muffler issue? what is this?

i have a 96 sport, auto 4.0, and recently, especailly when car has been driving for a few minutes, there is a kind of grinding/whining sound that comes at just around/over 2k rpms in 1st and 2nd gear.

the exhaust has also gotten louder at idle- if im standing behind my running xj in park, the exhaust sounds throaty, kind of sick, it has been progressive and didnt used to sound like that.

it feels like some power is being choked too.

i took it to my auto place- they said they couldnt hear the noise when driving (one of those noises- if im looking for it it wont do it, but its been so lound ive had friends laugh at times when we were driving uphill) and that there were no leaks in my exhaust they could find....

do i just need a new muffler? whats the deal? any help would be appreciated

nothing? i forgot to mention how drastically gas mileage has gone down too- this weekend got around 300 to a tank on a 400 mile highway trip- used to be getting about 350 maybe more....

12GaugeXJ said:

Maybe a cat conv?

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Try beating on the cat converter with your fist and see if it rattles like a bunch of crap is loose inside.


Cracked exhaust manifold would account for noise and mileage loss, but I don't think it would make a grinding/whining noise. More like a sputtering/buzzing.

lilredwagn said:

Try beating on the cat converter with your fist and see if it rattles like a bunch of crap is loose inside.

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DON'T BEAT ON THE CATALYTIC CONVERTER.

By hitting it directly you risk killing it prematurely. Better to grab the exhaust either side of it (obviously, you want to do this with the exhaust cold) and shake it, both up and down as well as side-to-side. If you get the same rattles suggested above, then yes, it's likely gone. A plugged catalytic converter can account for a drop mileage like the one you're seeing.

hate to break it to you- my cat is next to new, replaced probably 2 months ago. its still shiny...

i forgot to mention i recently had a tune up too so tune up parts arent the gas mileage reason....

my gut is telling me muffler for some reason but auto place says nope any advice? something is off that is for sure...