davidpenman Posted January 13, 2007 Report Share Posted January 13, 2007 Further to my previous post, thought I would add some further info. When cold, the engine is very reluctant to rev past about 2,000 rpm - as if either the turbo isn't spinning up or no fuel is getting through. Once warmed up, the car will sometimes be fine and go like a rocket but other times will either simply stop accelerating at about 3,000 rpm (exactly the same effect you get when you hit the rev limiter). Other times if you are accelerating at half throttle, the acceleration is lumpy to say the least. Apart from the stopping accelerating mainly occurring in 1st and 2nd gears, the problems are basically random. A further bit of info is that if you accelerate hard, when you change up a gear, if you hold the clutch in and let the revs drop to idle, just before they get to idle there is often a funny sort of screeching noise (my initial thoughts were this might either be the turbo itself of a dump valve/wastegate?). You can also sometimes induce this noise at standstill by revving the engine to 4,000rpm and releasing the throttle - the noise occurs just before the revs fall to idle. A VW and an Audi dealer have both found no fault codes on their diagnostic machines - do they not use VAG.COM? Having read some other threads on this forum (which is fantastic by the way) today I disconnected the MAF. The ABS and an engine warning light were displayed but the car ran. It drove very smoothly and I could not induce the screeching noise. The only difference was that it felt flat all the way through the rev range, but revved smoothly (it felt suffocated - is this normal with the MAF disconnected?). When I reconnected the MAF, it revved much freer when it was having the problems above, but the screeching noise was also there on occasion still. Would this mean the MAF needs replacing? Any ideas what the screeching noise (it is mechanical sounding and definitely not the engine itself or an air leak in any of the turbo pipes) - could it be the dump valve? Link to comment Share on other sites More sharing options...
kite Posted January 13, 2007 Report Share Posted January 13, 2007 Not sure if the turbo is VNT But could the nozzle be stuck, this would cause the turbo not to produce the right amount of boost. MAF's are exchange from bosch. In the VAG con section there is a list of people who have the tool. Maybe theres someone close to you who could scan the car. Link to comment Share on other sites More sharing options...
davidpenman Posted January 13, 2007 Author Report Share Posted January 13, 2007 Could you please explain what you mean by VNT? Also, when you say MAFs are exchange from Bosch - is there somewhere else I can get them (OEM) cheaper than Audi? The boost pressure is fine according to the dealers ! I will see if there's anyone local with VAG.COM - thanks for the pointer. Link to comment Share on other sites More sharing options...
kite Posted January 13, 2007 Report Share Posted January 13, 2007 VNT= variable nozzle turbo MAFs are exchange from bosch dealers, not sure about dealers Try these people http://www.vagparts.com/ Link to comment Share on other sites More sharing options...
davidpenman Posted January 13, 2007 Author Report Share Posted January 13, 2007 I believe the turbo is variable vane, but not sure about VNT. Any idease what the noise could be? Is is possible the turbo is overboosting if the MAF is faulty and causing the dump valve to make a noise? Link to comment Share on other sites More sharing options...
kite Posted January 13, 2007 Report Share Posted January 13, 2007 Ahh varible nozzle turbo. Don't think they have a DV. The idea of VVT is the vane changes pitch so as not to over boost. I think the vanes are operated on a rod that has been known to stick, not sure of its location. Could the screeching be a slipping belt. Link to comment Share on other sites More sharing options...
davidpenman Posted January 13, 2007 Author Report Share Posted January 13, 2007 The plot thickens - if there's no dump valve. I don't think it's a belt for 2 reasons - first, the screeching noise disappears if I disconnect the MAF electrical connector and secondly, it sounds more mechanical (I just wish I could describe it better). I think I may have found someone with VAG.COM so might be able to hook it up next weekend. I will try and remember to post how I get on. Thanks for your help so far - much appreciated. Link to comment Share on other sites More sharing options...
kite Posted January 13, 2007 Report Share Posted January 13, 2007 My car has the same engine. please keep this going to let us know the outcome Link to comment Share on other sites More sharing options...
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