Gs300 Idles High When First Started In The Morning

viclykewhoa · June 20, 2006

Hi all,

I have a 1999 GS300 and the car idles rather high when I first start it in the morning after it has sat over night. The car idles at about 1700 RPM and then drops to about 1100-1200 after a minute or so.

Also, as of recent, my check engine light came on and the same code I've been having problems with emerged: P0125. My engine coolant temperature sensor has been changed as well as my oxygen sensor (Bank 1 Sensor 1, which was giving no reading on the OBDII scanner) as recommended by SK towards the end of the last summer. Changing my engine coolant temperature sensor had no affect on the CEL but changing the O2 sensor solved the problem.

Now that the code has resurface, it looks like I might have to replace my thermostat . My mechanic friend said that it could be because I have a thermostat rated at 190. So, I should change it to an all season rated thermostat of 180. Seeing how the two times the CEL came on with this code was in the heat of the summer, I believe the thermostat is the likely cause this time around. Changing the O2 sensor last time along with the cooling weather (due to the timing of when this was done) turned the CEL off. Now that it's getting hot, though, I think the thermostat is acting up again and must be replaced.

Let me know what you guys think. Is the thermostat the likely culprit? I appreciate any thoughts.

SK, this code sucks...

Here is the DTC definition for your convenience:

Diagnostic Trouble Code (DTC) p0125

DTC Definition: Clsd Loop Fuel Ctrl Insufficient Coolant Temp

I got this definition from http://www.actron.com/code_lookup.php, which was posted on a much earlier topic in this forum.

Kangaroodent · June 20, 2006

The car has to be driven or at least revved to a few thousand rpm for a couple minutes in order for it to get at the proper idle speed, but unless it's really damn cold, 1100 seems a tad high indeed.