Most people with fieros complain about their cars overheating at some point or another but we have the opposite problem. The car wont heat up! We have been through 2 thermostats with no success. Dad put a thermocouple on the motor last night and the temperature never went above 120 degrees. Needless to say the motor is running rich and the computer still thinks the enigne is cold. What could be causing this?

How did you test, how long run, was it driven? Did this just happen?

Is he putting the same brand of stat in each time. If so get a different brand and speed the $ for a good one. Don't buy the cheaper house brands.
I've had the same problem happen twice and it was the stat both times.
The stats must float open from the water pressure. If you test them in hot water they test good but don't work in the car.

Replacing the stat with a good brand has always fixed mine. In my GrandPrix one only lasted a year and started doing it again. Of course the stat only had a one year warrenty.

Also when putting the stat in be sure it's seated all the way. If not you run the risk of bending the metal arms when putting the cap back on.
The stat has to seat flat in the housing. Might also feel and make sure there in not an old o-ring left stuck in the ridge at the bottom of the housing.

[This message has been edited by Dodgerunner (edited 10-09-2007).]

quote Originally posted by Dodgerunner: Also when putting the stat in be sure it's seated all the way. If not you run the risk of bending the metal arms when putting the cap back on. The stat has to seat flat in the housing. Might also feel and make sure there in not an old o-ring left stuck in the ridge at the bottom of the housing.

Exactly.
I needed to clean up my housing with a scotch-brite pad, used light grease on both the housing and thermostat o-ring and gently worked it all the way down into the housing.

Ill check into that. Thanks Guys.

PLEASE the name of any thermostat that will make my fiero run cold!? I want it to run colder than my ex wifes lawyers heart

Im thinking that your gage is bad or the scensore\ground for the gage is bad.

quote Originally posted by James Bond 007: Im thinking that your gage is bad or the scensore\ground for the gage is bad.

He tested the temp with a thermocouple so would guess he knows the correct temp other than the "guess it" gauge.

The existing thermostat is an OEM Delco 195 degree thermostat.

what temperature does the ECM go to closed loop mode and how can we tell if it is. Second, what temp is it suposed to come off of fast idle at?

Thanks

The ECM goes into closed loop as soon as it sees reliable readings from the O2 sensor, that can be in as little as two minutes from startup from my experience. It does this regardless of temperature, however, when the coolant temperature is below 160-170 degrees or thereabouts the ECM adds extra fuel because it assumes you need the cold enrichment. Idle is supposed to be normal almost immediately after starting, the idle speed is controlled entirely by the ECM.

The thermostat only operates as a bottom stop on the temperature range, the upper stop is controlled by the cooling fan switch temperature rating. A properly-functioning system is capable of keeping the coolant temperature at the thermostat rating in all but the hottest, hardest desert driving possible.

In your case, coolant has to be getting past the thermostat somehow in order to get to the radiator to be cooled. Do you have the heater hoses and core hooked up? It may be that if you don't there's enough pressure buildup from the water pump that coolant is just forcing the t-stat open while it's still too cold.

JazzMan

Closed loop also has a minimal temp, I believe it is 143 degrees. a fast o2 will be running at that point, and if the motor enters closed loop at that point, it will bog alot till it hits around 160.
As for the too cold, all the above suggestions. the only tstat I found that worked reliably at the correct temp was a failsafe branded one. the stant, autozone premium, delco ones all opened at 160-180 for me. the o ring not sealing is possible, but if the tstat is not seating all the way, you will see that trying to put the cap back on. the top flat of the handle will be flush to slightly below the top of the neck, you can check it with a straightedge. the better quality stats will have harder, thicker stainless arms on the handle that won't flex or collapse. check your old stats, the should not be bowed in at all, if they are they will bend in and allow the stat to unseat. The best way to verify temps and how the motor is running is building that aldl interface for a laptop or a pc with a serial port and hook it up and see what the temp the cts is reporting also. there are some links on the home page to how to b uild one if you can handle some simple soldering and fabricating. an older laptop that has a serial port works the best, there have been issues with the us serial adapters.
The mat in the air cleaner assembly can cuase rich running also, especially if disconnected or open. (open is infinate resistance, which sayin 0 degree air, which will cause enrichment.) but not cause cold running.

I fought this problem with my 86se, all stock cooling system, heater core and tb heater lines were all clean and perfect, and no tstat would get it over 160-170. car ran from 20k miles to 100k like that, never did fix it, used cardboard over the radiator to get heat in the winter. (I alos fooled the computer into thinking the temp was 195, was much easier than the continued parts replacing). tho now that I think of it, I wonder if the tstat housing was defective on that car, as it was like that apparently from the factory.