Hi everyone, here's the newest fun thing my XJ is doing.

A few days ago we had a huge rain storm (like epic proportions), and I had to drive home through it for about 40 miles. The next day I was getting a rough idle, then it would clear up for about 20 to 30 seconds, then it would stutter again.
When driving, it doesn't stall, but somethimes at a light it will konk out, sometimes not.

While driving, it felt like there was a stuck caliper, or a sticky brake. They are all fine.

Checked the trans fluid, it's at the right level, and doesn't look like water got in there.

Engine oil looks good, no foam.

I went through the engine bay today and put dielectric grease in every connector I could reach/see/find. Didn't help, but couldn't hurt!

TPS seems to be working, I adjusted it one way and the other with no difference - BUT I did not test it with a multimeter, not sure how to.

I have a video of it running and stuttering, but can't seem to get it to upload off of my phone. I will post a vid when I can

1989 XJ 4.0 I6
I should also mention that I am still getting nearly 20mpg, weird? Something bad, something easy?

 

It's your 02 sensor, or it's wires. In this unfortunately sabotaged thread, I explain that my 20 sec. or so idle fluctuation cleared up after the new 02 sensor.
https://www.cherokeeforum.com/f2/ren...ce-rms-133153/

From post #4> "The idle seems even now. Was cycling every 30 seconds. Rpm & Vacuum would drop, then a little surge, even out, repeat. Besides the 02 sensor, what I measured was 1/10 of an ohm improvement at the dipstick ground. That's all that was touched.

Do check your wires Per EcoMikes instructions on-top in the link. Less than an ohm to ground, 5v or so from the ECU, and 12 or so to the heater wire.

If you like you can back probe the 5v feed and look for the needle bobbing on a cheap analogue meter around 2-1/2 V @ 2,500 Rpm. For this the impedance of the cheap meter might not matter much.

JUST REREAD YOUR POST.....MMMM...MIGHT BE THE 02 SENSOR IF THE IDLE STEADILY FLUCTUATES...

Ont-op in my sig is Cruisers tips. The adjustment procedure for the TPS in in there somewhere.

 

So it turned out to be the O2 sensor, but not the sensor itself. Because I had to drive through the storm, I decided to go after my Jeep with a wire brush and some dielectric grease. I started from the top down, pulling every connection I could find apart, cleaning them, and then using the dielectric grease on them. Well, yesterday I got under the Jeep to check the O2 sensor, and figured that while I was under there, to bring the brush and grease. Found three other connections, and did those, and when I got to the O2 sensor, the connector wasn't too bad, but figured I'd clean it and grease it before I went and dropped $70 on a new sensor. Cleared it right up.

Long story short - Cleaned and put some dielectric grease in the O2 sensor connector, and it cleared up my engine stumble.

 

Supper! Well done. Btw...I have nothing against dielectric grease, personally I think it works fine. That said, it's not a conductor, so some recommend against it. There is a product, Oxyguard. It's a conducting grease. With that I suppose a guy would need to be supper careful to not end up shorting things with it. Happy trails!

 

Yeah, with all the connectors under the hood with multiple prongs, one would have to watch which side they put the Oxyguard in, but otherwise I have had success with it. Most of the time I just use dielectric grease when I know it's going to see a lot of water. (plus it's cheap)