Oxygen sensor problem

[pscheat]

1040659

I've got an "interesting" problem with my 97 Jeep cherokee - 4.oL engine. The infamous check engine light came on - with codes indicating a problem in the oxygen sensor circuit. My mechanic replaced the rear sensor (twice - but that's a long story) but the Check Engine Light is still coming on. When he resets the codes and monitors the voltages out of the sensors, everything appears to working properly. Then later, always after leaving the shop, the light comes on. And it always apperas to come on after the second start once the codes have been reset. Any thoughts on where to look.



Thanks[addsig]

 

[balloo93]

1040714

I may be way off base with this, but here goes: I'm pretty sure that your O2 reads exaust gases for burned to unburned fuel. Such as running lean or too rich. Besides the obvious advice like check all your wiring for frayed or burnt areas. The first thing I would do is clean your throttle body out with some carb cleaner, run some injector cleaner (buy the GOOD stuff) in the fuel tank, and check your plugs and wires. If you read my other replies you'll see how fixated I am on spark plugs. Check each one seperately to see if the combustion is rich or lean (rich will smell like gas and lean will be white and burnt looking). Autozone has replacement wires for around $15, and I would go with what plugs the manufacturer recommends. Just because it cost more does not necessarily mean it is better.



I haven't played with mine enough yet to know where the mass air is, but you should also consider CAREFULLY cleaning the sensor (with a Q-tip and some alcohol). If it isn't any of those check for exhaust leaks around or on the manifold.



Long winded....yes. Effective......maybe.[addsig]