2003 Jetta Automatic Poor Mileage

ndamico

Vendor , w/Business number
Joined
Mar 20, 2008
Location
Sacramento, CA
TDI
2003 Golf 2Dr TDI, 2003 Jetta TDI, 2003 Jetta Wagon TDI, 2002 Duramax, 2003 Duramax
First off I know automatics get worse mileage. Here is the scenario. My friend and I both have 2003 Jetta TDI's. mine is a manual w/ 114k on it and his is an auto with 78k on it. both have same size tires. Mine is a GLS, his is a GL. Mine get great mileage (Upper 40's) and his is stuck in the mid to high 20's...

Observations/what we've done:

Mine is substantially faster (i know mine is a manual and his isn't)
We have removed the snow screens from both cars (they were both plugged)
we have reaplced the air filters and fuel filters with OEM replacements.
Both cars idle smooth, start the same, run quietly and otherwise appear just fine.
I have made a few datalogs with Vag-Com which i will attach. I just got the software a week ago and haven't had much time to use it.


However as i said his mileage somewhat sucks and mine is great and we are having a very hard time believe its just because his is an auto.

any help would be greatly apprecaited!

Here is my acutal vs desired timing.. scale on timing is 10*:



Here is the same thing from the auto with poor mileage...scale on timing is set to 20*:



it appears his may be off more at low RPM, but does it matter?


Here is the automatic's MAF data. it does appear under WOT the the maf reading for actual will start to fall. is this ok?




Here is a screenshot of his measuing blocks i took:






Lastly, after he left my house i realized how to get the timing plug-in to VAG-COM to work :(. Here is what it shows on my vehicle. It says "Timing within spec, slightly advanced". is that good?





Thank you again. I've found this site invaluable. I come from the Duramax diesel family so i'm new to TDI's but not to diesels.
 
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scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
Can you define (in numbers) what you mean by "his MPG sucks" ?

From long experiance, if the automatic is getting 37-40 MPG in mixed use, he's doing pretty good.
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
1) try running w/o the maf...see if things improve (just unplug the wire harness) if so then try cleaning the wire harness and maf connector with deoxit and wiggling it around a bit...see if that fixes it. if not...and running without helped, then replace the maf.

2) check to make sure no vac lines are unplugged

3) if no vac lines are unplugged then replace all vac lines (about an hour and $10)

4) if none of the above then check the turbo actuator (there are threads on how).

5) if none of the others then try the other things in the 101 section on troubleshooting.
 

ndamico

Vendor , w/Business number
Joined
Mar 20, 2008
Location
Sacramento, CA
TDI
2003 Golf 2Dr TDI, 2003 Jetta TDI, 2003 Jetta Wagon TDI, 2002 Duramax, 2003 Duramax
We tried unplugging the MAF already (forgot to mention that) and the car runs worse for sure. from what i can tell that means the MAF isn't bad, correct?

i'll have him check vacuum lines.

we've monitored the map sensor and it definately makes boost when it should. the car isn't slow and seems to run great, minus the poor mileage.

intake plugged is possible, but i thought that would manifest itself in the MAF not being able to get to 800 on a WOT run?

i am getting a clean intake manifold for my car and once i swap it we're going to clean mine and move it over to his car.

any comments on the data i posted about timing, etc?
 

tttthumper

Veteran Member
Joined
Jan 9, 2008
Location
Pickering, Ontario
TDI
2006 Jetta TDI
Do you have a Scangauge?
That would make things alot easier.

Do you drive his car and get same bad mileage as him?
What if he drives your car (if he drives standard)?

Same size tires and the pressure is the same as yours?
 

ndamico

Vendor , w/Business number
Joined
Mar 20, 2008
Location
Sacramento, CA
TDI
2003 Golf 2Dr TDI, 2003 Jetta TDI, 2003 Jetta Wagon TDI, 2002 Duramax, 2003 Duramax
we both have scanguages..

we haven't switched drivers, but we have followed eachother on some trips to compare data while driving. we are going the same speeds and basically accellerating in a similar fashion.

we both have the same size tires. air pressure is within a few pounds between cars.

our scanguages seem to accurately reflect the mileage differences we are seeing.

he is trying to post in this thread but i think he didn't activate his account. he's emailed the admin so hopefully he'll get that resolved and will be able to comment as well.

tttthumper said:
Do you have a Scangauge?
That would make things alot easier.

Do you drive his car and get same bad mileage as him?
What if he drives your car (if he drives standard)?

Same size tires and the pressure is the same as yours?
 

ndamico

Vendor , w/Business number
Joined
Mar 20, 2008
Location
Sacramento, CA
TDI
2003 Golf 2Dr TDI, 2003 Jetta TDI, 2003 Jetta Wagon TDI, 2002 Duramax, 2003 Duramax
regarding his scangauge, we swapped MAF's today and no change. if he disconnects his MAF his car has much less power, but crusing down the freeway at 65MPH nets him about 20 MORE MPG according to the scanguage.

what does that mean? also the load value on the scangauge is lower.
 

riverman

Member
Joined
Jul 8, 2008
Location
roseville ca
TDI
2003 auto trans jetta
Nick , thanks for helping me with my poor fuel economy problem,, so .....
I purchased a 2003 jetta 77k miles auto trans 1 owner last month
runs good , seems to have ok power,, pulls through entire rpm range
checked fuel consumption on long highway trip using pad and pen, 28mgp!
replaced fuel and air filter ,checked vaccume lines , unplugged (ran poor with unplugged) mas air sensor ., borrowed nicks mas and no change to mgp using scan guage 28 mpg at 60 mph with no a/c
now here's where it gets interesting !!!! I forgot to plug the mas sensor in today when leaving nicks house and guess what -- 45 mpg at 60 mph using scan guage! I did get p0102 (mas air error ) while drive the 20 miles home but 45 mpg !!!! so... i plugged in the sensor and did a test drive on the freeway at 60 mph , now back to 28/29 mpg for a 20 mile run,, so... unplugged the mas and back to 45 mpg !!
Here is a bit more info , lod at idle in park w/no a/c i get 24 lod
unplug the mas and i get at idle in park w/no a/c lod of 18
Everything seems better (lod /mpg ) with mas unplugged ,except much less power.
I dont know if this info helps, but thanks in advance as i am a new tdi owner
Thanks also to my new friend Nick who is also an new tdi owner who just happens to live in Sacramento and is one hell of a guy!
Sorry for the long reply ,but the belt and tensioner were also replaced (2 months ago ) at the dealer before i purchased the car
 

bayshorecs

Veteran Member
Joined
Mar 18, 2006
Location
SoCal (Rancho Cucamonga)
TDI
06 Golf
Talking out of my a$$ here, but just expanding on a thought...

- you swapped the MAF with a known working MAF. Same results, low MPG. This rules out the MAF itself.
- you unplug the MAF so the ECU no longer reads the measured values and defaults to control values, MPG increases. This means there is something air related.
- You cleaned the snowscreen and air filter
- You have not checked/cleaned the intake

Sounds like you have an air restriction to me. I would clean the intake and maybe the intercooler to be sure you are getting good air flow to the motor. There may be enough air flow to breath well enough with the MAF unplugged, but with it plugged in, the car is reading the true values and trying to compensate.

Could be COMPLETELY wrong, but the intake cleaning is what I would try next.
 

bluesmoker

Veteran Member
Joined
Jun 7, 2006
Location
Maple Ridge, B.C.
TDI
2004 pd 5 speed tip
bayshorecs said:
Talking out of my a$$ here, but just expanding on a thought...

- you swapped the MAF with a known working MAF. Same results, low MPG. This rules out the MAF itself.
- you unplug the MAF so the ECU no longer reads the measured values and defaults to control values, MPG increases. This means there is something air related.
- You cleaned the snowscreen and air filter
- You have not checked/cleaned the intake

Sounds like you have an air restriction to me. I would clean the intake and maybe the intercooler to be sure you are getting good air flow to the motor. There may be enough air flow to breath well enough with the MAF unplugged, but with it plugged in, the car is reading the true values and trying to compensate.

Could be COMPLETELY wrong, but the intake cleaning is what I would try next.

agreed, also check the intake where the egr connects, could be fully of carbon
 

riverman

Member
Joined
Jul 8, 2008
Location
roseville ca
TDI
2003 auto trans jetta
thanks for the thought ,, i feel as if i am talking out of my a$$ when it comes to a diesel... i can repair most problems with my wifes subaru but the jetta is a different story
I told Nick last night ," I have never worked so hard to repair a car that runs so great " usually when the subaru is having problems it acts up ,kicks,sputters and a diagnosis is very simple
My jetta runs great,shifts great and has a fair amount of power, but 28 mpg on the highway is what the gasser will do !
Next week i will clean the intake and get back to you guys with the results.
Mabey unplugging the MAF is a good way to check if your manifold it blocked !
Thanks to everyone
 

tttthumper

Veteran Member
Joined
Jan 9, 2008
Location
Pickering, Ontario
TDI
2006 Jetta TDI
Just my $0.02 worth.
Would the intake get that clogged up after only 74k?

Great troubleshooting, it's always great to know that your narrowing down the problem, and say...... Nope it's not that or that, that's working etc.
 

bayshorecs

Veteran Member
Joined
Mar 18, 2006
Location
SoCal (Rancho Cucamonga)
TDI
06 Golf
Depends on the driver.

Once a problem of clogging starts, you get more and more restriction causing the air flow lower and lower which will increase the clogging rate.

Basic rule of thumb on diesels before any other troubleshooting. You need:

Air
Fuel
Compression

Without knowing those 3 are good, you are "pi$$ing in the wind".
 

riverman

Member
Joined
Jul 8, 2008
Location
roseville ca
TDI
2003 auto trans jetta
Thanks for the reply guys,, the lady i purchased the car from was the oringinal owner,, in 40 's ,very conservative, for sure not a Mario Andertti.
Here is some more info,, it is a automatic and lod numbers at idle (scan guage) are twice a much as Nicks 5 speed car. If anyone with a automatic has a chance to check lod at idle with A/C off in park with a warmed up car i would be interested .
mine are :
lod in park no a/c 22
in gear with parking brake on lod 29
in gear with parking brake on , with a/c/ running 39
60 mph level road , cruise on, with no a/c running lod is 80 %,, 29 mpg.
I know it is not MAF, fuel filter,air filter,and no errors reported using a vag-com,, It does not smoke or give any indications of have a problem, timming checked with vag-com is in spec.
It sure sounds like intake, but i am trying to eliminate all other possibilities before jumping into the intake removal
Thanks again
 
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EARL97850

Veteran Member
Joined
Jul 17, 2001
Location
Eastern Washington
TDI
N/A
No Vag-Com data...in fact no data at all to back up my claim. My auto gets about a 40mpg average over it's 62K life.

I have not checked my intake for clogging or had any problems with the MAF going bad. I guess I've just been lucky so far.

Cya
 

N2OKX

Well-known member
Joined
May 22, 2005
Location
Kentucky, Western
TDI
looking
I have been working on two '02 TDIs with automatic transmissions. Both have right at 100K miles. The Jetta is getting 35 mpg and the New Beetle is 33 mpg, conservative highway driving. I have replaced the MAF sensors, removed the snow screens, checked the injection timing, checked for carbon in the EGR valve, checked the N75 valve, and clocked the performance with a Vag-com. Everything checks out fine. The MAF value is good and the boost pressure is good. Both cars run great (for automatics).

I decided to search this site one more time for some ideas of where to go from here and discovered this thread. Someone else has the same problem! ...but no solution. Okay, you geeks and gurus, any ideas?

Also, what is "lod" in Riverman's post? I'd be happy to read mine and report the results. It looks like it may be an indicator of the mpg. Is there a vag-com read out of this? I realize you can take the reading of miles or mph and divide by fuel injection quantity or some such values, but I have not tried this. I've been adding two gallons of fuel at a time and seeing how far I get before it beeps for low fuel. It has been a very consistent method, much to my surprise. I guess as I continue to diagnose for a cure, it would help to see instant results.

I'm about ready to take these cars back to auction, but I have yet to have a VW problem that I can't solve, often with help from this site. :)
 

turbobooster

Veteran Member
Joined
Apr 22, 2006
Location
IN
TDI
2000 Golf GLS 5-speed (sold); 2011 Golf TDI 6-speed manual
Don't be fooled by the mileage reported by the Scangauge when you unplug the MAF. If the MAF is unplugged, you have to recalibrate the Scangauge to get the correct, actual mileage. I've experimented with it quite a bit, and the increase reported with the MAF unplugged isn't real.

Good luck.
 

riverman

Member
Joined
Jul 8, 2008
Location
roseville ca
TDI
2003 auto trans jetta
this is really bad

this weekend i removed all injectors and cleaned them,inside and out, they now atomize the fuel and no holes piss.
I then used the fuel lines to make the injectors fire into the air while turning the motor over . The injectors work great.
I put the car the injectors back into the motor, bled the air out , started the car and drove for 1/2 hour,, i still get 28 mpg at 60 mph using scan guage, i also have very low power, my boost is up to 15 lbs but i would be supprised if the car has 60 hp. I cracked the fuel lines at the injectors while idle and rpms drop at each cylinder,just like removing a spark plug wire on a gas car. The car does not smoke ever, you would not even no it is a diesel.
I have tried everything, checked vaccum lines,air filter,fuel filter,half ass rebuilt the injectors,swapped MAF,
The car is SLOW , i know the turbo is working, the boost hose that connects to the egr swells when reving the motor,, i also looked through the egr into the intake manifold and it does not seem clogged.
My scan guage shows a lod or 20 at idle in park with no ac on.
If i put it in drive lod goes up to 33
if i drive the car lod goes up to 80 to 90 with very little throttle
I know i am missing something but i cannot figure it out
I am ready to sell the car, but i really want to fix it, it is the perfect auto for us if it had power and got high 30s to low 40s at 60 mph
any ideas
my last hope is another check of the timing
Thanks for everyones help
 

ndamico

Vendor , w/Business number
Joined
Mar 20, 2008
Location
Sacramento, CA
TDI
2003 Golf 2Dr TDI, 2003 Jetta TDI, 2003 Jetta Wagon TDI, 2002 Duramax, 2003 Duramax
Are you saying its worse now that you've pulled the injectors and put them back in? The car never seemed poor on power before?

how did you fix the injector holes that were pouring fuel instead of atomizing?
 

riverman

Member
Joined
Jul 8, 2008
Location
roseville ca
TDI
2003 auto trans jetta
power is way down,, like no turbo,but MAP shows 15 lbs boost at high rpm,
I used a dremel tool with a soft brass wire brush attached. The injectors pattern seem very good,
Power is way down, it would not go up a mountain road
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
I don't think I would have hit the injector nozzles with the dremel, I suspect it's possible you damaged them.

I think you hit upon the problem earlier on when you said you unplugged the maf and the problem went away...you should have kept looking there rather than just moving on. I don't usually watch this forum otherwise I would have spoke up sooner. This sounds to me like your wire harness is having problems. I would try cleaning out the harness and maf with some deoxit. Unplug and plug it in a few times. The connectors can get oxidized and start causing problems like this.

If that doesn't work, then I hate to say it but it may be worthwhile trying to swap wire harnesses. All it takes is one flakey pin to give the ecu bad data, that would also explain why swapping mafs did not help.

Before you deal with the maf though, you need to make sure you didn't damage anything with that dremel. I would suggest unplugging the maf entirely and see if your power comes back. If it doesn't then you have a whole different road of troubleshooting to go down before you get back to the maf.

I suggest you move this post to the General TDI Maintenance section? This is really I would say more of a maintenance item than a fuel economy optimization issue.
 

ndamico

Vendor , w/Business number
Joined
Mar 20, 2008
Location
Sacramento, CA
TDI
2003 Golf 2Dr TDI, 2003 Jetta TDI, 2003 Jetta Wagon TDI, 2002 Duramax, 2003 Duramax
Update - Randy changed out his injectors for a set of used one. He's now getting 40+ MPG!! Hopefully he'll come back and comment but i wanted to put an update out in case anyone else is in the same boat.
 
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