I am experiencing a weird situation with my 2006 Grand Cherokee and I decided to ask for your expertise on this subject. The car is a 4.7 and has 100k miles on it.
The problem is, on hot days after a short drive when I put the car to park or natural, it first idles high (1100 rpm) after some time (around 30 sec) it starts to fluctuate erratically between 500-1100 (for 30 secs or so)and finally settles around ~550 rpm which is the normal idle position. After it settled, if I push the throttle, it again idles high and the same process repeats. While the gear is in drive, it idles around 550 rpm but I can feel it wants to idle more since when I am stopping at a stop sing or red light I need to brake a bit more as the car wants to move forward. Aside from that it drives normally without any power loss or noticeable change. This problem only happens in hot weather, so if it is not hot (by not hot I mean below 74 degrees F), it always idle at ~550 rpm regardless of gear position.
It doesnít seem to matter if the engine is cold or warm however, if I drive the car for long enough (20 min drive), the idle problem eventually disappears.
I first tough it might be resulting from the A/C, since my A/C is always in auto mode and kicks in in hot days just after starting the car. Turning the A/C off does help a bit (the car comes to normal idle rpm faster like 10 sec), but does not completely solves the problem.
I already cleaned the throttle body by gently wiping it and also cleaned the iacv motor but that didnít helped. Since it is a WK, like most of its kind, it also has a broken bold on the driverís side exhaust manifold
. I am thinking this my cause air to leak in and mess up the left bank oxygen sensor readings, which would explain the idle problem. However I cannot see why this would only happen in hot days. I recently changes almost every fluid in the car (coolant, tranny, and diffs) except transfer case, so I donít think old fluids is an issue here and their levels are in normal range.
I know there are many more things that can cause what I explained (injectors, throttle position sensor, etc.) but why any of this would be ambient temperature dependent.
Maybe you guys can figure out what is going on.
Thanks in advance!!