HALP!! My 86 GT H20 Temp Low, & Fuel Consumption High--

[Jonathan Monetti <jmonetti@us.net>]

Hi All, 

I've got a problem, and it's driving my a little crazy.  

My 86 GT was running VERY cold--H20 was at the bottom two pegs of the
digital guage.  Naturally, fuel consumption was very high, as the computer
was keeping the fuel mixture rich for a perceived permanent cold start
situation.  So, getting 12 MPG wasn't a shock to me, knowing I had to
replace the thermostat.  

I replaced the thermostat.  Car warmed up a little. (very little).
Mileage went up to 14-15 MPG.  Then I noticed a tiny leak in the radiator
(orig--and mighty crusty).  So, I had to opt for a new aftermarket one at
$300 (dealer wanted
$800 for stock rad!!).  Installed the new rad, and...the temp went back
down.  Now I was getting 8-10 MPG.  

So, I test the thermo-time switch and it *seems* OK (I wont be comfortable
untli its replaced).  I tested the cold-start valve, and it didn't give my
any fuel--car was too warm, but I could see it wasn;t leaking or damaged.  

So I disconnected the lead to the cold start valve, and a test drive
produced 15-20 MPG!!  OK, I've found my problem, right?  Well, I'm not
sure.  The car still runs very very cool, and I'm not so sure where the
problem lies.  

Bad temp-sensor/sending unit?  Thermo-time switch?  Cold Start valve?
Trip computer? I
can see the MPG getting better without the CSValve connected, but the low
temp still has me baffled, and MPG still isn't optimal.  I feel the temp
sensor might be OK, because it
read a couple of brief spikes (nothing high enough to be dangerous) while
I was filling the system & while the
thermostat was opening up.
 

What do you all think?  I think the previous owner probably treated the
coolant system for the radiator leak, so could that have the effect of
*lowering* the overall operating temperature?  

Losing my marbles, 

Jonathan Monetti
86 Coupe GT, 82k