My passat is no longer mad

[legrandefromage]

this problem seems to pop up alot for VW TDi owners:

Jan 2001 Passat 130 TDI PD engine

Loss of power on acceleration as the boost from the turbo vanishes.

I've replaced the boost control valve and no joy.

The original symptoms were loss of turbo under load which regularly got worse until it disappeared alltogether. It would reset itself when the ignition was switched on and off. Theres no nasty white smoke and the turbo spins up nicely but no boost.

I have a car thats as powerful as a cheese sandwich


anyone found the solution?

 

[Augustus]

From a man that knows.



"My A4 used to do the same. Wastegate pivot wears and the actuator jams occasionaly,usually when you have ragged it for a while. The car will over boost as the pivot jams... ECU gets the hump and cuts all boost as fail safe. When you switch it on and off it resets ECU as it only logs a soft code.

Lube the wastegate pivot with release oil when the turbo is cold and move the wastegate rod by hand to free it up.

Could also be a knackered MAF sensor, but that usually is coupled with consistant poor power and fuel consumption. "

 

[Tallpaul]

Boost leak?

Check for a split hose somewhere. Worth checking the MAF, best way of doing this is probably run the engine with the MAF disconnected and see what difference it makes.

VAG-COM is your friend, shareware version allows basic fault-code diagnosis and a decent lead is about £30, all you need then is a windows laptop.

 

[legrandefromage]

From a man that knows.



"My A4 used to do the same. Wastegate pivot wears and the actuator jams occasionaly,usually when you have ragged it for a while. The car will over boost as the pivot jams... ECU gets the hump and cuts all boost as fail safe. When you switch it on and off it resets ECU as it only logs a soft code.

Lube the wastegate pivot with release oil when the turbo is cold and move the wastegate rod by hand to free it up.

Could also be a knackered MAF sensor, but that usually is coupled with consistant poor power and fuel consumption. "

Ta.

Mine is the later PD engine which is a 8v unit with a variable vane turbo.

 

[alanf]

yep which is even more prone to the problem! the vanes stick causeing over boost and hence the tripping out! I take it this is happening in your taxi? the vanes clog up with carbon due to the constant throttle position and low speeds, it doesnt get hot enough to burn the crap off so it soots up and jams
I know of people that have split the turbo and cleaned it all up and suffered no problems but before you start pulling it apart check all the sensor hoses are ok? no holes or splits? then try the MAF and get the codes read, http://www.ross-tech.com/ down load the freebie version and pick up a cheap lead off ebay

 

[legrandefromage]

yep which is even more prone to the problem! the vanes stick causeing over boost and hence the tripping out! I take it this is happening in your taxi? the vanes clog up with carbon due to the constant throttle position and low speeds, it doesnt get hot enough to burn the crap off so it soots up and jams
I know of people that have split the turbo and cleaned it all up and suffered no problems but before you start pulling it apart check all the sensor hoses are ok? no holes or splits? then try the MAF and get the codes read, http://www.ross-tech.com/ down load the freebie version and pick up a cheap lead off ebay

cheers - theres no error codes showing and no flashy ignition light to tell me 'to take it to ze vorkshop!'

I usually drive the tits off it on my way home to clear the day's low speed driving but not enough I guess.

 

[alanf]

no codes? if it's tripping out the ecu it will hold a code, if its over boost or turbo pressure related? if no code is present? it does seem to point to the MAF, as this degrades over time the ecu adjusts to match the readings and doesnt see it as a fault unless it fully fails or is way out side acceptable measuements, if you unplug it and you get some umph back but it still drives like crap its time to replace it, you can get refurbs IIRC? from GF&S or was it VW themselves? :?:

 

[fingers]

If you disconnect the MAF does it run better? Not sure if this will work on a VW but on some BMWs I know no maf input allows the engine to run better than a buggered maf input...

 

[legrandefromage]

sorry - did get the 'overboost' code so sticky vanes etc looks to be the prob.

 

[Splatter Paint]

I remember this thread from a few weeks back and thought I'd resurrect it, I'm looking to buy a Passat Tdi myself, a 2004-5 estate with 100 BHP, apart from the aforementioned problems is there anything else I should watch out for? I've heard of water in the footwells and injector pumps going, as well as clutches. I'm buying an ex-fleet car with 100k miles on so hopefully most things will have been broken and subsequently fixed!

Thanks

SP