O2 sensor?

[outlawjoseywales]

1997 hardbody 4cyl. Today's misadventure:

I've had bad gas mileage and running problems. After checking and re-clicking my EVAP solenoid connector back on, I cranked her up and everything was great for about 15 minutes today. She ran great, I thought I'd solved the problem and all was right with the world. OH NO.

About 15 minutes, it started the same crap, not wanting to run, shutting off, blowing smoke, making crazy noises when it shuts off etc. Then the Service Engine Soon light started flashing, hadn't had that one.

I got an EVAP problem code earlier this week, but some has told me that it might be the O2 sensor. I've found there are two of them also.
Do I replace both?

Hope somebody can help me here.

[Q451990]

There is a diagnostic mode that you put the ECU in to check the function of the O2 sensor. Check out the factory service manual at http://www.nissanservicemanual.com

On page EC-31 it gives you a procedure to use to test the front sensor by changing the set screw on the ECU. The sensors do get sluggish, and can reduce MPGs, but I don't think they'll cause an issue like you're having.

In terms of which sensor to replace, typically just the front one. The back one is just a check to make sure the catalytic convertor is working properly, but it's not used for engine control like the front one.

The evap. canisters are sometimes a problem on these trucks. If messing with it fixed your issue for a while, it might be time to replace it. I'd go through the diagnostic steps on EC-20 of the FSM. I'd also look toward a dirty mass air flow sensor... I used to have a '97 hardbody, and it would very occasionally idle low. I sold it to my neighbor, and he mentioned that he occasionally has issues with it idling funny, and cleaning the MAF helps.

Good luck!

Heath

[outlawjoseywales]

Thanks for the tips. I'll give it a try.
OJW