Very low power after cold start (04 BEW)

arcking

Well-known member
Joined
Feb 15, 2017
Location
Western PA
TDI
2x '04 Jetta Wagons (BEW/09A), '13 JSW
I need some help! After a cold start (meaning that car has both been sitting for a number of hours AND that the temperature is cool - say 40F or below) my '04 with 225,000 miles won't get out of it's own way, even with full throttle applied. As an example of how bad it is, I'm not able make it up a set of standard car ramps without a running start or lengthy application of the throttle. If you stay on the throttle long enough, RPMs will slowly rise and the car comes to life at around 1,800 rpm. At higher RPMs or once the car is warmed up, it has the power it should. This problem has been present for some time - likely for the last 75,000 miles I've owned the car - but it seems to be getting worse over time. I'd appreciate any insight you all might have - I've been through the troubleshooting I can think of, but won't be surprised at all if I'm missing something simple! The car is stock as far as I'm aware with the exception of the EGR delete and upgrade to a VNT 17.

Here's a graph showing the slow response to the application of the throttle - you'll notice that the actual boost is not matching the specified boost, even though the VNT position is reported as changing. I'm not sure what to make of the actual boost not changing in response to the VNT actuator moving - is it typical for the boost to be unaffected by VNT position at an idle? I'm also not sure if the difference in the MAF (EGR) readings is an issue, especially since there's no EGR.



Also to note, when you compare engine torque to the smoke limiter (neither shown in the graph above) once it's warmed up a bit, but still low on power, you'll see that the charted lines are essentially superimposed indicating to me that that's where the torque limitation is - I've been told that the car smokes a slight amount when this occurs, so I think the limitation is legitimate (rather than a result of bad sensor data). I'm not sure if this is the case when it's barely moving though.

What I've done thus far:
  • Check for DTCs - none present
  • Checked vacuum, including between N75 and turbo during operation - they seem to be close to what I'd expect
  • Confirmed that the VNT actuator begins and ends at the desired vacuum levels
  • Checked and adjusted torsion - was -2.5, now +0.5
  • Checked that temp sensors (coolant, fuel, IAT) read similarly - they do
  • Visually inspected all of the charge and intake air plumbing I could
  • Check compression when warm per Bentley - 350-360 psi
  • Tested with and without MAF, including a new MAF (spare)
Since this issue has been present (at least to the best of my memory), I've replaced/serviced the following without effect while addressing other issues and maintenance:
  • EGR & EGR cooler deleted
  • Timing belt replaced
  • Camshaft and lifters replaced
  • Turbo replaced (VNT 17)
  • Lift pump replaced
  • MAF replaced
  • Glow plugs replaced
  • N75 replaced
  • MAP sensor replaced
  • Throttle pedal replaced
  • Applied TSB 07-45 for hard starting
  • Glow plug harness replaced
  • Crank position sensor replaced
  • Coolant temp sensor replaced
Thanks in advance for any help!
 
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DivineChaos

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Joined
Jul 27, 2019
Location
gets cold here
TDI
mk6 jetta sportwagen tdi
Also is your injection timing correct? If it's always down on power. Timing, low fuel pressure. Maybe the pressure sensor is not reading properly. Could also be bad injectors.
 

arcking

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Joined
Feb 15, 2017
Location
Western PA
TDI
2x '04 Jetta Wagons (BEW/09A), '13 JSW
Thank you blueboy7 and DivineChaos I appreciate the help!

How's the fuel pressure at the Tandem pump?
When running, it's fine at the tandem pump test port (tested a month or so ago). I haven't tested at the inlet side (from the lift pump), but if it's good at the outlet I'm assuming that'd be fine. One thing I've considered, but haven't tested, is that the pressure could be low for the initial start but 'pump up' after that - however, the effect on performance lasts far longer than I think that would affect. I'd love to know from someone that's seen low fuel pressure affect their TDI what the symptoms are like - I'm still trying to get my head around fuel vs air for acceleration and power on a diesel with computer-controlled injection. Is there a tell for whether it's a fuel or air restriction that's creating the issue? I'm hoping to pressurize the charge air plumbing today as performance seems lower after I tore that system apart for inspection earlier this week.

Also is your injection timing correct? If it's always down on power. Timing, low fuel pressure. Maybe the pressure sensor is not reading properly. Could also be bad injectors.
Injection should be correct to the best of my knowledge. Since it's a PD, I believe the torsion/kurbelwinkel value would indicate a problem with timing if there were one. Proper tools were used for each timing belt change as well. By pressure sensor do you mean the MAP sensor? I've replaced the MAP sensor (due to a failure) previously. Since the PN didn't match the old one, I pulled the identical match from another BEW to test and the same performance hit was present. That doesn't rule out wiring though.

Would low fuel pressure or a bad injector cause it to run poorly (stumble) as well as low performance? I believe the previous owner may have run bio at some point, so I'm suspect of fuel system issue for that reason, but other than the low power when cold it runs great. I have a run Diesel Purge through them recently with no change.


Here's a graph from this morning (around 40F) - you can see the Engine Torque (pink) following the Smoke Limitation (yellow) almost exactly. It took about 1-1/2 minutes to go approximately 50 yards up a moderate hill to the main road. Also note the huge difference in requested vs actual boost and air flow.
 

DivineChaos

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Joined
Jul 27, 2019
Location
gets cold here
TDI
mk6 jetta sportwagen tdi
Off the wall question here.. what's the exhaust like? If it's plugged it would cause the turbo not to spool. Being the mad is reading properly and you have fuel at least to the hpfp. So either after the turbo is somehow plugged. It's not getting the fuel to spool the turbo. Or the back pressure is to high.
 

arcking

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Joined
Feb 15, 2017
Location
Western PA
TDI
2x '04 Jetta Wagons (BEW/09A), '13 JSW
Off the wall question here.. what's the exhaust like? If it's plugged it would cause the turbo not to spool. Being the mad is reading properly and you have fuel at least to the hpfp. So either after the turbo is somehow plugged. It's not getting the fuel to spool the turbo. Or the back pressure is to high.
I'm all for off the wall questions. An exhaust restriction seems like it could limit power, but I can't think of a reason it'd be dependent on temperature. Would flow through the catalytic converter be affected by it's temperature? I suppose I could test this theory by pulling either the O2 sensor or downpipe.

I have read bio diesel and veggie fuels can clog injectors...
Any ideas on testing BEW injectors? I supposed both flow and spray pattern could be culprits. Of course, it'd be great to have a better idea on their condition without removing them. VCDS shows good balance. (EDIT: When warm)

I'm hoping to pressurize the charge air plumbing today as performance seems lower after I tore that system apart for inspection earlier this week.
To follow up on this, I pressure tested the charge air plumbing and found a leak at the "Lower Intercooler Connecting Pipe" (PN 1J0145834T). I replaced this which fixed the leak, but it did not affect the power issue.
 
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DivineChaos

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gets cold here
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mk6 jetta sportwagen tdi
I saw something on here about replacing the injector cups as a maintance item. I'd either say exhaust or injectors
 

arcking

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Western PA
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2x '04 Jetta Wagons (BEW/09A), '13 JSW
An exhaust restriction seems like it could limit power, but I can't think of a reason it'd be dependent on temperature. Would flow through the catalytic converter be affected by it's temperature? I suppose I could test this theory by pulling either the O2 sensor or downpipe.
I'd either say exhaust or injectors
Well, I pulled the oxygen sensor out and still the same low performance. I'm used to hearing the turbo spool a bit on start on the other Jetta (with a KP39), but didn't hear anything on this one even with the oxygen sensor removed. Maybe part of this is a result of VNT-17 taking more to spool - I'm sure a tune would help, but I'd hate to spend the money on that if there's a another issue. I've done enough driving in limp mode on TDIs to think that this low power level has to be more than just lack of boost.
 

DivineChaos

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gets cold here
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mk6 jetta sportwagen tdi
Well, I pulled the oxygen sensor out and still the same low performance. I'm used to hearing the turbo spool a bit on start on the other Jetta (with a KP39), but didn't hear anything on this one even with the oxygen sensor removed. Maybe part of this is a result of VNT-17 taking more to spool - I'm sure a tune would help, but I'd hate to spend the money on that if there's a another issue. I've done enough driving in limp mode on TDIs to think that this low power level has to be more than just lack of boost.
Do you have spare injectors? Maybe having the larger turbo and not being tuned for it... Or maybe the vanes are broken internally. @oilhammer may have better insight...
 

arcking

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Feb 15, 2017
Location
Western PA
TDI
2x '04 Jetta Wagons (BEW/09A), '13 JSW
Do you have spare injectors? Maybe having the larger turbo and not being tuned for it... Or maybe the vanes are broken internally. @oilhammer may have better insight...
I do not have spare injectors - in theory I could pull them from the other BEW but I'd almost rather buy another used set if that's the route I need to go. I do try my best to avoid the parts cannon whenever possible. Hopefully Brian or one of the gurus will chime in - I wish I had one nearby to have take a look at these issues!
 

DivineChaos

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gets cold here
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mk6 jetta sportwagen tdi
I do not have spare injectors - in theory I could pull them from the other BEW but I'd almost rather buy another used set if that's the route I need to go. I do try my best to avoid the parts cannon whenever possible. Hopefully Brian or one of the gurus will chime in - I wish I had one nearby to have take a look at these issues!
Did you manually test the thing that actuated the vanes? Is it pulling proper vacuume? Maybe something is leaking vac and not allowing the vanes to move to create boost. I'm new to the vw diesel world. Mines got an electric actuator. You could have it idling. And pull vac on the actuator and watch vcds to see if it makes boost.
 

arcking

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Western PA
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2x '04 Jetta Wagons (BEW/09A), '13 JSW
Did you manually test the thing that actuated the vanes? Is it pulling proper vacuume? Maybe something is leaking vac and not allowing the vanes to move to create boost. I'm new to the vw diesel world. Mines got an electric actuator. You could have it idling. And pull vac on the actuator and watch vcds to see if it makes boost.
I've tested the the actuator moves (but not the vanes themselves) and checked for vacuum previously (I put a T in between the N75 valve and turbo). I believe that the value in group 43 is the position of the actuator (since the BEWs have 'smart' actuators, VCDS can read this) and if that is accurate it appears that things are moving as they should per the graphing (but I'm always up for someone to debate that...or any of this!).
 

arcking

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Feb 15, 2017
Location
Western PA
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2x '04 Jetta Wagons (BEW/09A), '13 JSW
I'm still looking for insight on this - any ideas are welcome!

As best I can come up with, there are a few options for what is happening but I'm not sure how to rule these out:
  1. The amount of fuel actually being injected is less than what the ECU believes is being injected (possibly due to a faulty injector or blockage in the fuel supply line in the head)
  2. The ECU is seeing less air flow than there is in reality, thus causing fuel to be limited incorrectly based on the smoke limiter
  3. The turbo is not boosting early enough and thus actual MAF is low and fuel is limited (similar to above)
  4. Air flow is (physically) restricted in some manner

Following up on earlier posts:
  • I confirmed that there is appropriate fuel pressure at the tandem pump test port when exhibiting the low power symptom (rather than when parked) - ~34psi at idle, ~40 psi at ~1150rpm, and ~50 psi at ~1500rpm. I believe that this means it's safe to say that the tandem pump is functioning correctly, but let me know if there's any way this isn't definite.
  • The value I had logged earlier as "VNT Position (%)" was incorrect (43/1 rather than 43/2). Having said that, I confirmed that the behavior of the correct value (43/2) does not indicate any different performance than I'd assumed earlier.
  • As a tidbit for future reference and comparison, I logged boost values while adjusting the VNT at idle on both BEWs using a Mityvac-style pump - neither produced any boost at idle.

For future reference, should anyone want to build a similar charge tubing pressure testing apparatus to the one I used the components are listed below. I put the test plug in the upper intake to manifold hose and used the flexible coupling to attach the 2" adapter and cleanout plug to the turbo to intercooler hose. I drilled a 1/2" hole in the cleanout plug to install the tire stem, and wrapped the threads with Teflon tape.
 

DanG144

Top Post Dawg
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Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
Thanks for the pressure test rig parts list.
I think the plugged exhaust is preventing turbo spool up. The vnt17 will not spool well at low power anyway, but it should be MUCH better than this.
The smoke limiter is based on air flow; if you pull the MAF connector it will use a default airflow and allow more fuel- which IF the exhaust is plugged will only result in more smoke - not much more power.
 

benmarks

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Joined
Jun 14, 2003
Location
Portland, OR
TDI
2004 Jetta GLS Sedan Platinum Gray
Most people here know way more about the mechanical stuff, but I know a fair amount about biodiesel. Have you changed the fuel filter since you purchased the car? I didn't see that mentioned in your notes. What I wonder is if the previous owner ran biodiesel and as it acted as a detergent, wax built up somewhere that it can't escape, and it's still there stuck in your engine (like the filter) and your car is restricted until it warms up and melts the wax, which then hardens again when it gets cold again. This is a TOTAL guess.
 

BobnOH

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May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Thanks for the pressure test rig parts list.
I think the plugged exhaust is preventing turbo spool up. The vnt17 will not spool well at low power anyway, but it should be MUCH better than this.
The smoke limiter is based on air flow; if you pull the MAF connector it will use a default airflow and allow more fuel- which IF the exhaust is plugged will only result in more smoke - not much more power.
Great to have you back!
 

arcking

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Joined
Feb 15, 2017
Location
Western PA
TDI
2x '04 Jetta Wagons (BEW/09A), '13 JSW
At the suggestion of DanG144 and DivineChaos, I pulled the downpipe off today (rather than just removing the O2 sensor, as done earlier) to see if performance improved - unfortunately, it did not improve. I also ran the Basic Settings 11 tests on both cars and saw similar data graphed with regard to boost pressure, but did notice that the car with the KP39 had a slight whistle/whine to it as the exhaust note changed, while the car with the VNT (the troublesome one) did not have the whistle/whine at all.

Most people here know way more about the mechanical stuff, but I know a fair amount about biodiesel. Have you changed the fuel filter since you purchased the car? I didn't see that mentioned in your notes. What I wonder is if the previous owner ran biodiesel and as it acted as a detergent, wax built up somewhere that it can't escape, and it's still there stuck in your engine (like the filter) and your car is restricted until it warms up and melts the wax, which then hardens again when it gets cold again. This is a TOTAL guess.
Thanks for chiming in on the thread and for asking these questions! I have changed the fuel filter multiple times, but it has not seemed to make a difference. Also, since I see the proper fuel pressure on the supply 'rail' (testing at the tandem pump) when the issue is occurring, it seems to me that if there's a restriction it's not at/before the tandem pump (correct me if I'm wrong).

When I got the car (a few years ago), it had a CAT filter setup which I took back to stock. I'm pretty sure the car used to belong to forum member delste (though I didn't buy it from him) and it appears that he did run bio from his postings here. The scenario you describe would seem to me to describe the symptoms, but I don't know enough about the way these cars/engines are put together to be able to nail down where such an issue would be occurring and how to test it - since there's pressure to the supply 'rail', I would think if something like this were to be occurring (and having this affect) it'd have to be at/around the injectors.

I did find a post by @jsrmonster in my research that specifically mentioned biodiesel clogging PD injectors, but I don't know what the symptoms were for injectors in this scenario or whether the material clogging them would be temperature dependent in some manner. If anyone has any ideas, I'm all ears!
 

mittzlepick

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Mar 18, 2001
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union maine
TDI
2004 jetta wagon (365k)2001 wagon tire burner 6spd 2003 wagon(417k)
Mine was a slug for a bit, ignored glowplug code as it still started. Turned out when head gasket started leaking i found ceramic tip glowplug lost a tip beat the piston top to hell and lost 2 vanes off the vnt 17. But compression still good makes a blue victory cloud on startups and goes just fine w 360000 on the clock.
 

arcking

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Joined
Feb 15, 2017
Location
Western PA
TDI
2x '04 Jetta Wagons (BEW/09A), '13 JSW
Camshaft position sensor?
Any particular reason you'd suspect the camshaft position sensor? Any suggested tests? VCDS shows a torsion value, so it's my understanding that it must be working to some extent (along with the crankshaft position sensor) but I can't say how well/accurately.
 

Tdijarhead

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Nov 10, 2013
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Lawrenceville PA
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2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Daughters car, 2005 Golf TDI Mine, all 5 spds
I notice in your first post that your compression test was at 350-360. Diesels are usually at about 450. Were the numbers consistent across the cylinders? If so maybe it was just a glitchy compression gauge.
 

arcking

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2x '04 Jetta Wagons (BEW/09A), '13 JSW
I notice in your first post that your compression test was at 350-360. Diesels are usually at about 450. Were the numbers consistent across the cylinders? If so maybe it was just a glitchy compression gauge.
All readings were within 10 psi. I do have a cheap gauge, but for the BEW engine (per Bentley) when new the compression should be 363-450 psi and the wear limit is 276 psi - based on that, it would seem that all is OK there. EDIT: Tested compression again (this time with the engine was cold), compression is fine per Bentley.
 
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arcking

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Western PA
TDI
2x '04 Jetta Wagons (BEW/09A), '13 JSW
I just know they can be temperamental with all the heat and vibration.
Camshaft sensors or crankshaft sensors? I'm very familiar with issues with the crankshaft sensor (G28), but not familiar with issues with the camshaft sensor.
 
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