I replaced the IAC valve on the base of the throttle body. While it improved the idle characteristics slightly, it did not remedy my problem with the CEL coming and going. For the most part, the CEL light is on all the time.
I sent Wranglerfix a message a few days later and he returned my call in the evening and we had a long discussion. We came to the conclusion that my PCM is OK. The issue I have is that the mini cats most likely fouled the main larger catalytic converter and the ONLY remedy for the situation is to replace the entire system. The cat system on the 04 Wrangler is a poor design, and we came to the conclusion that the cats are probably causing the poor idle. He has experienced this in his work.
I have been extremely busy, but will get to this fix a little later on this year when time permits, Here is the plan. I am going to drop the skid plate but I have to figure out how to accomplish that in my garage, then remove the entire exhaust system and haul it to the dump. I have a new Walker exhaust system picked out at RockAuto,com that has a throaty sound to it. The system is made out of stainless steel, so it should outlast the original system. Walker does exhaust, so I am confident that their system will work, the engine will be able to breathe better, and I will probably experience a horsepower gain by switching to a system that is unrestricted/inoperative in the cat system.
Another recommendation from him was to disconnect the cat sensor at the large cat (the post cat sensor). His reason being that if there was nothing to compare to then it would not trip a CEL light (the pre cats compared to the post cat voltages). My question is can you just disconnect it and leave it at that, or is more required to trick the system into not seeing the post cat sensor?
I need to replace my system to get it to flow properly, then inhibit the sensor. That is the plan moving forward and can update as it progresses. For now, the Jeep is sitting cover up.
I recently had both exhaust manifolds off (4.0 engine) to replace gaskets. They are in good shape so I am sticking with them. There were no cracks.
Hoping I can re-use the exhaust mini-cat nut plates, they are nearly new and expensive!
