Turbo actuator and EGR actuator bypass valve actuator constantly opening and closing, 1 sec cycle.

**big** · 08-11-2015,05:42 PM

Hello,
I haven't been to the forum for a long while. 225K happy miles and counting on my A6 C6 2.7 Avant LeMans TDi

Today I changed the oil and filters and noticed, while the engine cover was off, that the turbo actuator motor is constantly opening and closing and the bypass actuator is also constantly actuating. This was cold and at tickover. It continues to do it when I rev the engine to a higher constant rpm but when I take it for a blast up the road I can't detect any faults. I have driven hundreds of miles this week mainly on motorway.

This thread might be related and useful photo form gupsterg shows the parts in question.
VVT Problem or intercooler?

There we go.
The red and blue marked pieces are constantly moving.

I have a feeling that it might have been doing it for at least a week and the reason I think this is because the engine was "pulsing" on tickover the other morning when I got out to clean the windows. I have driven 600 miles this week and never had a single problem.
The engine management light is on but that was because of the swirl flap issue.

I know you're going to ask for VCDS codes but can't supply since my laptop is upgraded and I need a new version.

Any ideas, without VCDS information?

Thanks, Rob

**gupsterg** · 09-11-2015,05:46 PM

Hi Rob,

It's gonna be your throttle body having an issue.

There are also videos on YT showing same behavior as you describe plus there's a thread on here and ASN where 2 differing V6 owners had same issue.

The throttle body has plastic cog on butterfly, it wears a) due to use b) operating motor is metal cog, which may speed up wear on plastic cog IMO.

You could take it off and inspect it to see if it's sticking/need cleaning, I did do that with mine and found the cog had worn slightly and on occasions manually moving butterfly would stick halfway.

Akash did a "How to..." thread on removal / refit.

All the best
Gup

PS Check out Akash's profile page and select started threads and in one of his threads there's info regarding P/N for throttle. You can buy a VDO made throttle for cheaper than via Audi dealer, the one from Audi will also be made by VDO but with VAG stamp.

**big** · 09-11-2015,06:37 PM

Thanks Gup
I warmed it up and took it for a drive today and all was well. The car drives perfectly, well it drives the way it has for months.
If the throttle body was broken as you suggest wouldn't there be other problems?
The RPM hrdly changes on tickover.

Still working on getting VCDS to diagnose.

Rob

**gupsterg** · 10-11-2015,07:24 PM

First the name "throttle" creates confusion, as generally people think its operation on a diesel is same as petrol and it isn't.

diesel engine does not have a throttle; its power level is controlled by regulating the fuel flow into the engine, thus "throttle" and "gas pedal" are both inaccurate terms when applied to a diesel engine.

The power output of a diesel engine is controlled by regulating the quantity of fuel that is injected into the cylinder. Because the engines do not need to control air volumes, they lack a butterfly valve in the intake tract. An exception to this generalization is newer diesel engines meeting stricter emissions standards, where a throttle is used to generate intake manifold vacuum, thereby allowing the introduction of exhaust gas (see EGR) to lower combustion temperatures and thereby minimize NOx production.

Quotes from Link:- Throttle - Wikipedia, the free encyclopedia

Also google audi euro 5 v6 tdi pdf ssp , then go to page 65, some things in that PDF aren't relevant as that's an SSP for the V6 TDi relating to tighter emissions countries. SSP 350 is the one you'd have, but that doesn't have a page explaining stuff like the other SSP.

**Rob69** · 10-11-2015,08:51 PM

Similar 'throttle' and anti shudder flap on a 1.9 tdi I had, same behaviour as yours until it failed in the shut position. Suggest you change it soonish before it lets you down. Ours drove ok while the flap chattered and no codes logged.

**big** · 10-11-2015,10:03 PM

Gup, you are an absolute star. Thanks.

I thought it worth sharing what I did today. I mended the Throttle Body.

First the fault codes that managed to download. It rather suggests that I have had this problem since July. Entirely plausible because you can only see it and hear it when you remove the engine cover.

004203 - Throttle Valve: Stuck or difficult to move
P106B - 001 - Upper Limit Exceeded - Intermittent
Freeze Frame:
Fault Status: 00100001
Fault Priority: 0
Fault Frequency: 254
Mileage: 337600 km
Time Indication: 0
Date: 2015.04.24
Time: 13:10:46

Freeze Frame:
RPM: 1659 /min
Torque: 198.9 Nm
Voltage: 13.30 V
Duty Cycle: 38.7 %
Duty Cycle: 7.1 %

What I did today was mend the Throttle Body by removing it.
Akash will tell you how here VW Audi Forum - The #1 VW Group Community

Then I took the worn piece of toothed track and turned it over and glued it. This meant that it now meshes with the wheel (which is well worn) that is powered by the motor. I noticed that the metal wheel had not worn the plastic wheel but the plastic wheel is under a lot of load because teh spring which keeps the throttle flap open is very heavy. There is an absolutely amazing YT video in which someone has made their own toothed track and pinion wheel. Throttle Valve Controller Malfunction, 3.0 2.7 TDI VW Audi, VDO STEUERKLAPPE 4E0145950 A2C595129 - YouTube I don't have access to his skill or machines.

Open the top. You can see the worn track and worn small pinion wheel which meshes with it.
IMG_20151110_123700439.jpg

Then I removed the throttle valve and took it all apart (see the YT video) and chipped off the plastic track with a screwdriver until it looked like this. I broke the track but it didn't matter because you're going to glue it together.
IMG_20151110_130752047.jpg

Finally I used araldite to glue back on the track. Turn over the track and glue the good portion of track onto the right hand side of the cam.
IMG_20151110_131715879_HDR.jpg

Re-asemble and replace in the trusty old A6 (225K miles) and it worked.
The turbo and EGR by-pass valve have stopped pulsing every 1 second. Goodness knows how many thousands of cycles it has made in it's broken state but everything seems to be working well now. 200 motorway miles tomorrow will tell.
This evening I fixed my VDCS laptop (pretty good day today!) and cleared down the fault codes. None have returned so looking good so far. I will let you know how long the fix lasts.

Gup, thanks for giving me the clue as to what the fault was. Cheers forumers.