In the past month my 4.0 has seemed to lose quite abit of power and it has me quite puzzled. My tj operates perfect around town and does quite well on the highway cruising at 65 mph. The problem is that when I start pulling a hill it falls flat on its face, most of the time I find myself downshifting into 4th gear. I can tell you up until a month ago I never had this problem, I could pull the same hills in 5th gear and keep excelerating. Here is what I have done so far with no luck:
Scanned for codes, none present.
Replaced spark plugs, gapped at .035
Replaced the rear catalytic converter (was ratting but not plugged)
Replaced all four oxygen sensors (ouch) upstream O2's were operating fine but both downstreams were lazy.
Replaced the air filter
Replaced the tps (voltage readings a little low on WOT)
Performed a compression test and a cylinder leak down test, all within acceptable range.
Checked fuel pressure
Road test vehicle with scanner to observe system functions, all o.k.
Like I said around town and cruising at 65mph on a flat stretch of road is no problem, as soon as the jeep hits any sort of incline it dogs right out. The only other thing I wanted to mention is under a load I get a strong ammonia smell coming from the exhaust. Anyone have any ideas? Larry feel free to chime in.
Btw....it has 4.88 gears and 115k on the ticker.