Mk4 1999 Golf Gt Tdi - Mk4 1999 Golf Gt Tdi (110) - Unknown Problem

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Mon 19 Dec 2011 15:54
Mk4 1999 Golf Gt Tdi - Mk4 1999 Golf Gt Tdi (110) - Unknown Problem - Golf GtTdi

I recently bought a Mk4 1999 Golf Gt Tdi and for some reason the car was not accelarating very well. The acceleration was quite poor, nothing what I would expect from a 110 bhp car (wouldnt rev past 3,000/3500 rpm). On the motor way it struggled to get to 80mph and couldnt go further.

I got a diagnostic check and was told there was a problem with: 17957 Boost pressure control valve P1549

The mechanic cleaned the sensor and drove the car whilst it was jacked up on the ramp and it revved up to 120 mph. However driving home it had the same problem of not picking up speed as it should and not going past 80mph (unless down hill, however it slows down when going up hill)

I have had the brakes checked from 'formula one' incase they were sticking but the mechanic said they were fine... I am very confused as I dont know what the problem could be nor do the mechanics and nor does the computer (diagnostics check). CAN SOMEONE HELP PLEASE?????

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Mon 19 Dec 2011 19:29
Mk4 1999 Golf Gt Tdi - Mk4 1999 Golf Gt Tdi (110) - Unknown Problem - injection doc

Oh dear dear dear dear ! I would change your mechanic ! thats not the answer & should never run it up on a ramp to 120 mph with no load.

He was also lucky a drive shaft didnt come apart at that speed on a ramp or the vibration caused by the shafts running at the angle they do cause a wheel weight to come off & worse still kill someone !

Find a mechanic that knows about diagnostics & live data

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Tue 20 Dec 2011 08:34
Mk4 1999 Golf Gt Tdi - Mk4 1999 Golf Gt Tdi (110) - Unknown Problem - cws

As above - you need a new mechanic....

The boost pressure control valve (also known as N75) probably needs replacing, although if you're daring, there are guides on the internet on how to strip/clean them! When you say the mechanic cleaned the sensor, do you actually know what he cleaned > the inside of the unit and/or the pins where the plug goes in to?

Ideally you need someone with VCDS who can do an output test on the N75 valve. Where abouts are you located (as I have VCDS)?

If you do end up needing a new N75, then you can pick them up for £50-60.

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