2.5tdi flat spots

[egesford]

Hi, just got a 2001 quattro sport with AKE engine, its got about 3 flat spots between 1800 and 4500 revs. starts pulling well then backs off a bit then comes in again, is there any common issues with these that might cause this? No fault codes, bit thermostat is stuck open, wondered if this engine holds back when not up to temp or anything. Cheers.

 

[Mike B]

They do need careful timing.Mine was all over the place until the belts etc were changed and timed right by an expert.Obviously it would help to change the stat cos the overcooling doesnt help on a diesel but that means a lot of work on these.

 

[egesford]

Yea, belts need doing anyway so will get that done, service and a remap and see if it's cured. Drove an a6 today with same engine and wasn't much better, probably just expecting too much from it

 

[Greg-S3]

Waste gate weak?

 

[adamss24]

They have a VNT turbo, in stock guise it won't feel too pokey however they have a very flat torque delivery which makes them feel slow when they ain't !

 

[abyrne153]

Might be worth blanking off your EGR valve if not already done as these can become caked with carbon deposits leaving it sticky which could cause flat spots. The EGR problem wont give you any fault codes on the A series engines either and the engine will work very well with it blanked off. Also the VNT mechanism on your turbo can have similar carbon build up and cause flat spots. You can check by undoing the 2 10mm bolts that hold the turbo actuator in place and moving the VNT lever by hand. It should be very free to operate and any stickiness points to it needing cleaning. There are several DIY threads on here on how to do it using Mr Muscle oven cleaner or alternatively the turbo would need to be stripped to clean it properly.

 

[egesford]

Thanks for replies. Egr is next job as it's seems so be spitting out carbon onto the turbo lol

 

[hodgy0_2]

I have a similar problem (same model) - it goes into a pronounced limp mode - at around 40MPH (and accelerating)

really noticeable when pulling out onto a dual carriageway

suspect sticking VNT

I just drive accordingly - been like this for the last 120K - lol