TJ 4.0 loss of power

[mickxr6]

I have had the jeep for a while now and I have lost a lot of power in 4th and 5th gears. Off the lights 1st is great and so is second but third seems to have lost a bit of power with a feel that it has a miss half way through the rev range. Once I hit 4th response is poor and now the car struggles to get over 100km's in a slight head wind. If I go up a hill I have to drop all the way to 2nd because the higher gears have no power and I feel the engine missing again. I have replaced the coil, leads and dizzy cap but this has not fixed anything. I was wondering if anyone could point me in the right direction as I'm at a loss as to why I have full power in first and second but she dies on her ass in the higher gears.
Mick

[rhysTJ]

I have had the jeep for a while now and I have lost a lot of power in 4th and 5th gears. Off the lights 1st is great and so is second but third seems to have lost a bit of power with a feel that it has a miss half way through the rev range. Once I hit 4th response is poor and now the car struggles to get over 100km's in a slight head wind. If I go up a hill I have to drop all the way to 2nd because the higher gears have no power and I feel the engine missing again. I have replaced the coil, leads and dizzy cap but this has not fixed anything. I was wondering if anyone could point me in the right direction as I'm at a loss as to why I have full power in first and second but she dies on her ass in the higher gears.
Mick

what mods?
tyre size?
TJ's where never geared up well for highway driving in australia.
with the diff ratios being poor from factory.

[mickxr6]

Just a lift kit. Nothing else touched. I know that the TJ wasn't great for top end highway but I wish it still had the power it once had.