Hi Guys,

Hitting my head against a wall with an EGR issue on my 1.9TDI 4 Motion with an AVF Engine. It all seemed to start with a refill of fuel from a certain supermarket but I've emptied it all and refilled with no improvement. VCDS tells me nothing. No error codes. I'm finding that at light-med throttle loads between about 1700 and 2500 RMP I get some hesitation and a considerable amount of smoke. Flooring it clears the smoke. Through substitution with my daughters car I've eliminated the N18 valve. The wiring to the N18 is solid. All the Vacuum hoses are sound - tested with a hand pump. I've reluctantly just put a new EGR on it to no avail. If I disconnect the EGR vacuum hose it runs perfectly but after 20 odd miles I get an emissions workshop light.

I've put a vacuum gauge in parallel with the valve and watched it whilst driving and the gauge is very erratic whilst this hesitation is going on. Something is clearly telling the N18 what to do and it isn't good.

I've done the VCDS 3rd gear acceleration tests to check the MAF sensor/ boost pressures actual-versus-expected and all look good.

I'm sure there are a bunch of you thinking "delete the EGR" but a) I'm not sure how you'd do that without getting the emissions workshop warning and b) I hate to let things like this beat me.

Anyone have any experience in this area? Id love to hear from you. Car has 210K miles on it, pulls like a train and uses no oil. I put 170 K of those on it and apart from a split turbo outlet pipe split I've never had any engine woes until now.

Suggestions gratefully received.