Constant Low Power ALH

UhOh

Top Post Dawg
Joined
Dec 24, 2014
Location
PNW
TDI
2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
The way it works makes no sense to me.
At Idle I get more vacuum then when I take off and it drops.
I have power as far as I can tell and the only thing I get is slightly lower MPG for the all highway driving I did for my last 2 jobs.
Use to get just over 50 MPG w/o the AC.
Last several years it dropped varying 45 to 47 or so.
Last job was 1 mile to the highway, 30 miles to the exit (1 toll booth in between) and 1 mile to the parking lot.
I should have gotten 50+
My boost gauge easily goes to 20-23 LB (US) boost if I punch it.
Some day I have to lengthen again, it was even higher when I installed the actuator.
This sounds like the behavior of a MAF that's in decline. My car's FE is starting to taper a bit and I suspect the MAF, original with 166k miles, is getting long in the tooth. I'd ran some logs a while back and things looked good, but I don't trust that it's holding now (have a new MAF I could just toss on to see- might do it at/for my next fill-up).
 

wonneber

Top Post Dawg
Joined
Oct 12, 2011
Location
Monroe, NY, USA
TDI
2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
The turbo is set to 'vent' off the excess boost that the ECM sees that is over allowable boost. So at WOT the more fuel sent into the engine means higher boost so the vacuum drops from the N75 to the actuator opening the vanes in the turbo to help keep the boost under control. The vanes in open position are "venting" off boost like a wastegate setup would.
OK that makes sense.
So if there's low vacuum it is not able to provide boost because it's 'venting' the exhaust out and not spooling up.
 

wonneber

Top Post Dawg
Joined
Oct 12, 2011
Location
Monroe, NY, USA
TDI
2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
This sounds like the behavior of a MAF that's in decline. My car's FE is starting to taper a bit and I suspect the MAF, original with 166k miles, is getting long in the tooth. I'd ran some logs a while back and things looked good, but I don't trust that it's holding now (have a new MAF I could just toss on to see- might do it at/for my next fill-up).
The MAF was changed several years ago 2007-8 or so.
It was the latest at the time the 'C' revision.
As soon as I get VCDS working again I will do a log of boost, air flow, and N75.
When I had to replace the hard drive in my laptop it stopped working.
Thanks for the offer, will get back to you on it. :)
 

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
NEWS FLASH:

Was driving home today and noticed the engine started running louder and had lost power. CEL came on with the following (19561 17552 17849 17957 17660).

I need to verify mechanical timing, but in block 4 the requested timing was 0.4' and actual was 14.6'. Way off and I checked timing with the cahrt and it was way advanced off the chart.
 

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
Okay that problem is fixed, chaffed wire on the anti shudder valve, but still same low power issue.
 

03TDICommuter

Veteran Member
Joined
Dec 8, 2016
Location
So. Cal
TDI
01' NB, 5spd
I need to, the only set I have on hand has a bad nozzle and my brother is almost 2 hours away. But that is on the to do list when I put his FASS on His truck.
Any update? I'm having low power issues that came on about a month ago. Feels restricted/has turbo lag. Was running pretty well and I thought quick up until then. All hoses look good, MAF replaced 4 months ago or so, air filter and snow screen cleaned a few months ago. Not limp mode, I know what that is and this isn't that.
 

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
Still no update, I just moved and am closer by a lot to my brother. I hope to get them swapped out to test. I have also been keeping an eye out for used injectors and none are cheap enough to feel worth buying for a test set.
 

jagster936

Veteran Member
Joined
Nov 8, 2007
Location
Texas
TDI
2002 Beetle TDI Manual
Used alh tdi injectors? I have some from an old engine head that I probably don’t need
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Not likely the injectors are causing constant low power. If they were shot, I'd expect it to run bad.
But I notice the original post was a year and 4 months ago, perhaps we're troubleshooting something else? Did not read all 5 pages.
 

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
Not likely the injectors are causing constant low power. If they were shot, I'd expect it to run bad.
But I notice the original post was a year and 4 months ago, perhaps we're troubleshooting something else? Did not read all 5 pages.
still working on the constant low power BobnOH. I do have a spare IP floating around I may slip on this next winter when my next timing belt comes due, but I figured injectors would be an easy check, just didn't realize it would take so long to get it done :)
 

jagster936

Veteran Member
Joined
Nov 8, 2007
Location
Texas
TDI
2002 Beetle TDI Manual
These aren’t common rail just simple nozzles. Could prob clean them at worst.


Sent from my iPhone using Tapatalk Pro
 

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
Update

Swapped injectors with my brother and no change at least that I could honestly notice.

Also, the catalytic converter has been removed (did it myself) so that isn't the issue (removed it because I thought it might be clogged). Also to check these check inlet temp vs outlet temp with an IR gun and look for a large delta.
 

03TDICommuter

Veteran Member
Joined
Dec 8, 2016
Location
So. Cal
TDI
01' NB, 5spd
I have a spare IP that I'm tempted to try at my next TB change in December.
FWIW, Mine's a dog too. Thought maybe I was crazy and decided to do a 0-60 WOT run. It's like 15 seconds ! It's what tipped my hand into buying an e-Golf, instant throttle response and diesel like grunt.

Drove the TDI to work yesterday (100 miles round trip) and was disappointed the whole time. It's not completely gutless, I still have boost, it just doesn't feel like much until 2500 RPM and even then not so great. The car was much quicker 6 months ago. New N75, N18 and all vacuum lines and still no joy.
 

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
FWIW, Mine's a dog too. Thought maybe I was crazy and decided to do a 0-60 WOT run. It's like 15 seconds !
The car was much quicker 6 months ago. New N75, N18 and all vacuum lines and still no joy.
Did the turbo clean and control ring make any difference?

It seems so weird to not have the power I know it should have...I'm left to thinking it's an IP or ECM issue.
 

03TDICommuter

Veteran Member
Joined
Dec 8, 2016
Location
So. Cal
TDI
01' NB, 5spd
Did the turbo clean and control ring make any difference?
It seems so weird to not have the power I know it should have...I'm left to thinking it's an IP or ECM issue.
The turbo cleaning and replacement control ring was to address 'limp' mode that I would get occasionally when I first got the car. Power otherwise was fine but I couldn't keep the car there for long. After cleaning the turbothe car has been running very well. Felt quick, climbed hills like nobody's business, didn't go into limp mode. Whatever happened started 6 months ago is something new.

It kind of times out to have happened after a fast trip to L.A., cruising 80-85 back and forth including up some decent grades with a lot of throttle.

Dave
 

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
So I did my TB job and didn't have the time to swap the pump and chance it not running so I haven't tried that yet.
Funny thing my brother got an 02 built the same as mine and ours both are more or less the same now as far as power goes. He's going to do TB job and probably swap in a 11mm pump he found on a parts car.
Who knows...maybe it is a pump issue.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Almost surely it's engine management, proly a effing wire or similar simple. A bad IP would run poorly. Have not memorized previous stuff, did you analyze systems with VCDS (or equal)?
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
Didn't you say that system vacuum measured between pump and N75 was 20" Hg at idle? Shouldn't it be higher?
I had a lot of symptoms like yours on my 335d. It turned out to be a worn O-ring pair on the vacuum pump. It was pulling in dirty air whenever I'd get on throttle. The diagnostic trick I used to confirm that theory was:
  1. I noticed dirt tracks leading to the bottom of the vacuum pump and wondered what/why.
  2. I sprayed hairspray around that area.
  3. Went for a test drive and immediately felt a difference.
So my half-baked contribution is:
  • inspect vacuum pump, reservoir, and all vacuum connections closely for dirt tracking that seems to congregate soil near a union/seam/joint, etc
  • test vacuum on throttle by installing a remote gauge temporarily
  • try the hairspray trick
 
Last edited:

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
Almost surely it's engine management, proly a effing wire or similar simple. A bad IP would run poorly. Have not memorized previous stuff, did you analyze systems with VCDS (or equal)?

Yes I did, but honestly don't remember anything too well :)
I don't recall anything being way out. But I could run another log if you have any ideas.
 

ihredneck

Veteran Member
Joined
Dec 4, 2015
Location
Missouri
TDI
2000 Jetta, 2006 Jetta
Didn't you say that system vacuum measured between pump and N75 was 20" Hg at idle? Shouldn't it be higher?
I had a lot of symptoms like yours on my 335d. It turned out to be a worn O-ring pair on the vacuum pump. It was pulling in dirty air whenever I'd get on throttle. The diagnostic trick I used to confirm that theory was:
  1. I noticed dirt tracks leading to the bottom of the vacuum pump and wondered what/why.
  2. I sprayed hairspray around that area.
  3. Went for a test drive and immediately felt a difference.
So my half-baked contribution is:
  • inspect vacuum pump, reservoir, and all vacuum connections closely for dirt tracking that seems to congregate soil near a union/seam/joint, etc
  • test vacuum on throttle by installing a remote gauge temporarily
  • try the hairspray trick
Just for grins and giggles I may rebuild the pump. 20" is a bit low and probably should be closer to 23-25 in-mg. I'll check for dirt tracks too
 
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