[Mk2] [Turbo] Would failing thermostat make car run rich??

[joemacmr2]

Trying to find out if I have a bad thermostat/temp sensor/temp gauge sender. Car is running rich as well ( tail pipes black, spark plugs sooted after 600 miles ). I have found that my gauge rarely reaches the 'just below half way mark'. Most of the time it would be closer to quarter but does reach around half way in warmer weather.

Not sure if it is reaching normal temp and my sender to dash is bad. I will try this first. (Wiring/gauge is good as it flicks to hot when I ground sender wire)

Failing that I will change thermostat.

I get a lot of exhaust popping (excess fuel)but put this down to exhaust and decat

What's your thoughts??

[toxo]

If your dash gauge is not getting up high enough, thermostat. It's possible the dash temp sender has failed, but unlikely given previous members experience, I would say! Get the stat done, it doesn't cost much for a proper Toyota one (don't use a blueprint one) and it's an easy job.

It is likely the thermostat is either stuck partially open, or the spring has got weak over time and is opening too early. This means all your coolant circulates via the radiator when it's not hot enough to need cooling down, over-cools, and thus doesn't warm up as it should.

The gauge on the dash should reach just below half way within 5 minutes of starting the car.

[joemacmr2]

i have a sender here to put in, £7 so i thought why not. wishful thinking lol
in this weather it would take about 15-20 mins to reach half way (on the rare occasions it does). from memory during the winter it never reached half way, always just above quarter .

If it was the thermostat, would this make my car run excessively rich with ecu still in 'warm up' mode?

i was shocked how carbed up my plugs were after 600 miles

[ej2_sir]

Yes it will run rich and will run badly. Generally the MR2s are absolutely painted at half way on the gauge after approx. 5 - 10 mins so as above, get that stat changed!

[joemacmr2]

was just working out my mpg for town driving (60 miles for £20 super) so works out around 19.5 mpg and thats taking it handy eough for 50 out of the 60 miles. does that sound bad?