the list? And of those, based on my symptoms, which do you guess is the cause for fun?

 

If you have a multimeter check the battery while it’s at idle. Should be around 14-14.2~

have you changed fuel filter, checked air cleaner?

i would definitely clean the tb and you can use carb cleaner.

You can also pull a plug and look at it or a wire and see if the miss gets worse or stays the same.

 

Solved: Wanted to come back and just let anyone know that this is now fixed.

First thing I did was check the alternator and load tested the batter.

(How to load test for those future unfamiliar readers: set a multimeter to DC voltage. Jeep off. Put the red lead on the positive batter cable and the black on negative. Now set the multimeter in the window where you can see it and crank the jeep. Voltage should not drop below like 9.6 or so. Mine was 10.2)

So then I cleaned the IAC sensor and hole by just simply spraying it with cleaner. Wanted to be gentle as I know they can get messed up. I also cleaned my throttle body.

And it has not stumbled at idle or om the highway once and I've drove it 5+ times. Didn't realize the IAC could cause stumble while driving like it was doing.

Hope this helps anybody else that is unsure. Just go ahead aad clean the IAC no matter what.

 

Nice job!! It's amazing what some maintenance can do.

There was never a factory interval or procedure for cleaning the throttle body. every tune-up at 30,000 mile intervals worked for us.

 

Probably more the TB than the IAC

Now onto the rest of the preventative maintenance!

 

Update: It came back and then went away again for months. And now it's back again. This has been going on off an on for years. I really want to fix it this time because it is pretty bad this time. Proabably the worse ever. I cleaned the Throttle Bofy and IAC and it made no difference. I never really thought that was the cause because of how intermittent it is.

I also tested the engine (3 wore connector) of the TPS and the readings were slightly off so I rotated it and tightened it back down. It made no difference. I have not tested the other TPS (trans) connector.

Here is a video of what it is doing. Sometimes when I crank it up it will automatically have the issue. Sometimes it won't. I am sitting still with my foot on the brake and clicking through P, R, N, D. As you can see it will be idling fine and when I click to another gear it stumbles and then picks back up and idles fine again. Sometimes it will stumble worse and sometimes not as bad. (I also swear that sometimes me pressing the brake harder causes it to act worse but that could be my mind playing tricks). Sometimes when driving and I slow way down to make a turn it will even stumble and cut off. I also sometimes think I feel it acting up while driving at speeds but it typically runs pretty good while driving so again maybe it's my mind so cued in that I'm noticing something not there(?).

What else should I test/check to rule out? I don't see how it could be the fuel filter as somebody suggested earlier because how would it clog then get less clogged then more clogged? It has been so intermittent and that is one of the reasons I haven't fixed it yet. As always I appreciate any help.

I will also continue to read and test but might as well update this thread and ask for help while I do.

Edit: Had video uploading issues. Will try again later.

 

Have you added a ground from the negative battery terminal to the body?

added a cable from firewall to intake manifold?

 

@cruiser54

No, I do not have those extra grounds. What's weird is I thought I remembered doing them (because of your tips) but I just went and checked and I never actually did them. The only thing I had done was scrape the paint on the cable ground at the firewall. I did that years ago. I guess I forgot to finish.

It's also been a while since I cleaned my grounds anyway. I guess I will clean them and add the extra grounds (finally) so any ground issues can be ruled out.

 

That firewall ground can be messed up at the head. That's why I advocate ADDING the cable to the intake manifold area. It's covered in the Tips.

And yes, double check the grounds at the dipstick stud.

 

I cleaned my grounds and added those two extra grounds and it seems to have solved the problem. I have driven it everyday since last Friday and the issue has not happened yet.

 

Well, imagine that!!!!!

thanks for the update.