Running Rich? Tahoe help/Computer Reset

[GoodmanOX]

Hey guys. My 99 OBS Tahoe is running rich, I think. The exhaust smells like it, and the MPG is terrible. Also, it feels like it's stuck in a lower gear; it won't coast. What could this be? How do I reset the fuel trim levels/ computer without a scan tool?

[blueflamed03]

disconnect battery, let sit for about 5-10 minutes, and re-attach cable.

[bai78]

Have you scanned for codes? When was the last time you changed the o2 sensors? You could be running rich due to a bad o2 sensor (before the cat) which is keeping you in open loop versus closed loop.

It's a possibility worth exploring. Also, that would be a contributing factor to the LTFT's.