Audi A3 1.8T AGU violent judder/lurch under acceleraration
Posted 21 September 2010 - 08:53 AM
I have Another problem with my Audi A3. Its a 1.8T AGU Engine with 102,000 miles on the clock.
Its hard to explain but it every so often when I accelerate hard from a slow speed the car violently jerks, almost as if I had jabbed the brakes. It feels like the car is trying to stall but then picks itself up and is fine for a while, it also seems to do it when I am only just touching the accelerator at slow speed. It isn't a continous jerk when accelerating hard, just one big sort of "lurch" but when only slightly accelerating it carries on for longer until I accelerate a bit more or change gear. I have only really noticed it in 1st and 2nd gear, it seems fine at high speeds in the other gears.
Due to just buying and doing up a house I cant afford to take it to a garage, my old man who is a retired police mechanic can't figure it out so it's doing my head in!
I have tried various things to sort it, Maf sensor, Lambda sensor, Ignition amplifier module and tested the coil packs but have had no joy! The car is regularly serviced and was serviced approx 6 months ago which included oil, all filters and spark plugs etc.
Any help would be MUCH appreciated!
Posted 21 September 2010 - 11:37 AM
Could try cleaning the throttle body as maybe that is sticking around the closed position?
Have you checked if the diverter valve? Remove it, push the diaphragm up and finger over the small hole on top. When you release the diaphragm it should create a vacuum else it needs replacing. Part number ending 710N is the revised part so if you don't have this one it might be worth replacing anyhow. The DV affects the low boost so could be the cause.
Posted 21 September 2010 - 12:18 PM
I did wonder if it could be the DV valve, would this give randomly occuring problems or would it be fairly consistent? Would it cause a problem when the engine is just ticking over as the car was running rough a few months ago and hasn't really stopped. Also I dont suppose you know if its a drastically expensive part to replace?
Thanks for your reply!
Posted 21 September 2010 - 01:37 PM
Have you had a look for split vacuum hoses. Try spraying carb cleaner with the engine running and see if there is a change in engine revs. If so prob a split. Hard plastic hose between the brake servo and the inlet manifold is a common one to split at joints. Feel around the outside of the plastic joint. Vacuum hoses under inlet manifold can be a cuplrit too.
Could be coolant temp sensor? Do you have black or green one? Green one is the revised part.
Google 'TTweakers guide'. A good pdf for diagnosing 1.8T engine problems...
Next step would be try and get VAG COM and run some tests
Posted 21 September 2010 - 06:31 PM
Thanks for the advice mate, when I get chance I will look into it!
Posted 21 September 2010 - 06:42 PM
Posted 21 September 2010 - 07:46 PM
DV- yes you are in the right place. Large hose in the side of the black cylindrical unit and one out the base. Small vac hose in the top which controls the valve. Takes air from downstream of the turbo and returns it to the air pipe from the filter housing.
Does your engine keep a constant temp?
Posted 21 September 2010 - 07:56 PM
Posted 22 September 2010 - 06:26 AM
Posted 22 September 2010 - 09:08 AM
Wish I could find what the problem is, im gonna check the dv valve when I get chance but knowing my luck it will be fine so will need to keep trying!
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