TheMiddleMan

So over the winter months when it was around freezing here, I had a high idle problem. The odd time I would get a low idle to the point that the XJ was shaking, but for the most part it seemed to be much too high. After the weather started to warm up a bit, my idle dropped right off (no more worries of overheating ).

To compensate for the variation in idle speeds, I have been adjusting the screw on the TPS accordingly to get an idle in the "happy" medium range. The question I have on this is, how far out should that screw be when idle is at normal range? Right now I have it unscrewed quite a bit to make up for the low idle I have (I can see fresh screw threads which tells me it hasn't been unscrewed that far before). I also noticed the black plastic "tube" that the screw comes out of is a bit loose, is that normal?

Does an '88 Xj have a temp sensor that could possibly be affecting the idle rate, or is that more of a TPS/CPS issue?

As has been said in many a thread before, I want to try and narrow it down before I start throwing money away unneccessarily.

Thanks in advance for the help!

P.S. I do have a multimeter if that will help me at all in diagnosing the issue.

cruiser54

Has anybody ever messed with the throttle blade adjusting screw on your throttle body?

TheMiddleMan

To be honest, not sure. If it's the screw I was adjusting, then yes.

I could see the head was a bit stripped from pliers previous to me going in there. The one I was adjusting is the screw that's head rests against the throttle blade (when unscrewed it forces higher rev's).

cruiser54

Allen head or Torx? We need to determine this.

TheMiddleMan

Neither.

It looks like a hex-head metric bolt, maybe a 6-32. I have to use either needlenose pliers or a small/thin closed-end wrench to turn it.

cruiser54

Got a pic or a good description of where it is located?

TheMiddleMan

It is dark out, but this should give you an idea of what I'm talking about..in this photo it's the screw right on top of my finger in the pic. TPS is on the left side of the screw...I'm actually pulling back the throttle blade to the right.

And a second one just in case...

TheMiddleMan

I just realized as well, after reading through a few of your posts that you mentioned some of the TPS's are NOT adjustable. Wondering if that could be the case here and I have been shooting myself in the foot by messing with that screw, just a thought.

TheMiddleMan

Sorry to keep answering in my own thread, but another thought came to mind.

With that screw adjustment, I assumed it was adjusted to push the throttle blade into a position that basically forces higher or lower idle/rpm's.

The more that I think about it, is the screw used to adjust solely the TPS, internally in the TPS? I may have been trying to hard to think outside the box with that screw adjustment.

cruiser54

I didn't know you were working on a 4 cylinder. Idle fluctuation is most commonly caused by rotted hoses, I think 4 of them, that are between the throttle body and manifold?