Hello Guys and Gals, I have a question that may have a very simple answer, but one I have seen little mention of.
I have a 2006 WK Limited, 2WD with the 4.7 V8, very reliable… But quite often after start up, I experience sluggish acceleration and the sound of a rushing fan. As though the engine is working hard to muster the grunt as I reach highway speed. This occurs even at parking lot speeds. This is accompanied by a hesitation of the transmission… Interestingly, the tachometer shows no indication that the engine is working unusually hard.

After highway cruising for a short while, everything is much more relaxed. No fan noise, or trans hesitation.
And the engine just purrs and lopes along like a V8 should, providing plenty of power, even from a stop.

I understand the transmission is adaptive. So my assumption has always been that the trans is not really letting the engine do it's thing, until it has "adapted" to what I'm trying to do with my right foot. I don't know, maybe that's hogwash, but I've always been curious about this dual personality. Any ideas? Thanks!

 

First off, the 4.7 is not extremely reliable. Very common to have issues with the heads. Second, try disconnecting the battery and go through a relearn procedure. After that drive it as you usually would, don't baby it but don't beat on it.

 

What's the ambient temps when this is happening. Just curious about something.

 

what is a relearn procedure and how is it done?

 

Okay, here's my theory. The "adaptive" part is a computer learning process where the transmission control module learns your particular driving habits and adjusts shift points to your use of throttle commands under certain situations, like do you need extra power to merge into traffic on a daily basis?

My 2000 42re trans used to have problems trying to decide which gear to be in when I booted it in the ash because I seldom needed to. I took my WJ to the dealer for a series of recalls for seatbelt adjuster bolts, intake manifold heat shield, and a computer reflash. Since the reflash, the transmission seems to shift better when I ask it to do something unexpected.

All this boils down to is you may need a computer reflash, that is modifying the program to restart the learning process. It's just a theory, mind you.

 

With the XJ, apparently to put the jeep in fast learning mode, you ned to ground the positive cable for 30 seconds. Attach. Put key in ignition, turn to run, headlights on then off then start. That burns the stored electricity. There's a more proper technical way to state what I just said but its Monday.

 

It might just be the noise of the fan giving the illusion that the engine is working hard and the transmission is slipping. The fan clutch will be stiff when it's cold and loosen up once it warms up a little.

 

Lol, I love the sound of my fan clutch on a cold morning. Sounds more truck like. Idk.