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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.

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Old November 4th, 2019, 07:53   #1
kraftwerkturbo
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Location: Brighton, MI
Default BEW - no boost - used turbo

I replaced my turbo with a used identical one (very tight, lever moving).
Reused my actuator (tested, not leaking).
After installation, car runs fine, no leaks.
I can hear turbo spooling (straight exhaust from turbo back).
But no (ZERO) boost.

Only 2 codes (same as before):
17524 - Oxygen (Lambda) Sensor Heating; B1 S1
P1116 - 000 - Open Circuit
16955 - Brake Switch (F)
P0571 - 000 - Implausible Signal - MIL ON

Any suggestion what to check/test/troubleshoot to find out why I don't have any boost?
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Old November 6th, 2019, 13:21   #2
kraftwerkturbo
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Ran output test with VAGcom. Changes sound and N75 duty cycle, I assume as it should.
Tested the actuator on the turbo, holds vacuum. Lever/actuator moves when applying vacuum.

Any suggestion what next to test to find the cause for zero boost?
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Old November 6th, 2019, 15:31   #3
wonneber
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Did you check for boost leaks?
I sprayed mine with soapy water and found a crack in the plastic tubing.
BEW's also have a problem with one of the clamps coming off (slightly?) and loosing boost.

When you swapped the actuator did you work the arm going into the turbo to see if it moved full range, easy, and smooth?

How much vacuum is the pump producing?
Is it getting to the actuator?
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Old November 14th, 2019, 15:06   #4
kraftwerkturbo
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Quote:
Originally Posted by wonneber View Post
Did you check for boost leaks?
I sprayed mine with soapy water and found a crack in the plastic tubing.
BEW's also have a problem with one of the clamps coming off (slightly?) and loosing boost.

When you swapped the actuator did you work the arm going into the turbo to see if it moved full range, easy, and smooth?

How much vacuum is the pump producing?
Is it getting to the actuator?
If I had LOW boost, i would think boost leak. But NO boost?
Turbo was VERY tight (I'd say like new, have seen my fair share of turbos), actuator arm moved freely full range (also moves when hooking up vacuum hand pump at N75 hose).

Boost pressure: logged today, with 'pedal down', I actually see (on gauge) and measure NEGATIVE boost. VAGcom atmosphere was arounhd 950 today, boost under WOT is 800 or so (i.e. negative boost).
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Old November 14th, 2019, 15:09   #5
kraftwerkturbo
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Removed charge pipes to intercooler, and intercooler itself (still some oil from blown turbo). Cleaned.
Tried again today, no difference.


Logs confirm that N75 is ‘acting’ (low duty cycle and max duty cycle (95%).
Also requested boost is present (1750 mbar, tapering to 1550 mbar in log).
Boost is zero. Actually, boost goes negative (manifold pressure lower (down to 800 or so) than atmospheric pressure (950 today) when putting the pedal down (also confirmed with boost gauge).

I then measured vacuum (with my mitivac) to N75 (around -20 as it should, no other symptoms of ‘poor vacuum’ like bad brakes for example) and from the N75 to the wastegate actuator (also -20 as it should).

Not sure what else there is to check/try. Any suggestions?
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Old November 14th, 2019, 15:16   #6
Mike_04GolfTDI
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Any chance the MAP sensor in the intercooler isn’t working? Maybe there’s boost but the computer can’t see it.
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Old November 14th, 2019, 15:17   #7
kraftwerkturbo
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emoved charge pipes to intercooler, and intercooler itself (still some oil from blown turbo). Cleaned.
Tried again today, no difference.


Logs confirm that N75 is ‘acting’ (low duty cycle and max duty cycle (95%).
Also requested boost is present (1750 mbar, tapering to 1550 mbar in log).
Boost is zero. Actually, boost goes negative (manifold pressure lower (down to 800 or so) than atmospheric pressure (950 today) when putting the pedal down (also confirmed with boost gauge).

I then measured vacuum (with my mitivac) to N75 (around -20 as it should, no other symptoms of ‘poor vacuum’ like bad brakes for example) and from the N75 to the wastegate actuator (also -20 as it should).

Not sure what else there is to check/try. Any suggestions?
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Old November 14th, 2019, 15:46   #8
BobnOH
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Is it possible the ECU tells the car no boost when brakes are applied?
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Old November 15th, 2019, 05:36   #9
kraftwerkturbo
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Quote:
Originally Posted by Mike_04GolfTDI View Post
Any chance the MAP sensor in the intercooler isnít working? Maybe thereís boost but the computer canít see it.
a) Would throw code if MAP were unplugged/not working.
b) Boost gauge shows exact same behavior (including "negative" boost when putting pedal down).
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Old November 15th, 2019, 05:40   #10
kraftwerkturbo
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Quote:
Originally Posted by BobnOH View Post
Is it possible the ECU tells the car no boost when brakes are applied?
Not sure, never tried.

Pretty sure (on most drive by wire Audi/VW) that ECU cuts throttle when brakes are applied.

My logs show requested boost at at 1750 mbar or so tapering to 1600 mbar (but actual boost falling from 950 mbar (ambient pressure) to 800 or so.

So ECU definitely WANTS to boost.
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Old November 15th, 2019, 05:42   #11
kraftwerkturbo
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Possible that wastegate actuator (the 'stop' set screw on the turbo, the actuator arm nut/rod) are so out of whack that it won't boost?

I did NOT change the setting on the turbo set screw, and I tried to maintain the position of the lock nut on the actuator arm.
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Old November 15th, 2019, 06:02   #12
oilhammer
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Just to rule this out, replace your brake light switch. These are a common failure (many cars were recalled... some were RErecalled). They are cheap, easy, dealer has them on the shelf, and they come with an instruction sheet (worth the read, as they only install once and self adjust once).

Know that this switch has dual circuits, so the brake lights may not be malfunctioning regardless.

Once we know the ECU is getting the correct brake switch input, then we can concentrate on your turbocharger. Because right now, you have no boost DTCs, because it looks to be the ECU isn't calling for any boost... likely because it thinks your foot is on the brake pedal.

The oxygen sensor fault may end up being a red herring and need to be tuned out. But that will not cause a low power condition anyway.
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Old November 15th, 2019, 06:35   #13
kraftwerkturbo
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I had (before changing turbo) and still have the brake light switch code.
Replaced (with dealer part) still getting code. Gave up a few years ago, bin driving with code ever since.

16955 - Brake Switch (F)
P0571 - 000 - Implausible Signal - MIL ON
Freeze Frame:
RPM: 840 /min
Torque: 64.0 Nm
Speed: 0.0 km/h
Load: 0.0 %
Voltage: 14.29 V
Bin. Bits: 11101110
Torque: 158.0 Nm
Bin. Bits: 0 01 0


Readiness: 0 0 1 1 X
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Old November 15th, 2019, 09:22   #14
JB05
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I too get a brake light switch DTC, but my turbo works the way it should. The dealer replaced the switch per recall many years ago. I do have a Garrett smart actuator after the KP39 actuator rusted out internally. Had Malone do a VNT delete to accept the new actuator. I also changed the N75 because it had sucked up a lot of the rust from the old actuator.
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Old November 15th, 2019, 10:53   #15
Tdijarhead
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Are you driving this and getting no boost or are you trying to get boost just sitting in your driveway pushing on the go pedal?
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