My gas mileage is terrible, somewhere around the 17 mpg range city and I never ever broke over 20 even on highway driving. It is a 79 n/a 5 speed car.


I have new plugs, wires, cap and rotor, and I always use good gas. The guage never reads over 140-160 even in traffic. i installed a new factory spec 180 degree thermostat but the guage still reads cool. I'm starting to suspect the temp sending unit may also cause the car to run too rich by giving an inaccurate reading.


I looked by the thermostat housing but the darn thing has like 4 sensors sticking out of it. which one sends the signal to the computer to adjust air/fuel mixture?


Also, I even tried putting a piece of posterboard over the radiator but the darn thing just won't read where its supposed to. Please help!

 

Since there is no actual middle temp mark, where does the needle rest relative to the F in the center of the temp gauge?

 

It rests just inside the inner set of marks, supposedly in the "good range." But it never even creeps past that mark though, except when the motor is shut off for a little while and started back up. I suspect this is because of the cooling fan not running when the motor is off. When I start it up when the heat soak has occurred, even sitting at home idling the temp guage goes back down. Again, I suspect this is because of the fan. It is the stock type fan with no shroud and the viscous drive still works; it has not locked and still freewheels.

 

Check your antifreeze. If the mixture has too much antifreeze and too little water, it can cause the engine to not reach normal temp. You haven't, by chance, used any additives, such as Water Wetter, or anything like that, have you?

 

To me it still sounds like a stuck thermostat. You said you replaced it... if you can't figure anything else out, I'd replace it with a different one. 180 deg is fine. They're only $5

 

maybe replace your water temp sensor on the thermostat housing that worked for me. they are like $10 or $15

 

I just replaced it yesterday and it still had the same fault. When I took the old one off, it actually wasn't stuck open, it functions normally. I think I'll take Zbabe's advice and change the coolant as a precautionary measure. It can stand to be changed