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Old 04-11-2012
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Join Date: Apr 2012
Location: Springfield, MO
Posts: 9
Catalytic Converter or O2 sensors? P1152 P1131 P0155

Just bought a 2000 Ford Ranger XLT 4.0L V6 4x4, 5spd Auto, a couple of months ago...


Rough Idle - Sometimes it will have a rough idle and occasionally die. It doesn't seem to matter if the engine is cold or warmed up. This doesn't happen all the time. Sometimes it seems to be fine but eventually if left running long enough it will start to idle rough and about 30-40% of the time will die.
Loss of power - An example was right after buying the truck and driving home about 75mph it bogged down to 50mph. It also died at a few stop signs. Doing a brake test in the driveway, it will also bog down and sometimes while driving at in-town speeds you can feel it lose power and then it will pick back up and jerk back into running correctly for a bit.

It's throwing these codes:
P1152 - Lack of O2 switches - bank 2 sensor 1 - rich; ECM detected 02 sensor at its rich limit
P1131 - Lack of bank 1 02 transitions - lean; ECM detected bank 1 02 at its lean limit
P0155 - HO2S21 heater condition (Heated oxygen sensor Bank 2 Sensor 1); The powertrain control module monitors the oxygen sensor heater. The computer has recognized a failure in this circuit.

I had a local mechanic that I've known a long time and trust check it out and he thinks it's due to the CAT and not the O2 sensors or any issues with the EGR. He showed me where it looked like someone had cut a square out of the bottom of one of the CAT's (it has 2 in-line), and welded the cut-out square back. He thought they were trying to drill out the CAT to maybe make it sound louder or something.

I can't really afford to throw parts at the truck trying to figure it out. Any thoughts or help would be greatly appreciated.

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Old 04-11-2012
Blhde's Avatar
Join Date: Oct 2005
Location: Northern IL
Posts: 2,804
Vacuum leak, I would redo the lower/upper intake gaskets. They come in a kit with valve covers too.

That is where I would start.

After that a complete tune up. Recheck codes.

Gutting the cats will screw with the computer, and push the limits of the stock tune. Replace them as your last step, I think mangnaflow makes a replacement for 250.
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