passat pd 130 limp mode

[reggaboy]

i have the limp mode problem. from cold boosts fine until warm then if under load turbo suddenly turns off. restart sorts it for a minute then bang, gone again. also, once the tick over jumped up to 1200 when i was sitting at the lights. code is low boost pressure or something. have pulled plug off the MAF but it just drives with no boost at all, am told this means the MAF is good.

can't find any vacuum leaks, car does whistle but told this is normal sound for these. understand the VNT should open 3/4 inch, but how do you check this, how can you see it? and there is a N75 valve? is that right, and where is it, what does it look like, how do i check it etc? can anyone tell me the other possible causes and where these thing would be on my engine. passat 2001 tdi 1.9 pd130 dont know my way around it yet. i am in essex anybody know a good place to take it. cheers

[PDMaster]

The N75 valve is the one with the grey top, I think it is mounted on the front of your engine, left hand side in front of the round "pressure sphere".

Whistling is normal, it is the turbo spinning "wind noise" as it were in the pipework.

Easiest way to check the N75 is to change it for another one!!

If you have VAG COM you can do Final Control Diagnosis on it, and it should click, but this does not always give a true result as I have earnt from experience.

It is work trying the MAP sensor, they get clogged up with oil now and again, does it do it at the same temerature each time? Perhaps the water temp sender.

Really needs to be Diagnosed with Vag Com or some other diagnostic tool first.

What do you mean "code is low boost pressure"??

Tony

[reggaboy]

thanks for the help.

dont have VAGCOM, but macanic put it on some tester and said it came up with fault "low boost pressure".

not sure about the MAF. have been told that if MAF is faulty and you pull off lead, car should run with full turbo boost, but have read that it should run with the same or a little bit more boost. do you know which is right? mine has about the same power when i pull off lead. dont want to spend £80+ if its not that.

i do hear a click when the turbo should be coming in so maybe N75 is ok.

can you tell me where the MAP sensor is and what it looks like?

car normally does it when up to operating temp and under load, but if i really put my foot down going up hill, it will still do it when engine is cold.

many thanks