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Discussion Starter #1
Hey folks. First time caller... long time listener.
My lovely 2003 Jetta 1.8T is sucking back gas like mad and has been since I bought it in 2007.
I use it mainly for city driving and maintain the car fairly well. Regular oil changes (synthetic), premium gas, new timing belt, etc and drive conservatively.
According to the sticker, the "new" 2003 1.8T had the following fuel economy:
City: 22mpg / 10.7L/100km
Hwy: 29mpg / 8.1L/100km
With simple city driving in normal weather I have rarely seen 350kms/217miles per tank. I should get around 475km/325miles per tank, give or take some miles due to aging.
What should I have my mechanic look at when I take it to the shop next week?
Thanks,
K.
 

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Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (kellytmoney)

Are you running rich?
*Scan for DTCs
*Inspect O2 sensor readings via VAGcom - Block 032
*Inspect MAF
*Inspect for boost leaks
*Inspect spark plugs
 

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Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (kellytmoney)

Are you chipped and how heavy is your foot? If I stay out of the turbo I get pretty close to the sticker numbers, but if I use lots of boost my numbers become horrible...like yours.
I lost a few MPG when I got chipped, but not too much. I also lose a few more MPG with the $hit Ethanol blend I have to put in the tank.
 

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Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (emspilot)

Quote, originally posted by emspilot »
Are you chipped and how heavy is your foot? If I stay out of the turbo I get pretty close to the sticker numbers, but if I use lots of boost my numbers become horrible...like yours.
I lost a few MPG when I got chipped, but not too much. I also lose a few more MPG with the $hit Ethanol blend I have to put in the tank.

I get into boost all the time and drive it pretty hard, and I get about 26-27mpg. And most people would say a chip helps with mpg. OP, something is pretty wrong, but idk what it'd be. Hopefully something easy and cheap.
 

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Discussion Starter #5
Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (McBee)

Thanks for the advice.
It is possible that I am running rich. There is the slight smell of petrol after ignition when I head to work in the morning, but nothing afterwards. But what do I know. I'm just a "driver".

I will have it checked out.
K.
 

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Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (emspilot)

I have not done any mods myself, but who knows if the original owner sneaked something in there. It doesn't feel more powerful than the other 1.8T's I have driven (Passat, A4).
I am not a heavy foot and only use boost when I am on the highway, which is rare.
 

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Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (kellytmoney)

Quote, originally posted by kellytmoney »
Thanks for the advice.
It is possible that I am running rich. There is the slight smell of petrol after ignition when I head to work in the morning, but nothing afterwards. But what do I know. I'm just a "driver".

I will have it checked out.
K.

It's typical to run more rich on cold starts for the warm-up phase.
When you take it to the mechanic have him/her check for the fuel trims when the motor is warm. That will verify whether you are running rich. And if you are, the next step is finding out why.
 

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FV-QR

Quote, originally posted by beaker420 »
bone stock 1.8t and i get 350 in the winter and 450 in the summer

I love when I fill up with summer gas for the first time in the season. Seems like it lasts forever.
 

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Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (kellytmoney)

I have been having this same issue with my 02 1.8T. Through some quick searches I have narrowed it down to a couple things. As the OP said, boost/vac leaks, fuel filter or the front 02 sensor- all this is considering you have a good running condition and up to date maint. I'll be looking into mine soon. Good luck.
 

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Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (kellytmoney)

Any unusual wear on your tires? Had a 4 wheel alignment lately?
Just some other things to check...
 

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Re: Horrible Fuel Economy - 2003 Jetta 1.8T Wolfsburg (kellytmoney)

clean your maf,check plugs...
 

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Ensure that your tire pressure is adequate.
Youd want your parking brake off too.
A/C and defrost will lower MPG i think.
Make sure that the engine says TDI on it too. this will help
 
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