I am looking to purchase a 2000 W Audi A4 1.8 20V Turbo. I had noticed that after taking it for a test drive and while the engine was still running, there was a sudden cloud of grey smoke from the exhaust at idle?... The seller blipped the throttle and it seem to stop almost immediately?.. Is this something to be concerened about?... Kind regards ... Daniel ..

It is not the left turbo, there is only one turbo. IT is the LEFT turbo intercooler. Looks like a radiator. IT uses coolant from the cooling system to reduce the temperature of the turbo. They are about 100 dollars to apiece. You could drive it BUT if it gets bad you loose all the coolant and must stop or you ruin the whole engine.

Waste gate is sticking.

Most probably your hose is the problem, does the exhaust smoke more than usual ?
If it does then the collapsing hose is reducing the air volume that your engine needs. Your turbo is trying to drag air from the intercooler rad the hose collapses, reduced power.
If you can't get a new one before Christmas try taking off the hose and pushing a hard plastic pipe inside it, if there are bends in the pipe cut the plastic pipe into halves and feed it in. may help. But you really need air into the engine.

could be a hose but it is costly
always check the water and have it pressure tested fast
driving with a leak can empty the sustem and burn the engine

No.It could be the engine need servicing that change of engine oil.

Your mechanic is spot on. The A4's are notorious for turbo overheating and failure. The oil burn is coming in the TURBO itself and then being distributed to 2.3.4 as a side effect. Your not noticing blue smoke because your catalytic converter is doing its job and the minor smoke being generated is being taken care of in the CAT. If you continue to drive as is you will run a certain risk of catalytic converter damage, cylinder damage from fouling (cylinder wash) build up, sludge, etc. If your mechanic has the knowledge on this specifc model there is a way to test the turbo output and turbo heat generation to absolutely confirm. One last thing. in ANY turbo car its imperative to run QUALITY oils not your local wal-mart brand or no name. Many people are not familiar with the demands on a TURBO engine and oil change facilities pull standard oil from 55 gallon drums via a pump.. so you arent feeding your car properly. The AVG (Audi/Volkswagen) company recommends FULL SYNTHETIC and either Castrol or Mobil 1. I have a Turbo Diesel and use Mobil1 as my choice. The recommended oil for your car via their web page is Current Vehicle: Year: 2003 Make: Audi Model: A4 Quattro Engine Type: 4cyl. 1.8Liter Turbocharged
Mobil 1 0W-40
A fully synthetic motor oil, Mobil 1 0W-40 with SuperSyn Technology exceeds industry standards and the major leading builder requirements, enabling the product to keep performing well after conventional oils cannot. Mobil 1 is recommended by leading car manufacturers as initial fill

Check to see if your waste gauge is working properly, it might be wide open.

It needs a turbo.

The oil overfill might well be the cause of the smoke. It will be nothing to do with the overboost. That is quite a common fault and at the main dealers, Audi for me, we usually replace the turbo for that. You need to check the N75 and all the vacuum pipes etc, but when they go you dont get enough boost, when you get to much 99% of the time its the Turbo.

We arent aloud to take turbo's aparts, But In the real word I would suggest you look into having the turbo rebuilt. It is a variable vain turbo and the vains and or the actuator that control them get stuck, which causes this problem. I assume you recently purchased the vehicle, because its very common when its intermittent, for people to see that fault code, know a turbo is £1000 and sell the car.

You can drive around the problem usually, by keeping the revs up. Pulling full throttle from low rpm will bring it on more, thats how we test them.

First off, how the Hell did they issue a DOT Cetificate, if the Emissions are known to be off the clock. Without causing stress, do you have, or can obtain the Emission Test Result Print Out from the Testing Station test Equipment. This is something they cannot refuse. DO NOT AUTHORISE ANY REPAIRS Come back TO ME with your story.
Regards,DT

HI,UNDER EXTREME OPERATING CONDITIONS I HAVE NOTICED THE TURBO TO GLOW RED,SO BETWEEN 800-1500 DEGREES CELCIUS,WOULD SUGGEST YOU LEAVE ENGINE AT IDLE FOR 5 MINS AFTER A HARD DRIVE TO COOL DOWN,ANDY