Audi 3.0 TDI (revs fluctuating all the time) 2007 model

[BrendanM]

Hi all,

My 2007 A6 3.0 TDI Quattro continues to force me to spend money on it! It's a non DPF multitronic car with 117k miles.

The inlet manifold problem presented around 18 months ago and after an inaccurate diagnosis by an independent mechanic I was 400 quid worse off and had a new control motor that I didn't need. The problem remained. I replaced the plastic actuator rod on that same bank and it made no difference so I stopped spending money at that point and have put around 20k miles on it since then. The emission control light and the fault codes relevant to the manifold problem have been present ever since.

The second manifold has since played up. No noticeable change in power or economy over the past 18 months.

Another problem has now appeared. The revs are surging/fluctuating all the time (when idling and driving). The needle only moves a fraction but I can hear it and feel it when driving. It's a constant rhythm and rises and falls around once every 2 seconds. It happens even when using cruise control. When standing outside the car with it idling it sounds like the noise of heavy base from the speakers inside the car. In fact that's what I thought it was when I first heard it - my missus drove up when I was standing outside the house and I thought she was playing loud base music. The base type sound is more noticeable when stood at the rear of the car by the exhausts. It literally sounds like the vibration noise you hear when playing music loud with the base setting on high.

I ran a diagnostic using Carista and this is what showed up:


OBD2 - confirmed:
P2112 - Throttle Actuator Control System - Stuck Closed
P2011 - Intake Manifold Runner Control Circuit/Open Bank 2
P2008 - Intake Manifold Runner Control Circuit/Open Bank 1

OBD2 - pending:
P2112 - Throttle Actuator Control System - Stuck Closed
P2011 - Intake Manifold Runner Control Circuit/Open Bank 2
P2008 - Intake Manifold Runner Control Circuit/Open Bank 1

Parking sensors:
01548 - Sensor for PDC Rear Right (G206)

Heater & air conditioning:
00797 - Sunlight Photo Sensor (G107)
00739 - Coolant Pump (V50)

Engine:
P3135 - Intake Manifold Runner Control, Lower Stop not Reached
P1018 - Intake manifold runner bank 2, lower limit not reached
P161A
P161B
P1580 - Throttle Actuator B 1, Malfunction
P106B

Can anyone shed some light on what the fix for the fluctuating revs might be?

I'm considering giving the manifolds some attention again as I really like the car and want to put another 30k on the clock before getting rid of it. I think replacing both manifolds is the only resolution to my problem. I've heard of people buying reconditioned manifolds and fitting them. Has anyone done this? Or can anyone point me in the direction of where I might find a pair?

Thanks in advance for any help folks.

Edited by BrendanM on Tuesday 3rd December 11:04

Edited by BrendanM on Tuesday 3rd December 11:09

[annodomini2]

It'll be Tiptronic, they never built a Multitronic quattro gearbox.

Also the C6, the lower power 2wd V6 TDI is the 2.7, not the 3.0 which comes with the Multitronic box in Auto form.

---

They have an electrically operated throttle body at the front of the engine bay.

It's either gummed up with crud from the EGR valve or broken.

NOTE: If it is gummed up, it's a key sign that the oil separator on the engine breather has failed.

Also your swirl flaps in the inlet manifolds are showing faults, either need replacing or rebuilding.

[shtu]

BrendanM said:

I've heard of people buying reconditioned manifolds and fitting them. Has anyone done this? Or can anyone point me in the direction of where I might find a pair?

Yes. An afternoon's work.

pmg-parts on eBay, you want the "reinforced" version. They used to sell them without the actuator motors (which are never the problem).

Iffy idle? clean the EGR valve out as a first step.