Find your Intake Air Temp sensor. It's the sensor just to the rear of the throttle body, has 2 wires, and screws into the intake manifold.

Where it's connector plugs into the harness you will see that one of the wires on the harness side　is brown with a white stripe. Follow the brown with white stripe wire back into the harness. You'll have to open up the split-loom plastic sheathing to follow it. It will come to a splice with 2 other brown with white wires with duct tape over them. They're from the TPS and the CTS. The 3 wires will be　 spliced to a single wire headed toward the C101 connector if you have an 87 or 88. If you have an 89 or 90, you do not have the C101 bulkhead connector.

　

Now go to the MAP sensor. Follow the brown with white wire into the harness from there. You will find a splice with 2 more brown with white wires with duct tape over them. At the splice you will find the 3 wires connected to a single brown with white wire going toward the C101, or just along the firewall towards the engine if you have an 89 or 90. Along with the MAP sensor that you traced, they are the ECU sensor ground port and the diagnostic connector on the passenger inner fender.

　

You now have 2 sets of 3 brown with white wires, one near the firewall and one near the engine.

　

Cut the splices out of each set of wires eliminating not only the crappy factory splices, but also the single wire between them. Bring both sets of 3 wires together. Solder the 2 sets of wires together and insulate them properly with tape or shrink tubing.

　

Zip-tie up your new sensor loom to allow for engine movement.
　I prefer to cover it with some new split-loom or wrap it neatly with electrical tape when done.

　

　

Revised 03-09-12

 

Sounds like a project for next weekend!

 

Time well spent. Go for it.

 

Would a wire nut do the job for a little bit?

 

I don't like those things for automotive use. You'll be able to tell if it's doing the job using your meter.

 

I adjusted the TPS and no change. I'm in vacuum leak mode.

 

Get after it with some carb cleaner. Check the intake manifold bolts for looseness while you're at it.

 

Yep. I put a header on it last spring so, they still loosen up.

 

I GOT IT!!! The set screw on the throttle butterfly was open too far and I tightened up the manifold bolts. I don't think I've ever heard it run so well, minus the knocking.

 

Uncle Bob strikes again. We share in your Joy. Did you readjust the TPS afterwards?


What knocking?

 

I did not, and the ol' 4.0 is pretty rattly. Years of those fram oil filters...

 

Probably very true about the Orange Cans of Death.

Check your TPS adjustment on the "engine" side connector per my instructions.

 

Austin, if you just sit and listen to it idle, does it go even for a bit, start to die, surge a little then even out, then repeat in about 25 seconds? Just curious.

 

Not quite to where it sounds like it's going to die but yeah, a little something like that. I saw your thread where that was the culprit but I can't remember for the life of me what it was that caused it.

 

Ok, I adjusted the TPS and now the idle tops out at 1100rpm, but stayed under 1000 for the most part on my trip through town. I might get a vacuum line kit from the dealership this summer to at least get those freshened up.

DFlinstone, it does not really follow your pattern, but the idle smooths out a bit then drops 100-200rpm and lopes a few times then returns to normal. The whole cycle is about 25 seconds, but at no time does it sound like the engine is about to stall out. I heard it stumble once, but that's it.

But more recently, the whole jeep has been vibrating at an idle like the rotating assembly is out of balance, but it doesn't knock any more or less than it did before. Actually, when I got back from grocery shopping I couldn't hear the rod knock that it developed this winter. Is this a sign of a bad motor mount?