YNGFrankenstein

Symptom is idle starts around 800rpm and fluctuates to +1500 about 8-10 seconds after starting. If I don't shut it off, it continues to fluctuate and climb. From my research, this is possibly a vacuum or sensor issue, so maybe shouldn't be worried about the wiring and focus on the vacuum, but diving into the wiring has helped me figure out the difference between my jeep and a stock one. The truck has a lot of aftermarket modifications, so i'm assessing what it will take to give me and others a baseline to troubleshoot issues moving forward.

Good points. "Unless the thing is completely butchered" is likely where we're at. As noted in my reply to Ωhm, I had the truck towed to two different shops and neither shop would work on the truck with the wiring in its current state, which is why i'm navigating down this path. The recommendation from one shop was to find a donor stockish XJ to wipe the slate clean, but before I sink too much more money into the project, I figured I would spend some time on the electrical myself.

Hello All, I'm in the process of navigating the wiring modifications done by a previous owner on my 88 Jeep Comanche 4.0L Automatic. I purchased the 88 electrical manual and found diagrams for both the Engine Harness (picture attached) and Engine Control Harness. I already have a replacement Engine Control Harness from a 1990, but would like to replace the "Engine Harness" as well. My questions are, is there another term used for the Engine Harness? I've looked online for an Engine Harness replacement but I only find Engine Control Harnesses. Also, the previous owner deleted the ECU to Engine C103, C104, and C109 connectors and has some under hood lights spliced into the Engine Harness. Is deleting the ECU to Engine connectors a typical move? Best,

Ok. I was able to troubleshoot over the holiday weekend. I checked the flexible rubber line between the chassis and rear axel as AZJeff suggested. It was an aftermarket part installed by the previous owner and was still in good shape. Next I opened the line coming out of the Master Cylinder's rear brake reservoir and couldn't get any fluid to come out. Then opened both ends of the brake line going from the distribution block to the rear brakes and that was also clogged. I was able to eventually unclog that line by pushing air through both ends. Since the Master Cylinder was pretty grimy, and rebuilt ones are fairly inexpensive I replaced the Master Cylinder. After that, I ran some brake cleaner through the rear lines. Then I bled the brakes using the FSM procedure and it seems like i'm good to go. Other non-related issues are keeping the truck from running but that's a project for another weekend. Thanks to Eagle and AZJeff for the help.

Eagle, Thank you for the reply. Yes, I attempted to do a regular bleed on all four wheels, but was unable to get any fluid to come out the right and left rear bleeder. I tried adjusting the lever on the proportioning valve in all direction while attempting to bleed the rear brakes. I opened the lines going into and out of proportioning valve and found no blockage in the valve. I also opened the 3 way brass fitting (meeting lines are - front of truck, - proportioning valve, - rear brakes) and was able to blow out the rear bleeders by pushing air through it. So I'm thinking there is blockage in the line coming from the distribution block or maybe there is something else i'm not taking into consideration. Thanks agin,

Hello All, I am in need of some guidance for the rear brake lines on my recently purchased 88 MJ. I replaced the rear brake shoes, springs, and cylinders because the rear brakes were disassembled and missing parts upon purchase. After finishing the rear brake assembly, I attempted to bleed the rear brakes using the 88 Comanche FSM procedure which includes opening a front bleeder to allow fluid to flow through the by-pass line. Unfortunately, i've had no luck getting any fluid to come out of the rear brake bleeders. No fluid with front bleeders open or closed. I troubleshooted further by opening the brake line before it reaches the rear proportioning valve, but still no fluid. My next inclination is to disconnect the start of the rear brake line from the distribution block, disconnect the end of the rear lines, and attempt to remove any blockage. Any suggestions on the best way to achieve this or another path to for troubleshooting are more than welcome. Thank you,