www.tdiclub.com

Economy - Longevity - Performance
The #1 Source of TDI Information on the Web!
Forums Articles Links Meets
Orders TDI Club Cards TDIFest 2016 Gone, but not forgotten VAG-Com List Unit Conversions TDIClub Chat Thank You

Order your TDIClub merchandise and help support TDIClub


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.

Reply
 
Thread Tools
Old December 15th, 2018, 21:39   #1
montanajetta
Newbie
 
Join Date: Dec 2018
Location: Southwest Montana
Default Mass Air or Turbo issue?

New to TDI's and the forum. I have been searching the forums for an answer, with no luck. I have a 2002 Jetta Wagon have had a reduction in mpg and no power above 3400 rpm. I logged my Mass Air on my VCDS (as stated on ross tech) and noticed the graph was surging. I assumed I needed to replace my mass air sensor, until I noticed my boost followed the same wave. Does this still lead to a bad mass air sensor or another problem? Thanks for the help!
https://www.dropbox.com/s/gu9u4g2spp...graph.jpg?dl=0
https://www.dropbox.com/s/snafusgd50...graph.jpg?dl=0
montanajetta is offline   Reply With Quote
Old December 15th, 2018, 22:01   #2
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default

Seems VERY similar to my situation before I got it mostly fixed. My car had the exact same "MAF waves". Step on the pedal, MAF briefly gives a proper value, then falls, then comes back up a bit, falls, comes back up, falls. Each time the bounce gets lower and lower.

My car ran so poorly with the MAF plugged in, I drove with it unplugged just to be able to achieve high way speeds. The car was just plain gutless, and would slow to a stop up hills.

I would recommend a few easy, free tests:
First, unplug the MAF and see what changes.
Then unplug the vacuum line that goes down to the turbo vane actuator.

When I unplugged the vacuum line, it was like this weird...'calming of the storm'. Where my car had low power, but it...worked. I step on the pedal, it went faster. All my MAF graphs immediately whipped into shape, and it worked perfectly, just without the boost.

I eventually narrowed my issue down to my turbo vane actuator rod being out of adjustment and over boosting immediately, so my car would actually trip into limp mode at the very first throttle demand. It would literally go into limp mode on flat ground within .5 seconds of being started up.
When the computer trips limp mode, it cuts fuel heavily (among other things). So you've got low power on top of low power conditions.

When I disconnected the vacuum line (effectively removing the turbo from the equation), the turbo could no longer overboost and trip limp mode, so the computer spit proper fuel into the car based on proper MAF values.

But it could be other things too
2000alhVW is offline   Reply With Quote
Old December 15th, 2018, 22:14   #3
montanajetta
Newbie
 
Join Date: Dec 2018
Location: Southwest Montana
Default

Quote:
Originally Posted by 2000alhVW View Post
Seems VERY similar to my situation before I got it mostly fixed. My car had the exact same "MAF waves". Step on the pedal, MAF briefly gives a proper value, then falls, then comes back up a bit, falls, comes back up, falls. Each time the bounce gets lower and lower.

My car ran so poorly with the MAF plugged in, I drove with it unplugged just to be able to achieve high way speeds. The car was just plain gutless, and would slow to a stop up hills.

I would recommend a few easy, free tests:
First, unplug the MAF and see what changes.
Then unplug the vacuum line that goes down to the turbo vane actuator.

When I unplugged the vacuum line, it was like this weird...'calming of the storm'. Where my car had low power, but it...worked. I step on the pedal,
it went faster. All my MAF graphs immediately whipped into shape, and it worked perfectly, just without the boost.

I eventually narrowed my issue down to my turbo vane actuator rod being out of adjustment and over boosting immediately, so my car would actually trip into limp mode at the very first throttle demand. It would literally go into limp mode on flat ground within .5 seconds of being started up.
When the computer trips limp mode, it cuts fuel heavily (among other things).
So you've got low power on top of low power conditions.

When I disconnected the vacuum line (effectively removing the turbo from the equation), the turbo could no longer overboost and trip limp mode, so the computer spit proper fuel into the car based on proper MAF values.

But it could be other things too

Interesting, I will try unplugging the mass air sensor tomorrow. Will the car go into limp mode without throwing a code? I donít seem to have any codes, and can still get up to speed and hold speed up hills, but after 33-3400 rpm itís like the can loses almost all power....
montanajetta is offline   Reply With Quote
Old December 15th, 2018, 22:27   #4
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default

Quote:
Originally Posted by montanajetta View Post
Interesting, I will try unplugging the mass air sensor tomorrow. Will the car go into limp mode without throwing a code? I don’t seem to have any codes, and can still get up to speed and hold speed up hills, but after 33-3400 rpm it’s like the can loses almost all power....

"Can car go into limp mode without throwing a code?"

Short answer: Yes. My car NEVER threw a CEL (dash light illuminated) for ANYTHING, despite having pending and current codes logged. Additionally, I could drive my car for hundreds of miles in "limp mode" before ANY codes would show up when checking via VCDS. This sent me into somewhat of a fury that these ECMs are quite stupid.

Long answer:
I'm not really sure the answer of this. For a couple of reasons...
I've found this particular question/topic/point to be seldom directly talked about. The relationship between limp mode and CEL has gotten mixed answers when I've read.
The ambiguous part, for me, is the "limp mode" itself. Like, what is it really? I've poked around quite a bit with VCDS and haven't found any sort of data box or anything to indicate whether limp mode has been tripped or not. Maybe this is the fact that my car is an early version (2000) and not as intelligent as later models, but I'm almost convinced that the computer itself might not even know it's operating in limp mode.
It might just dumbly be bumped over to an alternate fuel map, similar to, say, open loop fueling during cold starts on a gas car.

To me, it would be super obvious computer logic. IF overboost, then throw into limp mode immediately (which it does) and then trip an overboost code which lights up CEL.
But no such thing happened for me. In my case, the ECM was utterly useless, and VCDS scanning/datalogging was only mildly helpful. I only solved my issues by getting down into nitty gritty old-fashioned mechanical diagnosis/logic.
2000alhVW is offline   Reply With Quote
Old December 15th, 2018, 22:50   #5
indysoto
Veteran Member
 
indysoto's Avatar
 
Join Date: Mar 2004
Location: Eugene, OR
Default

Clogged fuel filter? Or gunked up manifold?
__________________
2000 a4,G60 single mass, KYB AGX(replaced 2x :|), 215/65/r16's...
2004 BEW Wagon w/ Meyerhoff AutoHaus Runonbeer Sticker
indysoto is offline   Reply With Quote
Old December 16th, 2018, 05:53   #6
montanajetta
Newbie
 
Join Date: Dec 2018
Location: Southwest Montana
Default

Quote:
Originally Posted by 2000alhVW View Post
"Can car go into limp mode without throwing a code?"

Short answer: Yes. My car NEVER threw a CEL (dash light illuminated) for ANYTHING, despite having pending and current codes logged. Additionally, I could drive my car for hundreds of miles in "limp mode" before ANY codes would show up when checking via VCDS. This sent me into somewhat of a fury that these ECMs are quite stupid.

Long answer:
I'm not really sure the answer of this. For a couple of reasons...
I've found this particular question/topic/point to be seldom directly talked about. The relationship between limp mode and CEL has gotten mixed answers when I've read.
The ambiguous part, for me, is the "limp mode" itself. Like, what is it really? I've poked around quite a bit with VCDS and haven't found any sort of data box or anything to indicate whether limp mode has been tripped or not. Maybe this is the fact that my car is an early version (2000) and not as intelligent as later models, but I'm almost convinced that the computer itself might not even know it's operating in limp mode.
It might just dumbly be bumped over to an alternate fuel map, similar to, say, open loop fueling during cold starts on a gas car.

To me, it would be super obvious computer logic. IF overboost, then throw into limp mode immediately (which it does) and then trip an overboost code which lights up CEL.
But no such thing happened for me. In my case, the ECM was utterly useless, and VCDS scanning/datalogging was only mildly helpful. I only solved my issues by getting down into nitty gritty old-fashioned mechanical diagnosis/logic.
Very interesting. I have been having this issue for a while. Good to see some possible answers.
montanajetta is offline   Reply With Quote
Old December 16th, 2018, 05:58   #7
montanajetta
Newbie
 
Join Date: Dec 2018
Location: Southwest Montana
Default

Quote:
Originally Posted by indysoto View Post
Clogged fuel filter? Or gunked up manifold?
I just replaced the fuel filter and ran a can of diesel purge. I also pulled the inter cooler and drained the oil at the same time.

I was leaning towards either the mass air sensor or a possible clogged intake manifold. I saw the tutorial on cleaning, is there a way to tell if it is clogged without pulling it all the way off?
montanajetta is offline   Reply With Quote
Old December 16th, 2018, 08:26   #8
eddieleephd
Veteran Member
 
Join Date: May 2012
Location: Asheville, NC
Fuel Economy: 38mix / 47@70-75
Default

Look down the egr and see inside.

http://forums.tdiclub.com/showthread.php?t=179589
__________________
'02 1.8t Jetta Wagon Alh w/5spd swap, SB 21#SM DD, bew lift pump, 11mm IP, VNT17, Malone stage4 tune, Stealth pipe, BMW Cyclonic CCV filter, 2.5"cat back st. pipe,Vr6 brakes, 2" lift, Panzer, Bilstein HD, fill tube ectomy, soon to be Bosio DLC 1020's PD_fuel_delivery TDI Search Plug release tool Howto terminal release tools VW/Audi
eddieleephd is offline   Reply With Quote
Old December 16th, 2018, 09:24   #9
montanajetta
Newbie
 
Join Date: Dec 2018
Location: Southwest Montana
Default

Quote:
Originally Posted by eddieleephd View Post
Look down the egr and see inside.

http://forums.tdiclub.com/showthread.php?t=179589
I will check the EGR when I get home. Thanks for the link!
montanajetta is offline   Reply With Quote
Old December 16th, 2018, 18:10   #10
montanajetta
Newbie
 
Join Date: Dec 2018
Location: Southwest Montana
Default

So I unplugged the Mass Air Sensor, No noticeable change. Not sure what that means. Any ideas? Pulled off the EGR and then the intake. It might be some of the problem.

https://www.dropbox.com/s/lfu771wcg1...%2008.jpg?dl=0

https://www.dropbox.com/s/bo9vudxbjs...%2039.jpg?dl=0

https://www.dropbox.com/s/924kel9gq3...%2047.jpg?dl=0
montanajetta is offline   Reply With Quote
Old December 16th, 2018, 21:00   #11
indysoto
Veteran Member
 
indysoto's Avatar
 
Join Date: Mar 2004
Location: Eugene, OR
Default

Looks clogged!
It is the SUM = Your Problem
Merry Christmas!
You got a lump of Diesel coal
__________________
2000 a4,G60 single mass, KYB AGX(replaced 2x :|), 215/65/r16's...
2004 BEW Wagon w/ Meyerhoff AutoHaus Runonbeer Sticker
indysoto is offline   Reply With Quote
Old December 16th, 2018, 22:16   #12
mrfiat
Veteran Member
 
Join Date: Mar 2008
Location: Los Ranchos, NM
Fuel Economy: 38.5 mpg (in town - trying to improve it)
Default

I paid the NAPA machine shop $30 to clean my intake out. It's a messy job. People also burn out the gunk with a torch. (read up on the method here before trying it)
mrfiat is offline   Reply With Quote
Old December 17th, 2018, 00:07   #13
Nero Morg
Veteran Member
 
Nero Morg's Avatar
 
Join Date: Oct 2017
Location: OR
Default

Quote:
Originally Posted by mrfiat View Post
I paid the NAPA machine shop $30 to clean my intake out. It's a messy job. People also burn out the gunk with a torch. (read up on the method here before trying it)
NAPA does that? So you mean the four days of soaking in Zep and scrubbing could have been avoided? I still have a flathead screwdriver covered in that sludge.
__________________
Whatever. Just use your darned blinker. And stay off your phone.
Nero Morg is online now   Reply With Quote
Old December 17th, 2018, 01:41   #14
ToxicDoc
Veteran Member
 
Join Date: Mar 2018
Location: US
TDI(s): 2001 Jetta
Default

Quote:
Originally Posted by Nero Morg View Post
NAPA does that? So you mean the four days of soaking in Zep and scrubbing could have been avoided? I still have a flathead screwdriver covered in that sludge.
Any general automotive machine shop can do it - some NAPA, Car Quest, locations have them. They just run parts like that through the hot tank (or whatever is currently in since many have gotten away from the chemicals and EPA requirements).

Last edited by ToxicDoc; December 17th, 2018 at 01:43.
ToxicDoc is offline   Reply With Quote
Old December 17th, 2018, 05:26   #15
montanajetta
Newbie
 
Join Date: Dec 2018
Location: Southwest Montana
Default

Awesome. Going to try and clean it today. I’m not sure anyone in town will touch it, so I have been reading up on the cleaning methods. What about the passages is the block? Should I clean those at this time?
montanajetta is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Difference between Air Mass Specified, and Air Mass Actual WEGSVDUB OBD Scanners 8 August 23rd, 2013 10:14
Mass Air Flow sensor issue kpenner TDI 101 13 December 1st, 2010 10:34
Mass air flow issue Rod 525 TDI 101 5 August 15th, 2008 19:38
air mass leoncupra OBD Scanners 4 May 9th, 2007 17:44
137,000 miles, 4000 miles ago had a new turbo, fuel filter, and mass air sensor... brian rhodes VW MKIV-A4 TDIs (VE and PD) 11 May 13th, 2002 12:16


All times are GMT -7. The time now is 12:07.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright - TDIClub Online LTD - 2017
Contact Us | Privacy Statement | Forum Rules | Disclaimer
TDIClub Online Ltd (TDIClub.com) is not affiliated with the VWoA or VWAG and is supported by contributions from viewers like you.
© 1996 - 2017, All Rights Reserved
Page generated in 0.16919 seconds with 13 queries
[Output: 131.66 Kb. compressed to 110.89 Kb. by saving 20.76 Kb. (15.77%)]