O2 Sensor help

My check engine light has been coming on and off randomly for the past month. I am pretty sure it's an oxygen sensor. Sometimes it starts and idles ruff and other times it will run fine but when it's shut off for 30-45 minutes and then restarted it runs rough.

My question is: how do I tell which of the four sensors to replace?

I probably should just replace all four while I am at it but didn't know if the upstreams sensors were usually the ones to go before downstreams or vice versa.

TIA

Go get a OBD2 scanner from auto zone (rent). It should specify which is bad if that is the case.

242_cherokee said:

Go get a OBD2 scanner from auto zone (rent). It should specify which is bad if that is the case.

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My buddy had one and I believe it said number 4. I don't know which one that is, does anyone know how they are labeled/numbered?

TIA

I believe that would be front to rear.

The only way to be sure what the problem may be is to get the CEL codes download and either Google the code number or post it here.

Are you sure that it's not the #3 injector misfire code? I got that one quite often after letting it sit for 10-20 minutes and then restarting. There's a TSB out there on it. I think the jist of it is that the fuel left over in the injector actually vaporizes due to heat soak issues from the exhaust manifold in the #3 cylinder area. It will run rough on a restart for about 30 sec to a minute and then it will be fine. The fix is to wrap the injector with a bunch of high temp insulator.

Definitely get the actual code before you start throwing money at it. The rear sensors are just there to check the cat converter and will not affect the engine running.