What are the symptoms of a bad water temp sensor? From what I've read in searches this seems to be my problem.

Ever since it started getting cold my car is very hard to start (the colder it is the more times it takes to start). Generally it will turn over, run for 1 second, and stall. Unflooding the car (s5 t2, no emissions btw) doesn't seem to have any effect on getting it to not stall. I don't smell gasoline as if the car was flooded.

The car will run rough up to 3000rpm (stutter) then as soon as it hits 3000rpm its as if nothing was wrong. It continues to stutter below 3000-3500rpm until the car is warm, and then it runs perfectly, idles perfectly and you'd never tell it has this problem.

So far I've tried:
New 02 sensor
New fuel filter
Fresh spark plugs (stock heat range)
Reset timing while the car was warm to dead-on stock timing.
Replaced battery and terminals.
Injectors cleaned about 10 months ago.

My theory is that the water temp sensor is telling the ECU that the car is already hot and the ECU is not adjusting fuel trim for the extremely cold temperature (should be adding extra fuel).

Am I close or am I way off base here?

 

hmmm I believe though that the default for the ECU would not be be full hot....

You may just have a 7 that is pissed of because you're winter beating its ***...

I think that if your ECU water temp sensor is either not present or sending a faulty signal - the ECU defalts to 60 or 70 degrees....from what I recall....

Do you/Have you put gas line anti-freeze in the car at all? BTW how cold is it there - are we talking ACTUAL winter or texas winter....

 

Baltimore winter 14-25 degrees in the morning, 35 during the day (sometimes 40)

No gasline antifreeze

Edit: I take it as two signs, 1. Haltech. 2. Move to florida, screw the cold.

 

its probably just in a pissy mood from the cold air

I mean if the car runs mint when its warm...and ran and started fine when it was warm outside - unless you have had a major failure - it should still be in the same shape...I say get an inline block heater...

or you could just erect a 60' by 80' heated garage for your pet...hehe

 

Yeah I've really been looking in to a block heater. I think it would definatly solve the problem and keep me from freezin the boys off at 7am on my way to work.