Possibly a Faulty o2 or MAP sensor?
I have a 93 YJ with a 4.0 litre. It has the correct multi-point and pcm engine. For as long as I've owned the Jeep (3 years) it always seemed to have a rough idle. Along with the rough idle it gets terrible gas mileage (even bad for a 4.0 on 33's) and the exhaust is extremely rich. I haven't been able to check any codes because of the OBDI and there is no check engine light. However i believe I have narrowed it down to three possibilities. Either a crack in my exhaust manifold, a bad o2 sensor, a bad MAP sensor, or a combination of the three. I have deleted my CAT but I don't believe my mixture should be this drastically rich, however i could be wrong. I have yet to do any tests and only first started really trying to diagnose my problem recently. I'm just looking for any general insight on if any of my ideas are correct. Thanks.