[BigTime4x4]

2.5 Liter TJ engine running very bad, no power. First let me give you some background info. Please read...
I purchased this jeep last year. The guy did a lot of things to the jeep, and I really dont know what I have. the title says its a 97, but parts from the engine say its a 96. and there are like 4 different VIN #s on various body panels. Looks like I got a frankenstein.
what the jeep has as of right now. Dana 30/35, 488 gears, detroit locker in front welded rear, yukon shafts and super joints, 35"Boggers on bart wheels. stock fuel tank removed and replaced with fuel cell from summit, with after market pump. 2.5 4cyl

It ran kind of poorly and could only get up to 48mph, but the service engine light didnt come on so I just figured it was a typicall wimpy 4cyl thing.
What I have done in the past couple of days is removed dash and discovered the lights were removed from the gauges, this is why the service engine light was not coming on. I installed new gauges and read the service codes and it read 3 different codes. P0132 Oxygen sensor high voltage bank one sensor one. P0121 Throttle position sensor signal. P0551 Power steering switch.
I did an inspection under the jeep and saw that the front o2 sensor had 2 cut wires on it and that the rear 02 sensor was not even installed in the pipe, it was just tied up hanging out in the open. I replaced the front o2sensor with a new one, and installed the original one in the rear. went for a test drive and it seems like I had instantly gained a lot of power. I drove it for 20 minutes and was able to get up to 55mph. Then drove it back to parts store to check codes again. Even though it was running better it would still missfire on occasion, I it just seemed to me it should have better throttle response. I read for codes, and the only code that poped up was p0551power steering switch. I dont think this is why its running bad. So I left the parts store and on the way back home it started loosing a bunch of power, misfiring and then it died on me. no power, no nothin. I finially got it started, and back to the shop. I went ahead and replaced the TPS even though it was not reading a bad code for it anymore. still no change. The jeep has awefull almost no throttle response past 1/4 throttle. and back fires and misfires runs worse now than it did before I started, but the service engine light is not on anymore. This doesn't make any sense. Any help from you jeepers would be much appreciated. Thank you

[TheBoogieman]

I'd check for a clogged catalytic converter.I had a clogged cat and it burned up the tranny before I could get home.The vehicle wouldn't go over 30 mph.It's very common to have a bad cat on 97-99' Jeeps.

p.s The Jeep was made in 96',but there are no 1996 model Jeep wranglers.

[clintrivera]

With the aftermarket tank and pump, I would check the fuel pressure under load as well.

[BigTime4x4]

I should have mentioned there is no cat converter. Just headers, straight pipe and muffler.I will try to find a fuel pressure tester and see whats going on there. Does anyone know what kind of pressure it should be reading?

[clintrivera]

50psi +/- 5 psi

[bigred33]

New plugs, cap, and wires just for a cheap maintenance check. Then I'd check the ignition coil and alternator as well. Could have some failure about to happen there.

[4banged]

So you bought it running like this (sounds like someone else made the mods)? Even with 35's, a proper running 2.5 with 4.88 gears should have decent power (certainly more then 48mph).

[clintrivera]

Originally Posted by 4banged

I would think that the downstream o2 sensor would send bad info if the cat was removed but just guessing. So you bought it running like this (sounds like someone else made the mods)? Even with 35's, a proper running 2.5 with 4.88 gears should have decent power (certainly more then 48mph).

The downstream 02 sensor has nothing to do with the way the car runs. It's for emissions only.

[BigTime4x4]

When I baught it, it didnt have any o2 sensors working on it, but I didn't know that at the time. Also it was off road only very rough shape. and could only trail ride it up to 20 mph when I got it. The guy I got it from had it 4linked with tractor links and didn't know how to weld. stuff was actually falling off of it. I have put a ton of work into it over the past year, rebuilding the whole suspension and links and finally after I put new gears and axles under it, Im trying to drive it on the street.

[BigTime4x4]

I agree with you about the cat. I will install one tonight, and let you guys know whats going on. If you have any other ideas, feel free to comment.

[JBTJ]

Have you done a compression check?

[clintrivera]

Originally Posted by BigTime4x4

I agree with you about the cat. I will install one tonight, and let you guys know whats going on. If you have any other ideas, feel free to comment.

Installing a cat will make zero difference.

[BigTime4x4]

IM confussed... First you say the downstream o2 sensor would send bad info if the cat was removed. I agree so thats why I was going to install a new magna flow high flow cat tonight. But now you say it will make no difference.IM Just wondering why?

[JBTJ]

Have you done that compression check yet? That will tell you allot of things. I think your barking up the wrong tree with this cat and muffler stuff.

[clintrivera]

Originally Posted by BigTime4x4

IM confussed... First you say the downstream o2 sensor would send bad info if the cat was removed. I agree so thats why I was going to install a new magna flow high flow cat tonight. But now you say it will make no difference.IM Just wondering why?

I didn't say that. I said the downstream 02 sensor has nothing to do with the way the car runs. A missing cat won't make a difference either.

Check the fuel. Low or inconsistent fuel pressure will make it run the way you describe.