blkcherokee

Ok my 98 XJ has been running all weird since my cat clogged my exhaust since that i have replaced both O2 sensors my cat an now its acting up even more.... when i start driving it sputters an pops then after that it will stop an then after sitting at a light my RPMs drop to i would have to say like 300 an runs rough ill put it in nutural an my RPMs jump back up to about 1200 any one have any ideas for me...... This week i am going to replace the cap, rotor, wires an plugs any thing else i should do? PLEASE HELP

IT'S AN XJ THING

https://www.cherokeeforum.com/f2/pop...utering-36678/

blkcherokee

already saw that i have around 160,000 on it i dont have the money for all that this just started happeing when my cat started breaking apart

blkcherokee

anyone else have any sugestions

Abovetimberline

Sometimes when the cat breaks up it ends up in your muffler and can cause a restriction,it is possible this has happened.
If it was running good before the cat went bad,then I would look into the muffler.

blkcherokee

i am getting a flowmaster exahust put on in the next 2 weeks or so but yesterday i had to cut off my tail pipe because there was some of the honeycomb still in it is it possible that there is more in my muffler which is causing this an also i had it running with the hood up an it sounds like i am sucking more air then it should you could hear the air sucking over everything else idk what this is i checked all vac lines an nothing

Chrkee313

Rip that thing off, Most likely it's throwing wrong info to the oxygen sensors and that in turn goes to the PCM and adjusts things like tps, iac, mat, map and more. Wrong information goin to your PCM and comin out of the PCM is bad news.

Abovetimberline

I would cut the exhaust just behing the cat but leave enough to so you can reconnect the muffler if needed and see if it helps.
It is also possible you created enough back pressure to cause a gasket leak,I had a head gasket blow from a clogged cat on an 89 pontiac grand am.

blkcherokee

well when i cut it off i stuck my hand at the exit i felt good presssure so if there is anything still in there it wont have a hard time getting out an do you think that a head gasket would cause my problem

Abovetimberline

I am not suggesting you have a blown head gasket I only mention that to give an idea of how much back pressure there can be and the damage it can cause,you would have some other indications like overheating and water in the oil,I think it is possible you have a restriction or maybe an intake gasket leaking,you can put a vacuum guage on it and it should be around 15" of vacuum,you can also spray some starting fluid around the intake and see if it changes your idle.

blkcherokee

how heavy is a stock muffler cause when i replaced my cat the stock muffler felt really soild an heavy cuase the cat was completley empty like nothing left in it at all an i pulled out 2 big pieces of i know there has to be more of it somewhere

Abovetimberline

They are not that heavy,but not sure of the exact weight. If your old cat has not brick left in it then it is possibly in your muffler,it is pretty hard for that stuff to get therough it.

blkcherokee

so its possible what i think is good back pressuse really isnt as much as it should this is my first time dealing with this an i should maybe speed up my flowmaster exhust
an that could still be my problem why i am sputtering

Abovetimberline

If your going to do it anyway then yea,you can also put a vacuum guage on it and it should read about 15" of vacuum,if it does then you maybe fine,if not then it may be restricted,vacuum guages are not expensive.
A muffler shop can also do a back pressure test but that cost alot more than a vacuum guage.
The only thing that has changed was the cat went bad,before that it was running good correct?

blkcherokee

yea before the cat went bad it ran like a champ no import could mess with it on the launch an the first few gears lol