The losing power seems to happen more when it is cold but happens at other times too. When it loses power, it seems as though it is backfiring or loading up but the engine RPM's do not drop and if I hold the throttle it continues to lose power and then all of a sudden and just in a flash, the power loss stops and everything goes back to normal just like nothing happened. The power loss never lasts more than a few seconds and if I let up on the throttle instead of holding it down and then push the throttle again, the engine will act normal. Also, at very very slow speeds and extremely light pressure on the peddle, the engine (or trans.) Start to buck. I thought I heard a very faint pop in the engine compartment through the intake one time and then the engine kick back to life after its power loss spell. I have replaced the TPS, CPS. I did a scan on it once even though there're no check engine lights on and found that the O2 sensor seemed to malfunction once. I know the 4.0 engine better than most and have never encountered this problem before. The cracked exhaust manifold is cracked down by the collector and is not loud as you imply it would be and yes it is a good size hairline crack which is expanded when cold and as warms up it is semi sealed from the metals expanding. This is typical for the 4.0 engine with the exhaust manifolds. The Chrystler dealer had it for a few days and said it was the governor pressure regulator and it was replaced with factory parts and a new wiring harness and etc. Hope this helps as far as further explanation.
Wednesday, December 16th, 2009 AT 10:58 PM