180* stat is not going to hurt your mileage a significant amount. you most likely got a bad stat. when I had my 2000 5.9 I took a step back to a 195 stat and did not see enough of an improvement in mileage to justify keeping it in. I went back to a 180* stat and was much happier.

a 160* stat will keep it in open loop mode.

 

Keep it in open loop? Wow, talk about "ouch" in the MPGs.

Steve, can you explain that a little better, just for my curiosity? How does the coolant temperature affect the oxygen sensor temperature? Or does the computer have to have both the O2 sensors AND the engine temp reach a certain degree number before it goes to closed loop?

 

4 wire o2's have their own heaters to get them up to op temp quick. newer trucks (at least 2000 or newer as mine had this) have fuses on them. if they blow (because of a shorted wire like mine did 1x) then it will run funny and inconsistent.

back to the o2's... they do not need to reach any specific temp... (have their own heaters).

the comp will use all of the input sensors that it has to determine how to run the motor... if the coolant temp is cold but intake air is hot, it will run it accordingly (determined I presume by the pinhead engineers at DC) so that it will provide smooth operation during warmup. they may also bump the idle some (not remember exactly it's been a few years since I had the 2000) to help with the warmup process.

my '05 diesel has a feature that if the ambient air is below a certain temp 30* or below (not 100% sure what the temp is) it will kick up the idle to help warm up times.

 

Im running a 160, have been for a few months now, I havent noticed any real problems , expect for when its at temp (160) truck seems to run more sluggish then when it is ice cold. Aka , Delayed response, poor performance, Im going back to the 195 stat next weekend when i get my paycheck, at the same time im modding that housing and cutting that stupid tab off.

 

Do you know if that fuse is in the fuse block, or part of the wiring of the O2 sensor? (Sorry, my computer with the FSM on it is at work. )

Thx,
Cartman

 

what do you mean modding that housing and cutting that stupid tab off

 

theres a stupid tab that has the part number stamped on it, but it makes removing it a bitch , because it wont pass the accesory bracket without saying a few curse words and ten mins of wiggling it. Im going to cut it off, ive been meaning to , the 3 times ive had it off lol. Also while im there im replacing the snap clamp with a regular screw on hose clamp so the next time im in there , i wont be cursing.

 

Surprised to see so many people have issues with the 180 stat. Planned on doing it in the near future, might hold off now.

 

yea i planned on doing it as well...idk if i want to now. guess i could always try...and see what it gets me. i just hate draining everything and having a huge mess

 

Note that when the housing is installed that it is slightly bent to point to the front of the truck. I inadvertently installed my backwards at one time while changing out the t-stat and thought I was creating an air pocket that lead to running hot.