Limp Mode Over 3000rpm

[nhawan]

I have a Seat Alhambra TDi mk2 (2000) that keeps going to limp mode when accelerating hard.

The strange thing is that when on the motorway it goes to limp mode once when I am getting up to motorway speed but turning off and on resets it and then it usually stays ok for the rest of the hjourney.

 

I've read most of threads on this forum and narrowed down the problem to either boost control valve (N75) or the boost actuator near the turbo.

 

I've checked the actuator from underneath the car and can see it move when ignition is turned on and off and when engine is revved.. I cannot move it by hand though. Is this normal?

 

 

The N75 valve is the main thing is suspect BUT for some reason there are 2 of them next to each other!! :(

 

I haven't seen any posts on here mention that there's two of the things...I am assuming thqat the one that connects to the vacuum ball type thing in the front of the engine is the N75 valve.

 

As far as I can tell they both have the same part number..Which leads me to an interesting idea. If I swap them around do you think that could cure the problem?

 

I would be interested to know why I have two boost control valves on my car?

[Guest neil_wiles]

From other posts it would appear that this is also a common result of a faulty throttle pedal sensor of which I have first hand experience and it does exactly what you describe.

 

Check out the pedal sensor it only needs a single track on the potentiometer to be dirty of faulty to cause this error.

[dave_m]

my throttle position sensor (pedal) went recently and it did not go into limp home mode, The revs would just drop to 1100 rpm and the pedal would do nothing whatsoever,

 

The problem described sounds like loss of vacuum to me I had a similar problem which turned out to be a loose connection on the vacuum reservoir (the ball shaped thing on the front of the engine).

 

If you can get the fault codes checked if

 

P1556-Charge Pressure Contr. Negative Deviation is present it is certainly a vacuum loss or a fault with the solenoid itself

[nhawan]

I've checked with vag-com and it says charge pressure control : positive deviation.

 

This indicates overboosting.

 

I've swapped the (Boost control valve) N75 valve with the N18 valve but the problem is still there. I think it may be sticky vanes in the turbo.

Does anyone know if the actuator connected to the turbo should be movable by hand? I tried pushing it but it didn't move at all. It does move when you turn the engine on and off though...

[Masked Marauder]

I would check the pressure sender first.

[Guest SHELLMAST1]

when mine did this we tried every thing and it ended up with the wastegate sticking freed off oiled it up no more probs

[Guest Rigsworth Blows]

when mine did this we tried every thing and it ended up with the wastegate sticking freed off oiled it up no more probs

As a matter of interest, what type of lubricant did you use?

[Rosie]

Check all the vacuum hoses,as a split or hole no matter how small will affect the ECU and put the vehicle into limp home mode.This was the problem with mine and many others on this forum.

[Guest SHELLMAST1]

just blathered it in engin oil

[dave_m]

don't think it will be a vacuum loss problem as the fault code shows positive deviation-vacuum loss would be negative deviation