Caveat: I know nothing about mechanical stuff/cars in general.

I bought my first Blazer about 2 weeks back (2002 LS 4dr, 4wd, Auto), and am trying to learn as much as possible about it. To that end, I also got an OBDLink from Scantool.net, and used that to check a few things.

I am concerned that my truck might be running too cold. I had the OBDLink plugged in on my drive to work today (about 5 miles), and the Coolant Temperature reading peaked at 177F/82C. Intake Air Temperature peaked around 102F/39C.

Fuel System 1 Status/Fuel System 2 Status both showed "Closed Loop". If I understand what I have been reading correctly, Closed Loop uses more fuel then Open Loop.

Before purchasing, I had the dealer flush the existing coolant, and they have replaced with some generic green stuff.

So, to sum up, my questions are:

What temperature should I be running at?
Why would I want to be in "Closed Loop", especially if it uses more fuel?
What can I do to get the truck running where it is supposed to be?

 

It is running cold. Good running temp for these is around 180*-190*

Closed loop is basically to allow the vehicle to get to running temp faster. And thus keeps the RPMs up to let the engine warm up. You don't really want to be in closed loop for any reason other than that. And you are in closed loop because the computer is getting a cold engine reading.

Do you have any diagnostic codes? Check engine Light on? Leaks?

 

I did have a Check Engine Light on, but I cleared it with my new OBDLink toy... I am getting DTC P0155 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1).

No leaks that I have been able to find.

 

Maybe take it out for a longer trip. 5 miles may not have been long enough for it to get to operating temp.

Plus the O2 sensor may make your gas mileage suffer.

 

I run about 185-200 AT MAX!, with my new radiator it might rise up to 210, but once it hits the stock thermo temp... it drops, FAST, and stays cool.... and thats after 1 hour plus trips...

 

Uhmmm...I believe zdarto is mistaken.
Open loop is when the vehicle operates in pre-dermined set values until the vehicle warms up. Once it reaches temp, the computer uses input form all the sensors to set the fuel mixture, timing, idle etc.... This is called closed loop and is the most efficient mode.

Your vehicle can also operate in open loop if the check engine light is on.

 

So I am back to front, and Closed Loop is where I want to be?
Do I need to be worried about temperature then?

 

Yes, closed loop is where you want to be....once the Blazer has warmed up.

I believe the book calls for a 195* thermostat. Your 177* doesn't seem that out of line depending on outside temperature and how far you drove. One other possibility is to check your fan clutch. If sticking it will pull a lot of air through the radiator and keep things cool. I believe your computer would illuminate the check engine light if your coolant temp runs too cool, or takes too long to warm up.