Loss of power??

Okay guys, I have been working like crazy for about 3 months now and I'm finally going to be off this weekend and be able to tackle a list of things that have needed to be repaired for a while now. Need your help on where to start looking on a few problems.

First of all, 98xj sport, 4.0, AW4, with 187K+ miles sitting on 31x10.5 mt's with Skyjacker 3.5" lift. I recently replaced motor mounts with Brown Dog mounts but I have not welded the cracked manifold. Also, the catalytic converter is rattling like aluminum cans in a bag. No CEL's whatsoever. About a week ago I started noticing a significant loss of power, especially in the higher rpm's. Very noticeable when trying to pass someone or gain speed on the interstate. Would this be a result of the cc or the manifold? The manifold has been cracked for several months now, but it has gotten worse and louder. Any help on where to start is greatly appreciated.

Usually when there's a power loss after changing motor mounts, there's a vacuum leak somewhere (like a line disconnected). However, it's usually significant or total loss of power and immediate...not gradual.

Immediately after the motor mounts were installed, the throttle response was better and actually made the engine seem a little more peppy. The loss of power has happened over the last couple of weeks and it has been about a month or longer that I installed the mounts.

Samson04 said:

..... the catalytic converter is rattling like aluminum cans in a bag. ......

Click to expand...

Clogged cat = power loss

XSometimes you can tell that a converter is clogged because you don't go any faster when you push the gas pedal. Also, there usually is a noticeable drop in gas mileage associated with a clogged catalytic converter. A partially clogged converter often acts like an engine governor, limiting the actual RPMs to a fast idle. A totally clogged converter causes the engine to quit after a few minutes because of all the increased exhaust back pressure.

time for a test pipe!

That sounds like that is definitely part of the problem. It seems to run fine at low rpm's but does not gain any speed when you push the gas. I've also noticed in the last day or so that I have to really push on the throttle to get it to downshift. That may be a different problem. Isn't there a universal cat that can be used? The cheapest one that NAPA has online is $153.00.

summit has some decent cats from CATCO for less than 80 bucks

http://www.summitracing.com/parts/CTO-6575/

The price is very appealing. Has anyone ever used these? Does it cause a CEL? I don't want to save money and have a problem with the o2 censors.

i used the 3" in/out version on my 89 c3500 with a mildly worked over 454 and it worked great. Good flow, good sound...passed emissions.

Does that cat have the bung for the after cat oxygen sensor? Is it needed for your year XJ? For my 1996, I got the MPE-23226 also from Summit. My XJ needed 2.5" in and 2.25" out. This was a directly replacement.

to find out if it is your cat disconnect the exhaust at the manifold or take out the front O2 sensor and then drive it. It will be loud but if your power comes back you know it is the cat. Also the inside of the cat can end up in your muffler and plug that as well. :spin1:

Yeah, the whole exhaust is pretty much shot. I was planning on welding up the manifold and replacing the cat and muffler. All of my pipe seems fine. I just wasn't sure if that is what was causing my power loss. I thought if the cat was clogged it would pop the CEL because of the o2 sensor. I'm leaving work on a half day today and am spending the next few days tuning the old box up. That will include a new cat and muffler. Hope that's all it is because I've seen the gas mileage suffer too and I can't afford that now with gas prices this high!

http://www.summitracing.com/parts/CTO-6575/

Anyone know if this will work on my xj? I was supposed to be working on the heep this past weekend and had to go out of town for work. If this will work, I'll order one right now. Not opposed to doing a little modification, I have access to a welder and I'm decent at it. Any suggestions? I just hate to spend the $130 for one from Autozone.