This is probably a dumb question, but does the temp sensor reading affect whether or not ECU tells the system to run rich? I'm talking specifically about the sensor that produces the temperature reading in the dash. For example, if it was completely unhooked or for whatever reason always read super low, would the carb run rich all the time? I'm just curious...

Along those lines, where do most of you see the temp at in the dash? I used to be 50-66% up, replaced the thermostat, and now it always seems to be 20% or so. Thanks!

This is specifically on a Gen I. Thanks!

I dont think the temp sensor has anything to do with gas unlike the o2 sensor.

The temp sensor that you're referring to is actually a sender. No it won't effect ECU fuel mixture command. The CTS (coolant temp sensor) will, however. The sensor comes out toward you from the water outlet with 2 pins, whereas the sender goes up with one wire.

Thanks for the info guys, I appreciate it! Just getting ready to try to re-do an emissions test and wanting make sure I've thought through all the bugaboos!

By 50-60% I would guess you mean in the middle (or so) of the gauge? Ether way 20% sounds low and can lead to problems, ie; engine can't get up to operating temp and it will run rich.
do a google on engine not warming up.

I think you can remove the rad. cap and watch to see if the coolant is circulating when the engine is still cold. That would indicate a stuck open thermostat, crazier things have happened.

If the 20% range is normal then carry on!!
Maybe someone should answer that one...

20-25% of gauge seems to be normal; my oil temp gauge reads about 180 degrees in that range. Probably some variation in those OE water temp gauges though.

Every car I've ever had had the temp gauge right about 50% when they were running correctly. I'd say he either has an engine that isn't getting up to the correct operating temp, which would effect the air/fuel mix, or he's got a faulty temp sender, which would not.

A 180?f T stat runs under 1/4 on my 87, a 190?f is about 30% during cool weather.

Most will get to 1/2 on the gauge during hot weather. The thermostat opens over a temperature range so it may be cracking open at 190? and fully open at 212? (from what I measuread a few years ago).

If your new thermostat is a cooler one that what you took out you will lose some fuel efficancy. Heavy duty thermostats do seem to work better and more consistantly, I have had problems with the inexpensive ones, Stant HD seems good.

Kevin C

Does your fuel gauge read at or below F when filled all the way up? Do you still have a ton of fuel at E? If so, both your fuel gauge and temp gauge are reading low. There's a voltage limiter in the circuit for those gauges, and if it loses it's ground (a screw on the back of the panel PC board), the gauges see full batt. voltage and permanently warp the bimetals inside that move the needle, causing a low reading on both. Taking the gauges apart to "unwarp" the bimetals with brute force causes the age brittle needles to fall into many pieces. Any glue you use to put the needles back together ruins the weight balance of the needles on the counterpoise spring. You buy a 5gal can of fuel for "lack of fuel gauge" events. A calibrated stick comes in handy, to poke down the filler hose and check the fuel level. Steam from under the hood is a reliable indicator of engine overheat. Who cares if the engine is cold?

Damned good thought, Eddy - even if it proves to not be the cause. The same think can happen if the voltage regulator doesn't clamp the alternator output and allows a spike.... even if only for a few seconds.

Frank