Running pig rich

[135sohc]

25 miles per gallon, tail-pipe is black sooty like a diesel, pulled the plugs and they were black as well. Code 17 for running cold. 2.2 tbi 251k

Dropped a new t-stat in as well as a new oem CTS. Nothing to outright indicate they were bad but I had them around already so... Plugs are stock RN12YC champions. New denso oxy sensor going in tomorrow as I suspect the bosch unit has gone bad again. But with age and mileage on the SBEC coupled with in the past I have borrowed a DRB and could not access alot of the data... I'm starting to lean towards a possibly defective computer. One minute it will idle @ 1900 rpm and the next it will be 1000 with zero pattern or consistency. There are no vac leaks, the IAC is clean and free of crud.

I'd just like this damn thing to run right and consistently. Wasting alot time trouble shooting it, testing components, replacing suspect items and its still out to lunch 98% of the time. Theres got to be something stupidly simple I keep overlooking :confused2:

[bakes]

Try a spare coolant sensor might have gone bad and not set a code.

[cordes]

If the new sensors don't fix it I would look into the wiring.

[shadow88]

With the searching idle, and the coolant related codes, I would lean towards an air pocket possibly caused by improper bleeding, or a leaking head gasket / cracked head.

If you changed the t-stat, coolant sensor, and O2, Sounds like you're on the right track, but I'd block test or run with the rad cap off and watch for bubbles.