Jeep Cherokee Engine Code P0171

1999 Jeep Grand Cherokee check engine light. Codes = p0171 Map sensor, tps, iac, o2 sensor all replaced.
Question:
I'm getting a p0171 code and getting horrible gas mileage. I do hear an exhaust leak and i'm wondering if an exhaust leak pre catalytic converter can cause this. I'm also getting a rough idle. Any help would be greatly appreciated.

Answer:
There are several things that can cause your P0171 and running poorly in your Jeep. First, check all the fuses in the underhood fuse box. If one for the O2 sensors heater circuit is blown, it will cause these problem.

You mentioned an exhaust leak. If it is a cracked exhaust manifold, then yes that may be the problem. Common on this truck.

Other possibilities are a bad vacuum leak. That will cause lean condition, code P0171, rough idle and bad fuel economy since the computer is constantly trying to adjust for the lean condition.

Contaminated fuel is another thing. Take a fuel sample in a clear glass jar and let it sit. If it separates into 2 different sections, you have bad gas. Another test which requires special equipment is an alcohol content check. High content will give all your problems.

A bad computer would be the last thing to check for, but can also be your problem. This would very hard to determine without looking at live computer data.