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




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 September 9th, 2018, 17:15   #1
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default Narrowing down low power causes

My car has suffered from low power for a long time.
The symptoms are.... no power. That's it. No noticeable black smoke or soot (it does smell a bit strong though), and no obvious issues. Someone like my mother could drive the car indefinitely with no complains other than "its VERY slow". Very hard to trip a DTC. When it does trip, it is P1556.
I have a VCDS. At very low throttle, the car does okay. And the measured vs actual MAF values stay kinda close. Anything more than 20% throttle, and they deviate wildly. When increasing throttle, the actual MAF reading will decrease. I read an article on KermaTDI that might answer why - when the computer senses an underboost issue occurring, it cuts back fuel. So basically, as I try to increase throttle, the computer cuts even more power.
Things I've done:
  • Replaced MAF. Bought new Bosch MAF off eBay. zero change. I also grabbed an unknown MAF (OEM Bosch) from the junkyard and put that in. Zero change.
    Unplugged MAF - trips "MAF ground fault" CEL, and regains some power
  • Replaced all vacuum lines with quality material from IDparts
  • Swapped my N75 valve with N18 valve, zero change. Went to junkyard, grabbed unknown N75 & N18 valves, swapped them in, zero change.
  • Vacuum tested the system and determined it properly holds vacuum. I have applied vacuum to the actuator (w/MityVac) and confirmed actuator rod movement. I did not measure the movement to confirm 3inHg-18inHg.
  • Visually examined my intake manifold. Very little buildup on the walls.
  • Replaced fuel filter.

At this point, I feel like my issues are narrowed down to an actuator, turbo vanes, or a boost leak.
If I'm missing something, please correct me so I can add it to the list of things to check.
I plan on doing the easiest thing first, which is spraying the actuator with WD40 and then looking more closely at it. After that, I feel like the easiest thing is to check for boost leaks.
Is it possible to do a sort of at-home smoke test?
2000alhVW is offline   Reply With Quote
Old September 9th, 2018, 17:18   #2
WildChild80
Veteran Member
 
WildChild80's Avatar
 
Join Date: May 2016
Location: Hampton Roads, VA
Default

I had a boost leak and it was the elbow at the intake right on the bottom

Sent from my Pixel XL using Tapatalk
WildChild80 is offline   Reply With Quote
Old September 9th, 2018, 18:12   #3
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default

The rubber hose that goes right to the ASV?
2000alhVW is offline   Reply With Quote
Old September 9th, 2018, 18:30   #4
WildChild80
Veteran Member
 
WildChild80's Avatar
 
Join Date: May 2016
Location: Hampton Roads, VA
Default

Yup

Sent from my Pixel XL using Tapatalk

Last edited by WildChild80; September 9th, 2018 at 18:31. Reason: There was a good size split on the very bottom of that elbow
WildChild80 is offline   Reply With Quote
Old September 9th, 2018, 21:16   #5
burn_your_money
Veteran Member
 
Join Date: Oct 2012
Location: Kitchener, ON
Default

It's not uncommon for the air duct for the intercooler to rub through the very bottom of the intercooler and cause a leak.
__________________
I buy core TDI pumps. PM me for details
burn_your_money is offline   Reply With Quote
Old September 10th, 2018, 10:13   #6
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default

Thanks for the replies. I am investigating possible boost leaks. Is there a way to 'get at' the intercooler without removing my bumper or similar? I looked through the slats on my bumper and saw the right half of my intercooler fins seem to be packed with black gunk...

I read that one of the signs of a boost leak is oil residue on the outside of the pipe. I'm feeling kinda defeated and confused since I'm finding oil residue all over my engine in odd places.

Should I investigate these areas any deeper?




Also, how bad does my actuator look? I've been trying to test it repeatedly with a hand pump.


I'm trying to get better access to the actuator, and I want to remove the plastic tubing that goes from the accordion'd intake tube (that clamps to the MAF) down to the turbo. It is supposed to have 2 bolts, one on the I/M and the other on the block. Is this pipe one piece or does it come apart half way?
2000alhVW is offline   Reply With Quote
Old September 10th, 2018, 10:21   #7
WildChild80
Veteran Member
 
WildChild80's Avatar
 
Join Date: May 2016
Location: Hampton Roads, VA
Default

The bumper cover comes off so easy, the first time is scary but after you get it off you'll laugh. The hardest part is that clip for the hood pull.

Sent from my Pixel XL using Tapatalk
WildChild80 is offline   Reply With Quote
Old September 10th, 2018, 10:56   #8
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default

Quote:
Originally Posted by WildChild80 View Post
The bumper cover comes off so easy, the first time is scary but after you get it off you'll laugh. The hardest part is that clip for the hood pull.

Sent from my Pixel XL using Tapatalk
You were absolutely correct!
2000alhVW is offline   Reply With Quote
Old September 10th, 2018, 11:10   #9
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default

Got the bumper off and now have an up-close view of my intercooler.

Things may be looking a little hairy at this point.
Methinks it caught a rock and has a hole.
Can someone confirm this?


2000alhVW is offline   Reply With Quote
Old September 10th, 2018, 11:11   #10
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default

2000alhVW is offline   Reply With Quote
Old September 10th, 2018, 11:19   #11
WildChild80
Veteran Member
 
WildChild80's Avatar
 
Join Date: May 2016
Location: Hampton Roads, VA
Default

Was this a northern car? The actuator doesn't look like a prom queen but doesn't look terrible from what I can see. Have you hooked your vacuum pump directly to the actuator and watch how much vacuum it takes to move it and how far it moves?

Have you driven with the windows down and every noise maker turned off and listen for a noticeable hissing?

Sent from my Pixel XL using Tapatalk
WildChild80 is offline   Reply With Quote
Old September 10th, 2018, 11:21   #12
BobnOH
not-a-mechanic
 
Join Date: May 2004
Location: central Ohio
Fuel Economy: 50/45/35
Default

Looks like an old car to me, don't see any reason that thing isn't still intercooling just fine.
Back at Post #1
Quote:
Originally Posted by 2000alhVW View Post
..............At this point, I feel like my issues are narrowed down to an actuator, turbo vanes, or a boost leak..........................
Seems accurate.
What does the actuator do? Are the vanes free? I've seen some creative methods for diagnosing boost leaks.
BobnOH is offline   Reply With Quote
Old September 10th, 2018, 11:26   #13
WildChild80
Veteran Member
 
WildChild80's Avatar
 
Join Date: May 2016
Location: Hampton Roads, VA
Default

Quote:
Originally Posted by BobnOH View Post
Looks like an old car to me, don't see any reason that thing isn't still intercooling just fine.
Back at Post #1

Seems accurate.
What does the actuator do? Are the vanes free? I've seen some creative methods for diagnosing boost leaks.
I'm still working on something to blow enough vacation volume to see, hear or feel it...still at the drawing board

Sent from my Pixel XL using Tapatalk
WildChild80 is offline   Reply With Quote
Old September 10th, 2018, 11:29   #14
2000alhVW
Veteran Member
 
Join Date: Aug 2018
Location: Silver Spring, MD
TDI(s): 2000 Golf
Default

Quote:
Originally Posted by WildChild80 View Post
Was this a northern car? The actuator doesn't look like a prom queen but doesn't look terrible from what I can see. Have you hooked your vacuum pump directly to the actuator and watch how much vacuum it takes to move it and how far it moves?

Have you driven with the windows down and every noise maker turned off and listen for a noticeable hissing?

Sent from my Pixel XL using Tapatalk
Not northern, per se. I bought it from Western MD, but the car is actually in really, really good condition considering. Aside from flaking clear coat, the body is actually mint. Spotless rockers and such. For being a 2000, it actually looks remarkable in terms of rusted fasteners.

I have hooked a vacuum pump up to the line that plugs into the N75. It holds vacuum indefinitely. I think I have possibly found a flaw, but it's still mentally blurry to me. I confirmed the lever starts moving at ~3inHg, but I can't tell if it stops moving around ~13 or not. It seems to move a large distance with each additional pump until ~13in, but after 13, I can't tell if it advances and stays, or advances and then slides back to it's previous position. I'll get under it and look more closely.
Quote:
Originally Posted by BobnOH View Post
Looks like an old car to me, don't see any reason that thing isn't still intercooling just fine.
Back at Post #1

Seems accurate.
What does the actuator do? Are the vanes free? I've seen some creative methods for diagnosing boost leaks.
I'm just suspicious of the localized oil junk. The left half of the intercooler looks pretty good, but the right half almost looks like it got a pinhole in the middle and has been spitting oil.

Have not looked into the turbo at all. Is there some way to see the vanes without a lot of disassembly?
2000alhVW is offline   Reply With Quote
Old September 10th, 2018, 11:37   #15
WildChild80
Veteran Member
 
WildChild80's Avatar
 
Join Date: May 2016
Location: Hampton Roads, VA
Default

Unfortunately the only way to see the vanes is to split the turbo unless you can see them with a mirror with the down pipe off...just not easy period

Use some brake clean and wash the intercooler and see if the gunk comes back or wet it down with water and dish soap and see if it blows bubbles

Sent from my Pixel XL using Tapatalk
WildChild80 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
Low low end power until turbo kicks in and low again on highway. lirunaway VW MKIV-A4 TDIs (VE and PD) 9 February 28th, 2016 15:27
low power alh tdi. none of the normal issues but still low power Gerich@apex-tuning VW MKIV-A4 TDIs (VE and PD) 36 December 24th, 2015 22:44
Need some help narrowing down where to look foodking VW MKV-A5 Golf/Jettas 23 October 28th, 2015 08:05
Narrowing down the vibrations WrEkkED TDI 101 0 April 7th, 2009 15:20
Low power, Low MPG, Low Smoke oguzooz TDI 101 18 November 7th, 2007 22:03


All times are GMT -7. The time now is 00:23.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2018, 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 0.18198 seconds with 11 queries
[Output: 128.38 Kb. compressed to 107.62 Kb. by saving 20.76 Kb. (16.17%)]