warthog

98 XJ 4.0L 4WD

Ran the enigne a couple thousand miles with a cracked head and now after replacing the head, its bogging down every now and again.

I have checked everything i replaced, no leaks that i have found.
It idled perfect for about 2 weeks theen started this. No CE light

It happens at idle but mostly when i go in reverse. normally it idles at 750 but will bog down to 250 or so.

I read running the engine with a misfire for a long time can damage the cat. In return causing idleing and driving issues

95Cherokee

Unbolt the exhaust pipe at the header and drive around a little and see if it still does it.

As a disclaimer I will add, go to Canada before bypassing the Cat.

superj

a bad cat will usually cause problems in the higher rpm range versus idle. at idle, it will usually run normal because the clog is not bad enough to cause any problems where as at higher rpm you are pushing through so much exhaust its backing up in the cylinders and chocking out the flame. also, a clogged cat will cause you to run warmer then normal

warthog

I have been running about 10 degrees warmer than normal. I use to put put around at 210 but now it is normally around 215-220.

djb383

On OBD-II systems ('96 up), a bad cat should trigger a CEL. Have your ambient temps been higher lately as well? Check your intake sensors....IAC, TPS, MAP and clean the TB and IAC passage way.

warthog

slightly higher but with the rough idle i was trying to put 2 and 2 together. I am going to clean all that plus seafoam it maybe this weekend

djb383

Cap, rotor, wires, plugs?