Thanks for posting the specs on that sensor, I've got a similar problem I'm t-shooting right now... Have heard of guys using those handheld infra-red thermometers for measuring coolant temps... point it a spot on the engine that is likely to be in close contact with the coolant, i.e. the thermostat housing... I'm gonna try it myself and see how the correlation is. Also wondering if you can access the wires for the sensor at some point in the wiring harness that doesn't require being a contortionist...

Anyone know if there is a practical diagnostic for the aux air valve ?

Also... I'm wondering if there is any reason that the aux air valve couldn't be re-located. The "other" end of the two hoses is very accessible, couldn't one simply cut the old hoses off and abandon the original valve, run two new hoses to the new valve, mount the new valve say on the firewall near the charcoal canister or some such, and extend the wire harness to reach the new valve ? Does it really _NEED_ to be where it is ?

edit: almost forgot... when you pull a vacuum line, won't the O2 sensor pick up on the change in the exhaust stream, and signal the ECM that something changed, which in turn will cause a mixture change ??? It's a "closed loop" right ???

Thanks,
Jeff