sharan overboosting

[sharan888]

right, got a big problem with a sharan that im hoping you guys can help with. ive spent a while on it now and havent found the problem.

its a vw sharan. 1900tdi. engine code - avg. it isnt a pd engine its the old style. v reg

i own an engine reconditioners, we had a vw sharan come into us for a full recon engine a week ago. the engine had dropped a valve and done lots of damage. so, rebore, new pistons, new head, new injector later it was back up and running. i went up the road and it didnt feel right. there wasnt much boost.

took it back, and while the vehicle was stationary i revved it. as i got towards the redline i let off the accelator and there was a big flutering sound coming from the airbox as the car returned to idle. i would discribe the sound as wastegate chatter, like a rally car.

i noticed a hissing sound while driving, after a bit of searching i took the ecu apart and found a split vacuum hose. which i was told would cause the overboosting and this part of the ecu does the altitude sensor and tells how much boost to run.

took it for a run and it had the same problem.

did some searching and found the variable veins to be a common problem. so stripped the turbo apart and found the sticking problem, cleaned it all up and got them moving freely. i did notice some of the fins had some damage but decided to run with it for the moment to see weather it would cure the problem.

took it for a run it had the same problem.

replaced the maf sensor, had the same problem.

got the ecu tested, its fine.

replaced a valve on the bulkhead(could this be the n75 valve you gys mention???) was no different.

so, an ideas????????

hooked up a boost gauge and im getting over 20psi on the road.
and about 15psi stationary.

any help would be absolutly great!

[sharan888]

ps...just wanted to add. im not an idiot. ive been racking my brains with this thing for days now. it sounds like ive just been replacing things willy nilly but ive spent ages tracing the problems and then replacing the part i think is faulty.

[VAGMAN54]

thats not bad stationery but low on the road,have you done a smoke test to check that the intercooler isnt holed or a leak on the pipework ?

[sharan888]

its holding boost fine.

is that boost really ok???

i thought 20psi was well over the top. thats like 1.5 bar isnt it?

ive only ever known high performance cars to run that.

i didnt think cars were meant to make boost while sitting still. my skyline hardly had any while sitting still, but was perfect on the road.

[VAGMAN54]

airflow,commencement of injection,needle lift sensor

[VAGMAN54]

yes they boost but dont add the fuel quantity they do that down the road they are ecu controlled,have you disconnected the air mass to see if it goes a bit better,these will have a slight improvement disconnected if its on its way out.....suppose you dont know how it ran before it came in.......where in kent are you ? if its not far from me i am willing to help

[sharan888]

the maf is brand new from vw so that should be ok.

no idea what it was like before it came in, unfortunatly we got it with the head in the boot.

im in ramsgate.

why would the lift sensor affect the boost? surely i shouldnt be hearing wastegate chatter through the airbox though? this means theres too much boost and it cant go anywhere on the over run?

im only going with what all my mates do on there cars. get rid of the dump valve and wind the boost up. the extra air is forced back through the inlet and hit the blades of the turbo.

[sharan888]

also, out of curiosity.

if they boost but dont add fuel, why on my skyline could i hear the dump valve when driving, but not when i was standing still???

[VAGMAN54]

mate i was trying to help your far to negative for me with all the knowledge you got dont think you need helping why ask if you know all the answers ...............if you got overboost you will have that code....underboost a different code ...this is not the skyline forum

[sharan888]

wasnt trying to be negative at all. sorry if i came across like that, i just like to know.

understand this isnt a skyline forum, point taken.