cruiser54

Just keep checking the resistance as you go. Don't trust their crimps. I cut the crimps right out and them solder the wires in a bundle myself.

Your IAT looks just fine. You could always test it using the manual I sent you if you wanna. CTS can be in either hole. Near the CTS is a 10 digit part number on the block. Get that and I can tell you the year for sure.

They put the CTS in the rearmost hole. That other harness (three wires) goes to the oxygen sensor in the exhaust manifold. The knock sensor threaded in JUST above the oil pan into the block. Not into any passages or anything. It's just there to "hear" engine pinging. PM me your email address and I'll send you a real good Renix manual with diagrams, descriptions, and diagnostics.

Good progress. The one photo is of the IAT. Unplug it, unscrew it and clean off the tip of it with throttle body cleaner. You'll understand when you see it. A little dab of Permatex #2 smeared on the threads before you put it back in. That connector in the one photo looks to be for the knock sensor and actually has part of a busted knock sensor still attached. It originally attached to a threaded hole in the block just above the oil pan. It is not critical to engine operation at this point. The CTS should be threaded into one of those 2 coolant passage holes like in the diagram you posted. Generally, the most forward one. The harness for the O2 sensor, CTS, and knock sensor runs down by the front of the intake manifold BTW.

But the distributor shouldn't be wobbling. Check the play in it when you have it out.

Probably. Have you replaced your oil pump lately or had the dizzy out for any reason?

HEI will drop right in. 4.2 intake with a Weber. Woohoo.

Good job Marie. The sender shroud thread right in there. They're all standard thread. They go in at a slight angle so be aware of that. C101 is in need of cleaning for sure. They all are at least once in their lifetime! I've tried to find a part number for the TB to MAP hose but haven't had any luck. Just using rubber line isn't recommended either. Tha line needs to run in a downhill fashion from MAP to TB with no low spots. A decent parts store should have the plastic tubing. You can remove the rubber ends off yours and re-use them on the new tubing with just a small dab of adhesive to hold them on. The tubing can be bent using a hair drier. IAT is directly behind the throttle body and has 2 wires to it. Remove it and spray off it's tip with throttle body cleaner. They get gunked up and send faulty signals to the eCU. Got your meter yet?

2nd relay from the front is the fuel pump relay.

The sender and sensor for the coolant are NOT a combined unit in an 88. The CTS is located on the driver's side of the engine block. The sender is located at the driver's side rear of the head. I wonder if the guy put a later model engine in there that has no provision in the head. The C101 connector on 1987 and 1988 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before. Almost every critical signal between the engine sensors, injectors, ECU, and some to the TCU, travel this path through the C101 connector. The C101 connector is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time. Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth. If you have a small pick or dental tool, tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter before bolting both halves back together. 　 Revised 07-17-2012 IAT is screwed in to the intake manifold just rearward of the throttle body and has two wires on it. C101 is indeed the connector near the master cylinder and it carries a BUNCH of signals between your computer and fuel injection system. Try this, and it esplains a bit more about it. Renix Jeep C101 Connector Refreshing 　

Yes. The IAC will affect idle but not cause rich running. Rich running will cause crappy idle though. Richness at idle can be caused by a faulty oxygen sensor. Cold only extremely rich running is caused by, in this order, MAP, CTS, and IAT. Your 88 has the dreaded C101 cnnector. Have you addressed that?

Good idea. Unplug the electrical connector at the MAP and check it out. Did you ever get a meter?

Make sure the hose/piping from your throttle body to the MAP sensor on the firewall is flawless. No pinches, cracks, melted spots, loose boots etc.

You got it!!!

-------------------------------------------------------------------- The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea. CLEANING THE JEEP 4.0 IDLE AIR CONTROL Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to) “Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it. Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Process of elimination is good. Have you ever cleaned the throttle body and Idle Air Controller also known as IAC?

First place to look with your symptoms.

Bolt J4006700 Washers J3236434

http://www.elcaminocentral.com/showthread.php?t=27192

The fuel pressure rises when the hose is removed from the fuel pressure regulator. What that regulator actually does, is provide 39 PSI in the rail and that's plenty to run at throttle. It reduces the fuel pressure for idle.

That is normal where the line plugs into the throttle body.

Check the hose/piping from the throttle body to the MAP sensor located on the firewall directly behind the valve cover. Is it plugged into the throttle body tightly? Are there no crimps, cracks, melted spots in the line?

It's hard to pinpoint anything right now until we find out about the fuel pressure. If the fuel pump pulls fuel and air alternately, there could be a fluctuation in idle, not because of sensor readings, but because of the fuel pressure fluctuation. With less than 1/2 tank of fuel, you won't have to drop the tank.

Check the pressure as sugested first. I'm concerned about this. You might have a torn/split hose in between the pump in the tank and the top of the unit. That's easy. Buy a $15 to $20 digital multimeter and we can talk you through anything electrical.

Fuel pressure should be rock solid at 39 PSI at idle with the vacuum hose disconnected from the fuel pressure regulator and 31 PSI with it plugged in. Don't go chasing sensors just yet. Do you have a voltmeter and know how to use it?