I have been fighting this issue for the last couple of months. Finally, my Jeep would just do random misfires and go into limp mode. The way to find out if you are having a problem is to put your hand on the OPDA (Oil Pump Drive Assy) and see if it is vibrating badly. Believe me, you will be able to feel it.
Here is a little background. I have been getting random misfires and throwing CPS CEL's. My Jeep goes in to limp mode (when the motor will not go over 2500 rpm's and starts bucking) after about 15 minutes when the motor gets good and warm. After searching the forum for answers, I started changing out everything. Crank Pos. Sensor, Cam Pos. Sensor, spark plugs, catalytic converter, and oxygen sensors. The dealer even looked at it and said it was ok. I even went as far as running a compression test, seafoamed and cleaned EVERYTHING, and put dielectric grease on every electric connection on the motor and PCM. Even the ground connections were coated. And still no change.
Finally, while the engine was running I heard a little noise coming from the OPDA. When I put my hand on it there was quite a vibration. I pulled the OPDA and disassembled it. There are two metal bushings in the OPDA. There is one in the top and one in the bottom. My top bushing was wore out. There was about 1/8" of play. My Jeep has 95K on it.
The problem is in the oiling of the OPDA. There are no oil journals to provide oiling to the top bushing. Basically, late 04 til the end of production on the 4.0 Chrysler went to a Mercedes designed OPDA and programming on the PCM. This is a very piss pore design. If anyone is getting close to 90K on there Wrangler, you might want to keep a watch on random misfires. If your Jeep starts misfiring randomly, put your hand on the OPDA and see if you have a bad vibration.
Now to address the TSB on the OPDA. I have two dealers in the area and they will do nothing until you pay them to diagnose it. I got lucky with one of them because they did not charge me due to the fact that they could not find a problem. After emailing Chrysler, I received a generic message saying that they were sorry and were sure that the problem would be taken care of very quickly. That was a month and a half ago. Then I called Chrysler and got the same response from a person. There must be a form letter that Chrysler goes by. Right now there is a back order of over 250 OPDA's with over 20 Jeeps sitting at dealers and the owners cannot drive them. Dealers can look on the computer of an ETA and distributor. As of last week, there is no ETA and no distributor listed in the dealer computer. I was told by the dealer that meant Chrysler had no one to produce the part. After not driving my Jeep for almost a month, I found that unacceptable.
So, I put my thinking cap on and looked for a solution. I decided the remedy was a new top bushing for my OPDA. The machine shops here around town were scared to work on my OPDA. I finally found one that was willing to take on the project. The machine shop made me a new oil impregnated brass bushing and installed it into the top of my OPDA. The machinist said it should last for quite a while. Installation was a breeze and I got the LJ running yesterday. It runs as good as it ever has.
And by the way, my OPDA and cam gears look fine.
Good luck all 04 to 06 LJ and TJ owners.
2005 Unlimited Rubicon, too much junk to list!-sold
2012 JKU Orange Crush