Intermittent Problems Golf 3 Tdi

[golfmk3tdi]

Hi All

I'm new here and I wanted to ask some questions to see if this is anything you guys might have come across before...

I have a Golf Mk 3 TDi and I’m experiencing some weird problems which seem to come and go! When the car is working properly there is plenty of power and it drives great. This is always the case when the engine is cold, which seems to be the opposite of what you would normally expect from an engine! Once it heats up the problems usually (but don’t always) begin.

The symptoms I have when they do occur are:

Low power

Accelerator pedal ‘dies’ (only responds after pumping it a few times)

Brake lights permanently on

On longer journeys, glow plug light flashing and no turbo (limp mode?)

I booked the car in for a diagnostic test but on the day I took it in to the garage – you’ve guessed it – it behaved perfectly and nothing showed up on the computer.


I am trying to coordinate a time when (1). the car is playing up, (2). I have time to take it to the garage, and (3). they have time to look at it, all of which is proving a bit difficult at the moment.

I have a feeling that this is one or more electrical components crapping out intermittently but I can't figure out which ones!

From what I have read so far I think possible contenders are the MAF sensor or Relay 109, and I would be grateful for any opinions on this. Can anyone suggest some tests that I can carry out myself, or even some components to try changing/fixing, or any other ideas as to what may be causing this please?

Thanks in advance for your help.

Mick

[zollaf]

if the brake lights are on, and you are not braking, then i would suspect the switch is faulty or badly adjusted. this will lead the car into thinking you are indeed braking, and could be the cause of your problem.

[golfmk3tdi]

Thanks for that Zollaf - good point! I will investigate this and keep you posted as to the outcome.

Would that problem cause the flashing glow plug light too or do you think there may be another issue as well?

Also I forgot to mention that turning the engine off and on again seems to temporarily cure the lack of power problem, but that was not the case with the brake light - I had to reach down and fiddle about with the switch before it finally went out.

Thanks again for your help

Mick

[Crasher]

Fit a new brake light switch.

[golfmk3tdi]

yes I have already done that - I first noticed the problem with the brake lights yesterday and mentioned it in case it was relevant to the other problems, which it seems it may well be! So far today the car is driving like a dream, but I have a feeling its little foibles may come back soon

[Golf tdi Hal]

This car is probably drive by wire, so if the brake switch is on, the revs drop. Next time the car is running normally, while stationary hold the revs steady at about 3000 rpm then press the brake at the same time. If the revs drop to idle speed, then it's fly by wire and you may have a faulty throttle position sensor, amongst other things.

The ECU remembers faults, so if there was a fault the car knew about, it would have shown up on the diagnostic check.

The low cost thing to do is get down the local scrappie, and start swapping bits over - throttle position sensor, relay 109, brake light switch.....
(don't forget the 109 relay from a scrap car may also be or become faulty).