Really Terrible Gas Mileage

[robm]

1993 Loyale, 350,000 km close enough.

 

Recently, I have been getting really terrible gas mileage. Less than 400 km to a tank, that is like 19 MPG! Even highway miles don't improve it much.

 

The original t-stat got stuck open in the winter, and the only way I could get the engine up to temperature was by blocking the rad with cardboard. I made an 800 mile trip like that just after Christmas, got decent mileage (30- 31) even with the cold weather, snow, etc.

 

In January, I got a new T-stat. It is made by Tama (OEM). The engine now gets up to temperature without the cardboard, the temp. gauge sits where it always has, but the gas mileage has taken a dive.

 

I suspect this is may be due to moving the wiring on the CTS, which is right in the way when replacing the T-stat. I have read the accounts of the corroded wiring, etc. Could this be the problem?

 

Is the problem on the sensor side of the connector, or the other side? I had a look at the non-sensor side wiring. It all looked to be in good condition. Is the corrosion something that is visible from outside, or is it buried deep in the wire, under insulation?

 

No codes. But I did get a chance to learn how to read and clear them, playing around with the connectors. I provoked a CEL by unplugging both the sensor and the purge solenoid, but they cleared when plugged back in.

 

Any good ideas on how to fix this? I have to make that 800 mile trip again soon, and gas is $5 a gallon around here.