Just bought a 97 wrangler, 4 cyl, 5 spd, 178,000 miles for a farm vehicle. Its in super shape and i plan on driving on the road some too, however it has a small problem. The check engine was on when i bought it. that factored in on the price. I had it checked before i bought it, o2 sensor. It drove fine with the check engine light on good power, responsive. I had it reset and drove it, when i went to 3rd gear it stalled. dropped to 1000 rpm and was unresponsive. i kept pumping the gas and it eventually came back to power. Never did it again, the guy i bought it from did run it almost completely out of gas, no external fuel filter to change though. My wife drove the jeep today, as soon as it started the check engine light came back on, she drove it the grocery no problems, when she got back i took it to the advance store, no problems ran great. Put the scanner on it o2 sensor, heater circuit, bank 1 same as the first time. By the way the heater core is disconnected, i didnt think that made a difference but i dont know for sure. Reset the computer. left the advance store, pulled out fine, hit 3rd gear stalled again, then after i pumped it several times, and took a sharp curve it cleared up and ran fine. the jeep has consistent 40-50 lbs oil pressure. so heres my thoughts. 1, needs new o2 sensor. 2. trash in the fuel lines, perhaps need to clean injectors. 3. catalytic convertor stopped up. The check engine light does not come back on when it acts up. Can someone give me some feedback on this. am i on the right trail or is there something im missing. thanks chris

If I were to give any suggestion as an inexpensive experiment if nothing else. SEA-FOAM IT. By that I mean run some through it, the directions are right on the can of sea-foam. And when it says it will smoke (if you follow the directions exactly), they aren't kidding.

i poured some sefoam in the fuel, would you suggest direct application to the throttle body/ injectors?

Also, as an experiment. I've heard you can unplug the O2 sensor and see if it continues to act up. If it runs fine after it's unplugged, you should have the problem located and can replace it.

i poured some sefoam in the fuel, would you suggest direct application to the throttle body/ injectors?
If it were mine, I would.
But BE CAREFUL, do not put in too much at once, as it can hydrolock!!! Follow the directions.
Consider unplugging the o2 for an experiment.

can the o2 sensor cause this problem? Am i right in assuming when you reset the code the computer defaults to the standard calibrations for the system? If the o2 is bad it could be sending the wrong message to the engine, ie less fuel or more fuel right?

Ive run the stuff, amazing!

can the o2 sensor cause this problem? Am i right in assuming when you reset the code the computer defaults to the standard calibrations for the system? If the o2 is bad it could be sending the wrong message to the engine, ie less fuel or more fuel right?

Yup -- I'm not sure on the older Jeeps, but (in general) if you have an O2 heater fault, the O2 sensor will take a looong time to heat up (waiting for the exhaust to heat up the sensor). If you set the fault during the trip, you'll go into sensor limpin and the ECU will ignore the sensor (it'll drive more or less OK). But if you start the car after being at the store a short time, etc. the sensor is still "partially" warm. Drive down the road and the ECU starts using the sensor to control fuel. When it cools down, the sensor lies to you and it drives like crap.

Unplug the O2 sensor completely and you'll force it to be in limpin all the time. It "should" drive more or less OK once it warms up a bit. BUT -- before you replace the O2 sensor, you'll want to check the wiring to make sure the power and ground are OK to the O2 sensor heater. If I recall correctly, Jeep uses a relay to "hot-wire" the O2 heaters. YOu could just have a bad relay or wiring.

Sorry for the delay:o.....TMessick answered your question though.


If it were mine, I'd do the Seafoam trick, then move to the O2 sensor unplugging experiment.

I'd dig up the factory manual and go through the troubleshooting procedure for the codes you are seeing. You can spend a lot time chasing your tail by trying to guess at how to troubleshoot what the PCM is telling you.

The obd2 code was for upstream o2 sensor heater circuit. I went ahead and bought an o2 sensor, havnt had a chance to drive it since. Thanks TMessick, i just couldnt put my finger on why it did it right after i reset the code and didnt do it when the check engine light was on. thanks chris