JeepWJ36

I have a WJ with 178k and it has the same problem as described in this thread. Seems sluggish and will even downshift on smaller hills. Sometimes going up steep mountain passes I push the pedal to floor and first it just boggs down and looses speed then it shifts to 1st or second. It's always downshifting on the slightest hills when I press on the pedal to maintain speed. Like everyone else in this thread and even other threads it seems like no replacement of typical culprits helps such as fuel filter, pump, cats, plugs, IAC, TPS, TV cable checked...all compression and fuel tests normal, no brakes sticking, tires at 44psi. Did anyone figure the problem out?? I should also mention that this issue is also intermitten. It does it most of the time but then I have a few times where acceleration is great and no unnecessary downshifting. Since there are no pending codes, check engine lights I'm wondering if by any chance it's one of these things thats being overlooked:
1.I do have camber wear on both front tires and need to do the ball joints and inner steering link..maybe this is adding lots of drag?
-2. I replaced PCM 4 years ago with aftermarket PCM. Maybe it's not programmed correctly?

dave1123

A lot of this problem can be the spark plugs misfiring under load. This can be caused by lean mixtures and in extreme conditions, detonation,or electrode gaps worn large enough to not fire under high cylinder pressures. It may even be a weak spark rail on the 4.0. I've had this problem with my 4.0 on several occasions and a new set of spark plugs cured the problem. Later in it's life worn piston rings just couldn't generate high enough cylinder compression to product enough power to keep the speed up so it would downshift if the cruise was set. When I rebuilt the engine, I installed a Dodge Caravan V6 coil and plug wires and haven't had the problem since. This is the Ksuspension "Viper" coil system but built from parts I bought except for their harness extension piece.

If it's a 4.7 V8, I would suspect worn spark plugs to try first, or a new set of coils.

MSISSON

I'm having the same issue with my 03 WJ. I've changed plugs, 02 sensors, fuel filter, thermostat and housing, coolant temperature sensor, oil change, coolant flush(just for fun) and can never maintain more that 60mph with a tailwind going downhill.

Caish

Could have restricted exhaust, like a cat is coming apart blocking flow of the exhaust.

Caish

Check your fuel flow.
Pull the schrader valve on the fuel rail,
Use a paper clip jump the fuel pump relay.
Let it run into a gallon jug etc, for 60 seconds
Should have around a gallon,
Mine was weak only about 3/8's gallon in 60 seconds.
Repeat underneath pulling feed line to the pressure regulator, filter right in front of the tank...