I have an 05 4.0L and the the top left piece next to the intake tube going into the throttle body there is a control of some sort that has a black plastic side piece with a metal dome on it. It is held on with 4 small phillips head screws. Mine is all rusty so I grabbed a nice clean one at the yard the other day along with the plastic side piece. When I took it off the junker there was a spring and some gear pieces. If I take mine off and replace it how much trouble can I get in screwing up the timing of these gears etc. Can I just replace the rusty dome piece or will that potentially mess up something as well. I think the part number on it was something like 3DRE-DA.