Question regarding thermostat

[floydr007]

Hey everyone, i just wanted to post this as a heads up. The night before a long trip, my 99' sport (SOHC) started idling extremely high out of the blue (around 1100-1500 rpm). There were no other symptoms that I noted, however i was not driving it far at all. I reset the computer, and it didnt do anything to fix it. The next day, about an hour into my trip, my thermostat failed and my car began overheating. Thank god i read on here to crank on the heat to cool down the engine, it worked wonders. Luckily, i caught the overheating before any damage could be done to warp the heads. So, sure enough the thermostat failed, and i needed to get it replaced, a simple and cheap fix. Since the installation of the new thermostat, my idle has been back to perfectly normal. So heres my question, why would the idle be affected by the failing thermostat and overheating condition?

 

[BrooklynBay]

The ECT sensor changes the mixture in proportion to temperature.

 

[BrooklynBay]

Refer to the following chart:
Dead Link Removed

 

[MONMIX]

^^^ Yikes WOW !!!!!

Nice chart B.B.

Just to dumb it down for any other readers if it gets hot the computer makes the motor run faster so the fan moves more air

 

[gijoecam]

^^^ Yikes WOW !!!!!

Nice chart B.B.

Just to dumb it down for any other readers if it gets hot the computer makes the motor run faster so the fan moves more air

Indeed. It just bumps the idle up and adjusts the shifting strategy in an attempt to accelerate the cooling.

-Joe

 

[floydr007]

Thanks guys, thats really interesting. I was just surprised because my temp needle never showed anything off the wall when the idle shot up (the gauge must be pretty unaccurate). The idle is obviously back to normal now though with the new thermostat.