uphill rattling

my 99 xj sport makes this rattling noise going uphill. a few weeks ago going up a hill it became weak and I hit gas to pedal, it had no power hardly made it up. I noticed oil pressure went down, so i change oil pressure sender. Took it around a few hills and everything seemed normal, pressure seems normal. But I noticed that there is this rattling noise coming from under jeep every time i go uphill, it does not matter how steep it is, the noise always comes up and the jeep feels weak.

any suggestions of what to look at? I took at look at heat shield and it's pretty tight. I do not see anything lose under there.

Crawl under the Jeep when it's not too hot. Give the catalytic converter a good wrap with your hand (not too hard) If you hear anything at all inside loose then the subtrate that makes up the internal converter has failed and it needs to be replaced. It would explain your rattle and loss of power. You can get an IR gun and check your temps pre cat and post cat to see if you have a blockage.

Beyond that I would inspect the exhaust system carefully and look for any points that might be rubbing or contacting.

I ll check that in the am. On my way home i noticed the noise doesnt happen all the time but when it does it happens at about 1500-2000rpms.

98NWCherokee said:

Crawl under the Jeep when it's not too hot. Give the catalytic converter a good wrap with your hand (not too hard) If you hear anything at all inside loose then the subtrate that makes up the internal converter has failed and it needs to be replaced. It would explain your rattle and loss of power. You can get an IR gun and check your temps pre cat and post cat to see if you have a blockage.

Beyond that I would inspect the exhaust system carefully and look for any points that might be rubbing or contacting.

Click to expand...

There's a rattle in the cat for sure! can i just insert a new cat in or do i need to bring to an exhaust shop?

Thank you for your help

If the substrate inside the cat has broken there is no way to repair it. It must be replaced. I would recommend welding or having one welded in to prevent drug addicts with sticky fingers from liberating it from your Jeep. I caught one in broad daylight once with a battery operated saw.

Are you getting any check engine lights? The downstream O2 sensor (after the cat) should be measuring cat efficiency, but I'm not sure if it would throw a DTC. I would think if you had a sizeable blockage you might get a code. I know the upstream O2 modifies fuel trim.

If it were mine, I would do a little more testing before I threw a new cat at it......they're expensive. Grab an IR gun and check your temps before and after the cat. I suspect you've got enough of a blockage that all the heat is eaten up in the cat.

Maybe someone will chime in with the numbers you should see post cat.......I would think they'd be less than pre cat but still pretty hot.

Had similar issues with mine, albeit it's 10 years older than yours. Horrible rattling sound. It was more of a noise than a vibration - and I ruled out the exhaust hitting the crossmember the only other thing I could think it would be. Replaced the cat (super cheap - only $105.00) at the local Advance. I bought a Magnaflow brand - was a direct fit and came with a gasket - but no bolts. No clanging noise now and runs noticeably cooler too.

Still have to stop by the local recyclers to see how much they'll give me for my old one. When I turn it end-over-end, it sounds like a single solid chunk of something just sliding around inside it.

I don't have check engine light on but during my smog test the report stated o2 sensor down stream not ready as well as other air flow components.

Sounding more and more like the cat is a goner. Looks like FreeJeepXJ was able to get one on the cheap. I thought they were much more expensive than that.

I just ordered one for 130$

freejeep88xj said:

When I turn it end-over-end, it sounds like a single solid chunk of something just sliding around inside it.

Click to expand...

Those would be your precious metals.

JeepNovice said:

I just ordered one for 130$

Click to expand...

Glad it was so reasonable. I hope that takes care of it for you.