C6 A6 3.0 TDI (revs fluctuating all the time)

BrendanM

Registered User
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? The throttle actuator is a fault code I haven't seen before. I cleared all the codes, ran another diagnostic and all the codes above relevant to the manifolds and the throttle actuator remained.

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
 
Top