2004 TDI wagon horrible fuel mileage

ron hughes · Mar 27, 2017

recently purchased a 2004 TDI wagon automatic. Its getting terrible fuel mileage. 24 mpg in town and 32 highway. I have owned many TDI's in my time and never ever seen mileage this poor. The car is showing zero codes from multiple readings. Cam lobes look almost new (car has 140,000 miles). Just had the injectors cleaned so that shouldn't be an issue. Turbo appears to be fine and the car has plenty of power. Got to get this car up in the 40's or it has to go. The car is virtually perfect in every way except mileage. Tires are at the right pressure. Thought the EGR might be the issue but reading are perfect. Helpppppp

VwPassion · Mar 27, 2017

ron hughes said:
recently purchased a 2004 TDI wagon automatic. Its getting terrible fuel mileage. 24 mpg in town and 32 highway. I have owned many TDI's in my time and never ever seen mileage this poor. The car is showing zero codes from multiple readings. Cam lobes look almost new (car has 140,000 miles). Just had the injectors cleaned so that shouldn't be an issue. Turbo appears to be fine and the car has plenty of power. Got to get this car up in the 40's or it has to go. The car is virtually perfect in every way except mileage. Tires are at the right pressure. Thought the EGR might be the issue but reading are perfect. Helpppppp

Hmm, the first it came up in mind... very very Very thick oil ???

ron hughes · Mar 27, 2017

The oil is the VW oil. Always changed at VW. Additionally, we had a compression check done and all cylinders were well within a pound of spec.

scottw99 · Mar 27, 2017

Brakes hanging? Alignment? Thermostat?

ron hughes · Mar 27, 2017

recent alignment. car is not running hot or cold just right. Not sure about the brakes.

scottw99 · Mar 27, 2017

Have you confirmed the temps via diagnostics tools or is this referencing the dash?

Jack up the wheels one by one and see if the brakes are hanging, the rears might be more likely.

ron hughes · Mar 27, 2017

the car has been completely diagnosed by both VW dealership and a local VW shop. The car is completely in spec in every way. No codes nothing. The only thing that has not been done to the car .........that I am aware of.....is checking the brakes.

SilverGhost · Mar 27, 2017

Wait a second, Passat wagon or Jetta wagon? Neither car of this vintage were, shall we say, forth coming with DTCs when something was amiss. Also Passats were relatively thirsty in comparison to Jettas. Both could get good mileage, but Passats always lagged behind in MPG contests.

Also specific to the Passat would be checking the torque convertor. They are more prone to failure than other models.

Quick check would be to jack car up until rear tire clears the ground and spin the tire. Shouldn't hear metallic rubbing nor should the tire stop quickly. Either or both happen you need to dig into the brakes.

Jason

ron hughes · Mar 27, 2017

it is a Passat. The car is shifting normally but who knows. I have a rack here so I can check it out. Thanks

Owain@malonetuning · Mar 28, 2017

Doubtful you'll break into the 40s without converting it to a manual, those automatics drink fuel. They're rated at 23 city 34 highway. Have a customer recently who claims he went from 36 to 49 with a manual swap. Odds are it's running just fine, low rolling resistance tires at 35 PSI and putting each corner in the air to check for trailing brakes is about all that's left to it. If it's been a dealer maintained car, they should have noticed anything peculiar.

SilverGhost · Mar 29, 2017

That's what I was thinking, but I didn't want to be the first

to say it. But that said the few I have seen the MFI fuel mileage usually is high 30's (most about 38mpg).

Jason

Owain@malonetuning · Mar 29, 2017

MFIs are liars though

filled at the pump vs distance on the clock or it doesn't count. I personally get 38-40mpg city/mixed ( I say mixed as traffic isn't too bad but I'm never cruising more than a couple miles or doing highway speeds) in my manual jetta wagon, stock with EGR delete, which if anything hurts mileage (need to change clutch). My friends automatic golf gets around 32 with a stage 1 (which helped with his failing transmission) in similar conditions. Automatics of this era unfortunately take a heavy mileage hit, it's a shame they didn't offer this as a manual because they're absolute beasts with mild remapping.

2004 TDI wagon horrible fuel mileage

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