# Power and MPG loss when cold?



## Mark17jettaS (Jan 17, 2017)

I noticed today was the first sub-30 degree day, and my MPG went down from 40+ to struggle to get near 30MPG. I also felt that the car was a bit sluggish. I am stage 1 Uni, and thought that maybe it was a safety measure that the car ran rich when it's very cold outside. I experimented by getting on it a few times on the highway, and suddenly it woke back up and went to 40+ mpg and better power. I was driving 240 miles today for work, so this whole cycle happened a couple times. I've been tuned for 2 weeks, and last winter I didn't notice this happening. Does anyone have a guess what could be happening? losing power and 10+ MPG? No CEL's either.

EDIT - I DID notice a few MPG's better when I was tuned. It was VERY easy to get upwards of 45+ mpg. Today, I could barely hit 30MPG coasting.


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## Chockomon (Aug 20, 2005)

*FV-QR*

i wouldn't judge fuel economy from the MFD - instead, keep track of it by filling up and dividing the miles driven by the amount of fuel used.

It's likely that the ECU detects that it is cold out and runs rich to compensate


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## Stephane_jetta_2017 (Oct 18, 2017)

Question, do you let the idle goes under 1000rpm better using the car when it's cold?
I am in Quebec last week we were at -5C and the difference in fuel consumption even with snow tires was not so important.


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## Mark17jettaS (Jan 17, 2017)

Yes, I generally let the car warm up until the revs come down. This phenomenon was occurring after the car was operating for 20+ minutes. It had much less power (felt like pre-tune). Since it warmed back over 35 degrees, it's been fine. perhaps one of the sensors was a little shocked at the change in temperature overnight and got stuck on the "rich" warm-up setting. Sometimes blowing the "farts" out of the car on the highway seems to reset it, and it goes back to normal. I'll keep you posted. If it is in fact protecting the car, I'm appreciative.


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## Stephane_jetta_2017 (Oct 18, 2017)

Mark17jettaS said:


> Yes, I generally let the car warm up until the revs come down. This phenomenon was occurring after the car was operating for 20+ minutes. It had much less power (felt like pre-tune). Since it warmed back over 35 degrees, it's been fine. perhaps one of the sensors was a little shocked at the change in temperature overnight and got stuck on the "rich" warm-up setting. Sometimes blowing the "farts" out of the car on the highway seems to reset it, and it goes back to normal. I'll keep you posted. If it is in fact protecting the car, I'm appreciative.


what is making the difference is the electrical device ON, fan, rear defrost, light, etc...


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