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i bought this passat in the summer with 134000miles on it a quick oil change and cambelt and away i go however its now on 140000 and the turbo has started to play up when i start driving all is ok, but when i accelerate from 4th -5th the turbo stoppes boosting and it goes along quit happly but no boost,if i stop turn it off and on again all is ok untill i start to accelerate hard again. there is no black smoke at anytime, is there anybody who can point me in the right direction thanks
Edited by Pugugly on 01/02/2009 at 19:56
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Given age/mileage it might be the MFA sensor. Has it started to get better MPG? Don't know if it's possible for you to check it, but they're not too dear to replace. Surprised it's only from 4th to 5th, tho....
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Try removing it and cleaning it (MAF) with an electrical solvent cleaner. Don't touch the inside though. Just spray it.
Edited by Giggles on 02/02/2009 at 13:59
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If its a 110bhp engine it could be the turbo vanes sticking giving overboost which results in 'limp home mode'. Check that there is about 15 - 20 mm of movement in the control rod that connects from the turbo to the vacuum diaphram. If you have the engine on tickover pull off the vacuum tube to the diaphram & you should see the control rod move. Could also be a leak in one of the vacuum pipes that connect to the turbo actuator diaphram & associated control valves. The rubber pipe that VW used then was very poor & perishes. Also it's covered in cotton so you can't always see the split. If it's still got original rubber pipes I would just renew it all anyway as its a possible cheap fix. Replace them one at a time so you don't get the conexions mixed up.
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many thank for your help i got my lad around tomorrow to have a look keep you posted
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If it is the turbo vane mechanism is sticking, here is a link showing how it can be cleaned up.
www.technologie-entwicklung.de/Gasturbines/VNT15-T...l
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If its a sticking vane, why isn't it sticking in the first 3 gears?
How do you know that you have lost boost in the top gears?
Just asking, not trying to be clever.
I have a diesel xtrail, so interested.
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having fault finder check done later let you know the outcome thanks for the interest
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As you say, if sticking vanes they will be sticking all the time.
But few drivers give their engines full beans in the lower gears, so the fault usually only manifests itself when giving it beans in the top 3 gears & then only 3rd if you want the absolute maximum acceleration.
Usually occures between 2500 & 3000 revs when 'limp home' invoked with drastically reduced fuelling.
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many,many thanks for all your help, the fault finder was plugged in and diagnosed boost pressure control switch,this has now been changed and up to now all ok fingers crossed many thanks again
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