A6 2.5tdi Quattro 98 power loss and hesitation

[mjpleusch]

so power loss on an A6 diesel question for a change

Hi All,
So still have my problem from before but now at least I know it is not the gearbox.

Essentially the car can no longer accelerate past 3000rpm. It accelerates as normal, then you will feel the power drain away near 3000rpm then smoke will pour out the back of the car, if I continue to hold the accelerator or push it more the car will then dramatically lose power which feels almost like I am pressing the brakes.

Now the car is also hesitating when starting off. I will be in drive and will pull away, the car moves very slowly and then suddenly surges.

I have tried to listen to the turbo and notice that it starts fine and whistles, then there is a strange whooshing noise at higher revs, when I let go the noise goes away and the turbo whisles normally as it winds down.

Not sure if that makes any sense. I connected VAG COM and it reported no faults.

Any ideas much appreciated. Could it be a split in the hose. I was going to look tomorrow morning. Can anyone tell me where the turbo can be found in this engine.
Thanks All

[MikkiJayne]

The turbo is at the back of the engine sitting in the middle of the V. On mine the outlet goes down below the right cylinder head, along the side of the engine, then drops down under the headlight in to the intercooler. Out of the intercooler on the other side, then in to the inlet manifold.

There are a few rubber hoses to come loose in there. When one of mine fell off it ran out of steam at about 3k ish, but it didn't make any smoke because the ecu noticed that there wasn't any more boost.

I think you may have a different problem though since yours is blowing smoke. That means its putting in too much fuel for the air it has. Hopefully someone else will have some ideas about why.....

[adamss24]

You could try disconecting the MAF and if it runs the same or better then the MAF is faulty. I also had a car wich had a blocked cat and i tried everything: new turbo, MAP sensor, MAF, boost control valve, EGR valve, etc. I would remove the cast piece from the turbocharger's flange to the exhaust downpipe. Soak them in lots of wd40 prior to removing, then take it for a spin. If it goes like ****, then its the catalyst...A quick fix its taking the car on the motorway and give it some stick(conect the turbo pipe back first !) and keep the revs as high as possible...Cleaning the turbocharger might also help...

[mjpleusch]

ok thanks will give it a go. dont think its MAF as its only done 70,000 miles and had a new maf 20k ago.

[mjpleusch]

tried the car with maf unplugged but cant tell how it runs as tiptronic box goes into immediate limp mode. the below is what I got after that from VAG COM

VAG-COM Version: Release 303.1


Chassis Type: 4B - C5 Audi A6
Scan: 01,02,03,08,15,16,17,35,36,37,45,55,56

Address 01 -------------------------------------------------------
Controller: 4B0 907 401 K 2
Component: 0000AG D50
Coding: 01004
Shop #: WSC 02325
3 Faults Found:
00553 - Mass Air Flow Sensor (G70)
27-00 - Implausible Signal
00575 - Intake Manifold Pressure
11-10 - Control Limit Not Reached - Intermittent
00523 - Intake Air Temp Sensor (G42)
30-00 - Open or Short to B+
Readiness: N/A

Address 02 -------------------------------------------------------
Controller: 4B0 927 156 BH
Component: AG5 01V 2.5lTDI RdW 9016
Coding: 00000
Shop #: WSC 00000
1 Faults Found:
18265 - Load Signal: Error Message from ECU
P1857 - 35-10 - - - Intermittent

Address 03 -------------------------------------------------------
Controller: 8E0 614 111 A
Component: ABS/EDS 5.3 QUATTRO D00
Coding: 0273004284
Shop #: BB 24334
0 Faults Found:

Address 08 -------------------------------------------------------
Controller: 4B0 820 043 Q
Component: A6-Klimavoll
Note: Excessive Comm Errors

Skipping Address 15-Airbags

Address 17 -------------------------------------------------------
Controller: 4B0 919 930 P
Component: C5-KOMBIINSTR. VDO D06
Coding: 05460
Shop #: WSC 00050
IMMO-IDENTNR: AUZ7Z0W0682899
0 Faults Found:

Address 35 -------------------------------------------------------
Controller: 4B0 962 258 H
Component: Central Lock/Alarm D32
Coding: 04814
Shop #: WSC 00001
4 Faults Found:
01366 - Opened Due to Crash Signal
35-00 - -
01374 - Alarm triggered by Terminal 15
35-00 - -
01370 - Alarm triggered by Interior Monitoring
35-00 - -
00956 - Key 2
09-10 - Adaptation Limit Surpassed - Intermittent

Address 36 -------------------------------------------------------
Controller: 4B0 959 760 A
Component: Sitzmemory D05
0 Faults Found:

Address 45 -------------------------------------------------------
Controller: 4B0 951 173
Component: Innenraumueberw. D03
Coding: 00001
Shop #: WSC 02325
0 Faults Found:

Address 56 -------------------------------------------------------
Controller: 4B0 035 186 B
Component: Radio D02
Coding: 00017
Shop #: WSC 02325
0 Faults Found:

End -------------------------------------------------------

[adamss24]

You either have a blocked cat or a jammed VNT mechanism on the turbocharger and the ECU does not like it. You can clean the turbocharger if you wish and take it from there...Cats are fairly expensive and i would not put an aftermarket one on my car, just genuine ! Good thing is a diesel in good shape does not need a cat for MOT as its there just to reduce smell and NOX...You could take the plastic cover off the engine and scan the engine controller, then go to Basic settings, ch 11 and watch if the rod from the turbocharger's actuator moves smoothly...up and down !

[laskis]

so power loss on an A6 diesel question for a change

Hi All,
So still have my problem from before but now at least I know it is not the gearbox.

Essentially the car can no longer accelerate past 3000rpm. It accelerates as normal, then you will feel the power drain away near 3000rpm then smoke will pour out the back of the car, if I continue to hold the accelerator or push it more the car will then dramatically lose power which feels almost like I am pressing the brakes.

Now the car is also hesitating when starting off. I will be in drive and will pull away, the car moves very slowly and then suddenly surges.

I have tried to listen to the turbo and notice that it starts fine and whistles, then there is a strange whooshing noise at higher revs, when I let go the noise goes away and the turbo whisles normally as it winds down.

Not sure if that makes any sense. I connected VAG COM and it reported no faults.

Any ideas much appreciated. Could it be a split in the hose. I was going to look tomorrow morning. Can anyone tell me where the turbo can be found in this engine.
Thanks All

Hello

I'm Laszlo and one of my friend had same problem as yours.
First remove and clean the manifold air pressure sensor(located at discharge on air cooler) and if it does not help replace the sensor.
Without correct signal of this sensor the max rpm appr. 3000
Cheers
Laszlo