Poor fuel mileage again

vwman2

Veteran Member
Joined
Feb 8, 2012
Location
Orange County NY
TDI
03 Jetta Wagon Tdi, 2010 Golf TDI
Well I have checked everything that could be cousing poor mileage and can't seem to figure it out. Dpf is far from being full, brakes are not dragging, tire pressure is normal, no codes, alignment is spot on,fuel filter is new,been diesel purged, use additives, air filter is new. Golf has 168k on it and was hoping to be getting better mileage as it aged rather then worse. I'm struggling to get 39mpg highway. Mileage did briefly go back to normal when I found the breather hose that comes off the air box was not connected, has not come off this time.

Please help!
Thanks
Jamie
 

TDIAustin

Veteran Member
Joined
Mar 19, 2013
Location
Austin, TX
TDI
2011 JSW, MT, Red/Cornsilk
How about just a cold weather effect? That has to cost you a few mpg I'm sure. Maybe you have no problem.
 

ATR

Top Post Dawg
Joined
Jun 18, 2005
Location
Baltimore
TDI
2011 Golf TDI 6MT
Did you check to see if you have any codes that may indicate a problem?
 

Henrick

Top Post Dawg
Joined
Aug 24, 2010
Location
Ireland
TDI
Golf VI TDI, 77 kW (CAYC)
Not familiar with N.A. TDI engines but have you checked EGR plumbing for excessive clogging?
 

psrumors

Veteran Member
Joined
Feb 14, 2013
Location
Cartersville, GA
TDI
MK4, MK6
How did you check brake drag?

I would go for a drive, one that will get the brakes used quite a bit so they are hot. Then use an infrared temp gauge to see if one rotor is hotter than the others
 

BamaB4S

Veteran Member
Joined
Oct 28, 2011
Location
AL
TDI
1996 Passat & 2006 Jetta
How many miles does she have on the wheel bearings?
 

vwman2

Veteran Member
Joined
Feb 8, 2012
Location
Orange County NY
TDI
03 Jetta Wagon Tdi, 2010 Golf TDI
I just jacked up each wheel and spun the wheels. Checked e-brake function to. All normal as I could tell
 

GAZNRN

Veteran Member
Joined
Sep 27, 2012
Location
Atlanta, GA
TDI
2012 JSW
I lose 2-3 MPG consistently driving the same trips same speeds when it gets & stays below 50 degrees. I make a trip to New England every winter and seen my mileage drop to 35-37 highway while I am up there. Must be the fuel map adjusting to temperatures.
 

vwman2

Veteran Member
Joined
Feb 8, 2012
Location
Orange County NY
TDI
03 Jetta Wagon Tdi, 2010 Golf TDI
front wheel bearings are new, rears were good, Im leaning towards the actuator now as I got on it today and it did not move like it normally does.
 

Tec80

Veteran Member
Joined
Feb 5, 2010
Location
IL
TDI
None
Check all inlet hose connections from air cleaner to turbo inlet.
 

TDIAustin

Veteran Member
Joined
Mar 19, 2013
Location
Austin, TX
TDI
2011 JSW, MT, Red/Cornsilk
I lose 2-3 MPG consistently driving the same trips same speeds when it gets & stays below 50 degrees. I make a trip to New England every winter and seen my mileage drop to 35-37 highway while I am up there. Must be the fuel map adjusting to temperatures.
When temps drop here from the 90's to the 50's with rain, as they just did, I saw my highway mileage drop by 5 mpg-this just happened yesterday as we are driving from Austin to Phoenix on I-10. I was only getting 33 mpg in the rain and cold temps. Later, when things dried up and warmed up a few degrees, I was getting low 40's.

The next day, today, from Las Cruces, NM all the way to Phoenix, it was dry and a bit warmer: We got nearly 46 mpg. Some of that is elevation decline into the desert where Phoenix is but, had it been even warmer (it was in the 50s and 60s), I think the mileage would have been even better.

In full disclosure, the first day we drove 80 mph and the second day 75, both of which were the speed limits of west Texas and then of New Mexico and Arizona. This I'm sure had a mild effect also.
 
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TDI_Coast2Coast

Veteran Member
Joined
Sep 6, 2009
Location
Lehighton, PA
TDI
2010 Jetta TDI SW 6spd Manual
Your intake manifold could be malfunctioning. My flaps were not operating correctly(opening fully), even when tuned out. I'm pretty sure mine was no good before 80k(before tune). I'm at 150k now. Unplugged it about 15k and a trip to Colorado ago.

I got about 5mpg gain on the highway after unplugging it. I can get 50mpg pretty easy now, where I could hit 45mpg max before. I can get 45mpg with an 18 cu Skybox on top now with a tail wind.

I had no CEL and no other symptoms other than a random hard start/white smoke and problems with my methanol injection. I also had low mpg's, but I figured it was the tires/driving style/etc. But mileage jump has continued...Car also runs/sounds better.

I know of at least one person who checked ash load after unplugging it and found no noticeable increase. I see little harm unplugging it just for testing purposes. Just don't idle it for long periods and don't lug it. They are supposed to be fully open by 3k if I remember correctly. Without a tune you will get a CEL.

http://www.natef.org/natef/media/natefmedia/vw files/2-0-tdi-ssp.pdf

Page 12 - Intake Flap Motor v157

If you unplug it, flaps should default open.

Mine was actually making a lot of noise on shut down, as if it could not figure out where to stop. If you open hood, then shut off car and go to manifold and listen, you can hear it positioning itself. I am not sure how long it takes normally, but mine was definitely taking much longer than normal to get to it's desired position. That is what led me to unplug it, which it remains until Les gets new intake manifold sections minus the flaps :)
 

vwman2

Veteran Member
Joined
Feb 8, 2012
Location
Orange County NY
TDI
03 Jetta Wagon Tdi, 2010 Golf TDI
I can check it but have not heard anything odd going on when shut off. Are there any vcds tests for this?
 

TDI_Coast2Coast

Veteran Member
Joined
Sep 6, 2009
Location
Lehighton, PA
TDI
2010 Jetta TDI SW 6spd Manual
I'm not sure about the vcds. The noise I got was only recently, though I'm pretty sure it was malfunctioning well before I noticed the odd noises. I could tell instantly once I unplugged it by the way it drove/sounded that the flaps were not fully opening. Again, on a stock car, it probably won't be as noticeable.

The only other thing I noticed in retrospect, was the lack of turbo lag I had before unplugging. Once unplugged, there was a hint of lag(visible via gauge), but the same PSI seemed to offer more actual boost.

It's one of those things that I think you can drive around with while it's not functioning, but not really notice it unless you get a CEL. For the most part, car drives normal.

Not saying it is what is behind your lower MPG's, but IMO a possibility that is relatively easy to test.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
Well I have checked everything that could be cousing poor mileage and can't seem to figure it out. Dpf is far from being full, brakes are not dragging, tire pressure is normal, no codes, alignment is spot on,fuel filter is new,been diesel purged, use additives, air filter is new. Golf has 168k on it and was hoping to be getting better mileage as it aged rather then worse. I'm struggling to get 39mpg highway. Mileage did briefly go back to normal when I found the breather hose that comes off the air box was not connected, has not come off this time.
Please help!
Thanks
Jamie
You say that you're struggling to get 39 MPG highway, but your Fuelly account shows that you haven't had any fillups below 43 MPG. Can you clarify? :confused:
 

vwman2

Veteran Member
Joined
Feb 8, 2012
Location
Orange County NY
TDI
03 Jetta Wagon Tdi, 2010 Golf TDI
I got my vcds today and when I checky readyness egr won't go ready and I can't see dpf loading. Am I on to something hear?
 

TDI_Coast2Coast

Veteran Member
Joined
Sep 6, 2009
Location
Lehighton, PA
TDI
2010 Jetta TDI SW 6spd Manual
Regarding the HP EGR, I deleted mine a few thousand miles after unplugging the intake manifold. I did notice that my mileage on short trips took a hit, which I attribute to slower warm up. So I guess if your HP EGR is malfunctioning, that could effect your warm up time, hence lowering your MPG's, but on longer trips(when car is warmed up), I would they they would be close to normal. Perhaps I am wrong in that assumption.

My personal belief is that that the intake manifold malfunction + HP EGR malfunction are somewhat related...Meaning one failure can cause failure of the other and vice versa and/or lead to other issues down the road.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
Your looking at the wrong car
Ack! Right you are... I was looking at your wagon, not the Golf. The Golf definitely is lower than it has been in the past... I assume that your driving style and commute haven't changed?
 

vwman2

Veteran Member
Joined
Feb 8, 2012
Location
Orange County NY
TDI
03 Jetta Wagon Tdi, 2010 Golf TDI
Same drive to work,

I can't see dpf statistics in group 075 but I found a way to see that it last regenerate for around 10 miles ago. Says its 3.9 grams soot load. Nothing is making any sence. Not getting readyness on egr
***
 

TDI_Coast2Coast

Veteran Member
Joined
Sep 6, 2009
Location
Lehighton, PA
TDI
2010 Jetta TDI SW 6spd Manual
Do you know if it's the LP or HP that is not ready?

http://www.natef.org/natef/media/natefmedia/vw files/2-0-tdi-ssp.pdf

If you look at page 57, it states the LP helps engine and DPF to reach it's operating temp quicker. I know warm up times affect my mileage greatly, so I would assume if it was not operating as designed, the engine/dpf would warm up slower, which I would say would lower your mileage, mostly when it was colder at start up/short trips.

Since you say your EGR is reading not ready, I would say that is at least a place to start. Sorry I can't help you reference, as I don't have those parts to check readiness of...

The above has lots of good diagrams for those not as familiar with the function of different systems. It's far from complete and may differ slightly, but you can get a good feel of how everything works together functionally and is connected physically.

Probably a similar one on the site, but I happen to have that link saved.
 

vwman2

Veteran Member
Joined
Feb 8, 2012
Location
Orange County NY
TDI
03 Jetta Wagon Tdi, 2010 Golf TDI
The exact messages I see are
Catalyst monitoring failed or incomplete
Heated catalyst monitoring failed or incomplete
Secondary air system monitoring failed or incomplete
Oxygen sensor monitoring failed or incomplete
Oxygen sensor heater monitoring failed or incomplete
Exhaust gas recirculaton failed or incomplete

I have no codes though... Don't get it
 

TDI_Coast2Coast

Veteran Member
Joined
Sep 6, 2009
Location
Lehighton, PA
TDI
2010 Jetta TDI SW 6spd Manual
That seems to point to LP EGR function, but I could be wrong.

On page 57 of the PDF, it says if the EGR valve N345 or the EGR potentiometer fails, the LP EGR will be deactivated. It does not state that a CEL will be triggered, as it does for other failures.

And as I pointed out above, it states that proper function helps bring engine/DPF up to operating temp quicker. So it only makes sense to me that improper function would extend warm up time, therefore affecting mileage.
 
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