jeep lost it's get up and go

I have a 93 I6 automatic. Friday me and the wife depart for PA to go to rausch creek for the weekend, about a 9 hour drive from where I live. The jeep does fine until we get into PA where it seems to start hating the mountains. About 2 hours out I notice the jeep wont rev above 3500RPM. Weird I thought, but no big deal, probably just the ups and downs of the hills. Well then I noticed It wouldnt go above that on the downgrades either. So i tried flooring it. It jumped up to 4000 but the speed actually decreased, then it jumped back down to 3500. Made it to rausch creek, did the weekend wheeling thing, then decided to head home yesterday. On the way home, It was doing the same thing again. Made it almost impossible to pass anybody (could only pass if I had a long downhill stretch). Normally I go 80 -90. (lead foot, I know.) so being limited to 75 sucked for me. by the time I got into ohio my rpm was limited to just under 2000. if I tried to push it above that, it would jump up to 2500 and then the engine would bog down like it down shifted. so I had to drive the 4 hours through ohio at just under 2000 rpm with a max speed of a bout 55 - 60 :banghead:. if I popped it into neutral, I could rev the engine no problem. But in drive was where it was giving me a hard time. Also i could not speed up to merge with traffice properly. glad it was late at night at not much traffic. I havn't gotten into engine systems or transmissions yet so im not very proficient in this area. Any help would be appreciated! Thanks!

Is your voltage good? Low voltage could cause this, but you probably would have died before you made it home. Next thing to check is your fuel pressure and volumn. Rent or borrow fuel pressure gage. It should be about 50 lbs. Then check for volumn of fuel pumped in a given time. We'll have to look up the spec. I think your model has a fuel filter underneath that can be changed. Might be good PM just to change that.

if it where the fuel system would it not rev in neutral as well? I'll have to look for a pressure gauge.

clogged cat conv? exaust unusually smelly or does it seem better when its cold

X2 on the clogged exhaust/CAT. One test for the CAT is to hit with your hand and listen for internal rattles. Rattles imply deteriorating innards that clog the exhaust system.
Also, check fuel pressure and change your fuel filter.

I guess I would unplug the TCM, drive it shifting manually, and that would at least point you in one direction or the other.

plugged cat maybe, if you drive around for a bit with it like that and look at it, it should be glowing cherry red if its a clogged cat. also a vacuum gauge would tell you if its a clogged cat.

Fuel pressure, clogged cat, throttle position sensor come to mind here....fuel pressure and TPS can be easily tested. Disconnect cat temporarily or exhaust can be quickly analyzed to check that component. Let us know what you find....

I just went thru the same exact thing. My engine would rev up to 3000 rpm but lose power. I couldn't get over 45 mph and couldn't pull even the smallest of hills worth a damn. Turned out to be a plugged catalytic converter. Good luck.

joe_peters said:

I guess I would unplug the TCM, drive it shifting manually, and that would at least point you in one direction or the other.

Click to expand...

Im not sure what the TCM is. Remember, engine FNG

Banditt007 said:

plugged cat maybe, if you drive around for a bit with it like that and look at it, it should be glowing cherry red if its a clogged cat. also a vacuum gauge would tell you if its a clogged cat.

Click to expand...

how can I use a vacuum gauge to test it? perhaps i shall go on a half hour drive this evening.

birchlakeXJ said:

Fuel pressure, clogged cat, throttle position sensor come to mind here....fuel pressure and TPS can be easily tested. Disconnect cat temporarily or exhaust can be quickly analyzed to check that component. Let us know what you find....

Click to expand...

i tested fuel pressure and it's slightly above normal, no big deal . how do i check the throttle position sensor? As far as disconnecting the cat temporarily, I honestly have thought about taking a hacksaw to the whole damn thing. i figure I should get it replaced before I move to california in 8 months anyways.

I havn't had time to do much checking on it I just got back to work from a weeks vacation and it's been hectic, the navy wants you to do WAY to much paperwork.

i really appreciate everyones help and patience. Thanks guys.

I had been living with less power for years. Replaced the TPS and things seemed to perk up a bit! Although it could be the cat as everybody has mentioned thus far....

Good luck.

Squidmonkey said:

how can I use a vacuum gauge to test it? perhaps i shall go on a half hour drive this evening.

Click to expand...

Connect a vacuum gage to the intake manifold with a tee or possible disconnecting a vacuum line that runs the heater vents, etc.. Start it up and let it idle. If the gage gradually shows less vacuum, it indicates a clogged exhaust.

I know this is an old post and im reviving it... But I thought i would let everyone who chimed in with ideas and suggestions know, that after not being able to do any serious testing for awhile (I work a lot and only live 3 miles from work, so the problem didn't bug me on short trips) I eventually just replaced the exhaust system. No more problems. Thanks for all the help.