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adamfeather, Technician
Category: Jeep
Satisfied Customers: 86
Experience:  Master automotive technician ,ASE master certified,associates degree in automotive technology
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Vehicle: 1997 Jeep Wrangler, 2.5l 4cyl (113k miles) Problem:

Customer Question

Vehicle: 1997 Jeep Wrangler, 2.5l 4cyl (113k miles)
Problem: Check Engine Light, code P1071.
Rough idle (800-900 rpm), lacks power, consumes lots of gas.
Exhaust tip charcoal black, exhaust smells like gas.
Believe I'm hearing an exhaust leak while driving, but haven't located it yet.
Troubleshooting performed:
-Tightened loose exhaust manifold bolt (the rest are tight, intake & exhaust).
-Thoroughly cleaned throttle body, MAP & TPS sensors.
-Replaced pre-cat O2 sensor (problem went away for 500 miles, came back same).
-Replaced MAP sensor (no change).
-Clamped/sealed vacuum connections at manifold (rough idle improved, but CEL came back)
-Vacuum gauge hooked to intake manifold: needle fluctuates rapidly about 4 in/Hg & stays between 15-18 in/Hg. Vacuum drops when throttle is advanced rapidly to 3000rpm, then settles at about 20 in/Hg (still fluctuating).
Appreciate your help.
Submitted: 1 month ago.
Category: Jeep
Expert:  adamfeather replied 1 month ago.

Hello, my name is ***** ***** I'll be happy to assist you today. I have an associates degree in automotive technology, ASE certified with 15 years in the field. Sorry to hear about the repetitive problems on the Jeep.

Just to verify I assume it is a code P0171. not P1071? Just a typo?

P0171 is very common on this engine and over 90% of the time caused by faulty Pre cat/front o2 sensors. In your case P0171 indicates bank 1 sensor 1. Forgive me as I do not know your skill level some some things you may already know.

It is possible they failed again because of the way you mentioned the exhaust being very black like it is way too rich. Even if something else is causing them the fail if they are extremely sooted up they may need to be replaced again when you get to the root cause.

It is also fairly common and many times hard to find but the power steering pressure switch can leak fluid onto the engine harness and the fluid will wick its way down the harness and into the PCM or engine computer electrical connector. The fluid in the connector causes the PCM to see invalid o2 sensor readings. The PCM sees lean reading and thus the fault. Also the fake lean reading force the PCM to excessively richen the fuel mixture causing 02's to continually fail. This sounds like your problem and would be the first thing I inspect. Let me know if this helps and feel free if you need any further help on the issue.

Thanks ,


Expert:  adamfeather replied 1 month ago.

Hello, I hope all is well with the Jeep!

I just wanted to follow up to ask if your satisfied with your experience and whether I adequately answered your question? If not I will be glad to provide further information.

If you feel I adequately answered your question please accept the answer and rate my services if you wish. Because I am a private expert for Just Answer I only get paid for accepted answered.

Thanks again and I hope I was helpful!


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