Topic: Backfiring

[Reddog]

Hello,  I have a 93 yj 2.5L. I had a magnaflow exhaust put on since my old rusted. I then found that my cat converter had been hollowed out. (I'm second owner) When I down shift or let off the gas at high rpms it backfires. I dont know what it is. suggestions?

[jfrabat]

Hello,  I have a 93 yj 2.5L. I had a magnaflow exhaust put on since my old rusted. I then found that my cat converter had been hollowed out. (I'm second owner) When I down shift or let off the gas at high rpms it backfires. I dont know what it is. suggestions?

Backfires or gurgles (dont know the correct term, but I think it is explicatory what I mean)?

[Reddog]

No backfires.  If i time it just right i can scare the hell out of the people next to me. I loud POW. In between shifts at high rpm and when I let off the gas from high rpms

[dwtaylorpdx]

Pieces of the cat may have gone down stream and lodged int he muffler outlet building up unburnt fuel vapor...

Dave

[jfrabat]

Yeah, I agree; this happened to me when I blew out my cat.

[MYSTANGT]

Can we just cut the converter out completely and weld in a straight pipe in its place?

I have a 97 TJ so I am already OBDII and i am wondering if that will trigger the CEL, because I wont pass emissions with the CEL lit up...

[sharpxmen]

Can we just cut the converter out completely and weld in a straight pipe in its place?

I have a 97 TJ so I am already OBDII and i am wondering if that will trigger the CEL, because I wont pass emissions with the CEL lit up...

to pass emissions you will need a cat - even if they won't look under for it you still won't pass emissions, so the CEL is your last concern for that.

[Reddog]

I dont think that could be it ,because it was done before I bought my jeep.  I did have a Pace setter headers put on along with the muffler. I asked the guy to clear my cat, Which he declined, and later told me it was already done. This was all done last April and it still does it. If its unburnt gas could it be spark plugs, wires, ect. I have changed the plugs, but not the wires.

[sharpxmen]

I dont think that could be it ,because it was done before I bought my jeep.  I did have a Pace setter headers put on along with the muffler. I asked the guy to clear my cat, Which he declined, and later told me it was already done. This was all done last April and it still does it. If its unburnt gas could it be spark plugs, wires, ect. I have changed the plugs, but not the wires.

the practice to "clear" the cat is very screwy as there is no way you can remove all the ceramic in there w/o cutting it open. so loose parts can make it into the tubing and muffler (but i'm not saying that's what the problem is, just a potential issue). if you feel that it could be your problem i would spend $100 on a cheap set of cat/muffler/endpipe and replace them.

[MYSTANGT]

to pass emissions you will need a cat - even if they won't look under for it you still won't pass emissions, so the CEL is your last concern for that.

So it will NOT trigger the CEL to come on, correct?

And if not, why do you think that I would have issues passing? Since i am already OBDII, in NY all they check for is that the codes are clear & no CEL is on...

Sorry but i am a bit uneducated on the emission systems 

[sharpxmen]

So it will NOT trigger the CEL to come on, correct?

And if not, why do you think that I would have issues passing? Since i am already OBDII, in NY all they check for is that the codes are clear & no CEL is on...

Sorry but i am a bit uneducated on the emission systems 

since you have 2 O2 sensors there could be a code triggered regarding the cat efficiency. You will not pass emissions since that's what the cat does - your exhaust emissions will be out of the acceptable range w/o a catalytic converter.

not sure what they check for in NY, over here (BC, Canada) regardless if you are OBDII or not an emissions probe will still be inserted in the tailpipe.