My buddy has a 4 cylinder Jeep that has started cutting out when he is running along maintaining a constant RPM.

It usually runs fine and he has replaced the wires, plugs, cap, and rotor but not the coil.

I thought it may have been a bad O2 sensor behind the Cat but he does not have one behind the Cat.

Any ideas what may be causing this?

My next guess was maybe a fuel regulator.

 

I had an 86 cherokee that would do the same thing, it died one day and would not start. I left it there over night and in the morning I came back and it started right up. Never had any problems with it again, and never figured out what it was.

 

is the engine light on at all? try a good injecter cleaner like lucas, i hads the same problem with my 95 yj but i changed the o2 sensor, fuel filter and used the injector cleaner , and it cleared up , also the cats on those like to get clogged up after a bit too.

 

No his Check Engine Light is not on.

He did mention it backfireing on occasion through the intake?
So would that sound like a clogged cat?

This may be his excuse to cut the cat out and start trailering it to the lease.

 

He replaced the O2S and it is running fine

Thanks for the help; he emailed me the other day saying thank you.

Said that it was running smoother and had ran fine without a warm up;

previously that was one of the times it would happen.