Testing the Coolant Temp Sensor?
 

All,

A friend of mine is having problems with his MY97 Legacy (US spec Legacy L, Automatic, 160k miles). Basically poor fuel economy and sluggish performance. He took it to a shop a few months back and they ran the codes (not recorded or given to my friend), removed the cat, did some testing and announced that he needed a new MAF. Installing a used MAF from a junkyard did not resolve the issue.

Based on what I've read on this fine site, I instructed him to pull the MAF connector whilst the car was idling. The engine stalled and died, which I interpret as indicating the MAF is good.

I've forwarded him the links from Saxonfields about checking the blink codes and he intends to perform the tests this weekend.

He's got a host of other issues that may be contributing to the issue (plug wires have never been changed, plugs last changed about 50k ago, etc) so I suspect that replacement of some parts is in order to re-establish a baseline.

But, given that it plays a role in determining the Air/Fuel mixture, I want him to test the coolant temperature sensor. Are there any procedures for testing the Coolant Temp Sensor to make sure it is good? How about the Oxygen sensor?

TIA,

Scott