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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old August 18th, 2009, 05:06   #1
SootFoot
Veteran Member
 
Join Date: Aug 2005
Location: Midwest USA
TDI(s): Sold
Exclamation Only getting avg of 35mpg for 50/50 city/highway mix

Low mpg another issue besides the crrent glow plug mismatch on our 2005 TDI (mismatch from a March 2009 warranty repair). Since its my wife's car I haven't stayed on top of it as well as I should, but I think I can correlate the mpg drop beginning to exhibit after a bad glow plug on the #2 cyl was replaced then exactly two weeks later the CEL came back on and it was the MAF and Oxygen Sensor. I don't know if that pattern indicates anything, but it was roughly after these repairs that the MPG started going south. This was quite awhile ago, actually, in late 2008.

The Tandem Pump was also replaced shortly after the Oxygen Sensor and MAF, due to an oil leak, but a new tandem pump would not be responsible for increased fuel consumption... would it?

For reference, the car was able to achieve 50mpg on the interstate and around 42 mpg in town prior to this.

It could certainly be something else, but I am just trying to correlate the loss of efficiency to known events with the engine.

Oil consumption has increased significantly as well along the same time line. Used to consume maybe 1/4 liter for a 10,000 mile OCI. Now more like 3/4 of a liter for the OCI.

42,000 miles on the car.

It does get short journey cycles, real short, because my wife's place of employment is only about 5 miles from home. In hindsight a diesel probably not the optimal choice for such short trip commuting during the week, but she does get it out and run it longer on lunch breaks, etc through the week and then on weekends it is driven longer periods.
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Old August 18th, 2009, 08:19   #2
BobnOH
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Join Date: May 2004
Location: central Ohio
Fuel Economy: 50/45/35
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Quote:
Originally Posted by SootFoot
...... then exactly two weeks later the CEL came back on and it was the MAF and Oxygen Sensor.........................It could certainly be something else, but I am just trying to correlate the loss of efficiency to known events with the engine.

Oil consumption has increased significantly as well ..........
Definetly smart to consider recent engine events when troubleshooting.
I have no idea what OCI stands for.??
Glow plugs shouldn't affect mileage. Did you replace MAF, Oxygen Sensor?
The oil increase sort of points to turbo, but don't replace unless you're sure.
It should be good for the car to be driven wide open maybe once a week or so. Just be sure the engine is warm and you have safe conditions to floor it in gears 1-4.
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Old August 18th, 2009, 08:20   #3
SootFoot
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Join Date: Aug 2005
Location: Midwest USA
TDI(s): Sold
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I should mention that the except for what feels like a little bit more lag below 2000rpm than it had before, the car pulls strong when you give it pedal (firm throttle above 2000 rpm), as strong as when it was new.

OCI = Oil Change Interval. I adhere to the 10,000 mile OCI. The MAF and Oxy sensor were done under warrany by dealer.
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Last edited by SootFoot; August 18th, 2009 at 08:23.
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