Well, I think I am chasing an electrical gremlin. 1999 Jeep XJ, 4.0. I was driving this morning and after about 10 mins my speedometer zeroed and wouldn't move. Then, as I stop at a light my XJ dies. In order to start it I need to give it gas. Soon after the check engine light comes on. So I go to autozone and the codes read P0505 and P0500. I don't remember which is which, but one is IAC and the other is speed sensor. I kinda figured that. The battery is maybe 6 months old and it tested good with the meter and load test. Then on the way home the gas gauge stopped working(reading E). So I figure there is a ground or connector somewhere that all are connected to.
The work I was doing the night before was...reinstall front DS, drained radiator via petcock and filled with cleaner and topped with water(obviously spills on both sides), and swapped out resistor pack for blower(only worked on 4). These do not seem related, but who knows? The stalling happened about a month ago for about 5 mins then everything worked.
So I know I can change IAC and speed sensor, but what is the chance they both go bad at the same time? I got electrical cleaner and sprayed most connectors in the engine bay. I am sure someone has had something similar to this and I hope you can help me out. I try to do most work myself, but electrical gremlins aren't my cup of tea. I hope someone can help me out!
EDIT: The mechanic changed the IAC and it started to idle high and they added new grounds to battery and fender. They checked all grounds again and its still not working. Well I came to a crossroads and either needed to take it to another shop or get a computer. I do most of the work on my Jeep so figured the cost of a computer shipped is a little more than diagnostic fees and troubleshooting. So, my new computer arrived and BAM! gas guage goes up, idle right at 800rpm and when driven, the speedometer works!! I know most people say that the computer never quits...well, on occasion it does. Thank you for your tips and I hope this helps someone else. Basically, my Jeep is like my ol' lady...High Maintenance.
Last edited by lucas-3; 12-13-2012 at 12:21 PM..
I decided that I didn't want to throw parts at it and took it to a mechanic. They have had it for 2 days and are also stumped. They think it might be the computer because it is throwing more codes. What are symptoms of a bad ecm, ecu or pcm...whatever you want to call it? Also, how are the computer exchange places, are they decent quality?
The ECU is probably the LAST thing that will fail in the electrical system of the XJ. Before you possibly waste money on something that won't fix your issue, find another competent shop that will properly diagnose your issue.
WANTED--MJ Comanche to restore. Must be solid, (relatively) rust free chassis. Send me a PM if you have a line on one that is for sale.
So-called "mechanics" who don't know anything always claim "computer" when they don't know what's wrong. Tell him this... "Ok, replace the computer. But if that doesn't fix the problem, take it off and put my old one back on. Because obviously, that wasn't the problem."
See what they say.
Remember, you don't pay a shop to WORK on your Jeep; you pay them to FIX your Jeep. There is a difference.
The road goes on forever, the party never ends....