'W' reg Golf GT TDi - Is it turbo or airflow?

[Chunkymunky]

Hi all

Have recently purchased a GT TDI on a W plate on 100k! I am experiencing loss of power problems which are intimitent but very annoying and makes it drive like a 1.1 or sumthing! Any ideas? I scared its the turbo but the garage it convinced its the Airflow management system?:mad: :mad: :mad: :mad: :mad: :mad: :mad: :mad:

[Lex Luthor]

Does it go into "limp" mode, which can be cleared by turning the ignition off then on ?
The garage must be reading fault codes from the ECU. Do you know what they are ?

[Chunkymunky]

When it first started happening and you turned the car off & left for a while it would seem fine & full of power again but it seems to have become more constant and turning it off doesnt work.

The garage is a small operation but as got a whole months warranty out of them will be taking it back 2moz, I fink they r planning to put it into a main garage for a check up.

Its a pity cos the cars a beaut with 18 inc alloys, full leather interior & built in sat nat

[Lex Luthor]

The garage is a small operation but as got a whole months warranty out of them will be taking it back 2moz, I fink they r planning to put it into a main garage for a check up.

It's impossible to maintain these car correctly without electronic equipment like VAGCOM. If you are at all techy you can buy that kind of thing for £70, assuming you have a laptop already.

[tornadored7]

Hi Chunky,

I completely agree with Lex, VAG-COM is an incredibly useful daignostic aid.
(Advance aplogies if I'm teaching you to suck eggs ... :yikes: )

Whenever the Engine Control Unit (ECU) of your car registers a problem/anomaly it will store a Diagnostic Trouble Code (DTC) i.e. a fault code. What Lex is suggesting is that whenever you are losing power, the ECU is storing a DTC/Fault code within the ECU.

The only means of reading the DTC is by connecting a DTC reader, or appropriately equipped PC/laptop to the ECU. For a Golf GT TDI, the ECU connector would be an OBD2 connector located behind the plastic trim, to the left of the ashtray (in the centre console).

Given the widespread availability of laptops, many people use a software package called VAG-COM which enables your computer/laptop to communicate with the ECU, allowing amongs other things the car's hidden cries (DTCs) to be read out.

OK, In a nutshell, with the DTCs read out from the ECU you can isolate the root cause of the power problem more easily. Instead of wasting huge amounts of time, barking up the wrong tree.


(Blue Peter moment) To use VAG-COM you need;
1 To install the VAG-COM software
2 A cable/lead to link from your PC/laptop to the OBD/OBD2 port
3 A very rough idea of how to use VAG-COM


Fortunately, (3) isn't that difficult, since there are many internet posts/downloadable manual for VAG-COM.

(1): Repeating what I've already mentioned in another thread;
VAG-COM is downloadable from http://www.ross-tech.com/vag-com/download/.
(2): A simple VAG-COM / OBD2 cable can be purchased from eBay. The eBay cables won't provide the full VAG-COM functionality, but suffice for simply reading out DTCs. For full VAG-COM functionality, I believe you must purchase a lead/license from RossTech.

[tornadored7]

Firstly I'm not an expert, nor even that knowledgeable. The really knowledgeable people live at http://www.tdiclub.com (http://www.tdiclub.com/).

(To Moderator: I really am not trying to push all traffic towards the USA, but TDIClub is a very good knowledge base).

My advice would be to try and explain the scenario under which you lose power, hence a means of consistently reproducing the problem. Post this into this thread, along with any DTCs that you may have read.

For example, if you are losing power at high speeds, in 5/6 gear (>70 mph), where you accelerate hard then suddenly the engine provides no more acceleration, you are likely to have hit LIMP mode. (The ECU has determined an anomaly/issue, so reduces power in order to avoid possible engine damage, also logging a DTC).

This is likely to be a Mass Airflow Sensor (MAF) issue, or a Boost circuit issue. This is where the DTCs become crucial.

In some (many?) cases MAF issues don't raise a DTC but you can 'feel' a power loss. However I believe Boost circuit issues do generate DTCs.

There is a procedure to test the MAF;

Using (a full version?) of VAG-COM to compare Actual vs Expected Air Mass Flow measured in the ECU
Trying to destroy / REV your engine upto 5000+ RPM (DON'T DO THIS!)

Temporarily disconnecting the MAF electrical connector, and checking whether this improves the power at all.
Substitution with a known good unit (may need matching Engine codes?)My understanding is that the MK4 Golf MAFs (particularly those that aren't made by Pierburg) are prone to failiure (i.e. the B*SCH ones).

(To Moderator: Can I say that without any consequent libel suits?)

[tornadored7]

What you need to do/answer;


Describe the scenario under which you lose power/reproduce the problem (i.e. High speed, hard accelearation, suddenly lose power)
Do you know how old your MAF is, and if it has been changed recently ?
Check whether temporarily disconnecting the MAF's electrical connector improves power (ask if you need a diagram)
Do you have a stock airbox/airfilter or an induction filter ?
Can you update this thread, with your engine code (sounds like AFN), and whether you have a wastegate or VNT Turbo ?
When was the car last serviced (i.e. what condition are the Oil, Air and more importantly Fuel Filter ?)
Are there any DTCs read from the ECU?

[tornadored7]

(To Moderator: Sorry ... a few more links to TDIClub :o)

1) Thread: MK3 TDI turbo dying... remap or hybrid turbo?
http://www.vwaudiforum.co.uk/forum/showthread.php?t=5705

2) Thread: Engine Oil Leaking from Air Intake Manifold to ECU MAP hose
http://forums.tdiclub.com/showthread.php?t=165937

3) Thread: How to troubleshoot low power on an A3/B4 engine
http://forums.tdiclub.com/showthread.php?t=75959

[tornadored7]

// Forgot to mention

From my limited understanding, a Turbo either works or doesn't, but over a period of time it may carbon up (is that really a verb?), slowly accumulating soot and reducing compression.

However the problem as you have described is intermittent, so the good news is that this doesn't lend much support to a damaged Turbo.


A damaged turbo will be permanently damaged, precluding an intermittent fault.
A carbonned turbo may reduce the boost/power, but is unlikely to be intermittent i.e. faulty one minute and fine the next. Nevertheless, I believe that driving the engine hard for an extended period may help to clear a carbonned turbo.