Thinking of buying an a4 tdi 1.9 diesel - seller says it smokes (grey) under heavy acceleration. Should I avoid it? Or is it livable wth (200k mileage)

The pump needs setting up and timing adjusted.
If you fitted other than Ford injectors, that will also give issues of over fueling.

How many k you have on you clock
sound like it is burning engine oil and diesel
ask you mechanic to check compression on it
If the air cleaner is block it does happen but black smoke
looks like the motor is bad

have the injectors service at a professional diesel specialist shop

Thread: passat 1.9tdi 115bhp 2000 model excesive flat spots - VW ...

www.vwaudiforum.co.uk/.../21982-passat-1-9tdi-115bhp-2000-model-e...
Apr 8, 2015 - Hi everyone I'm new to this forum stuff so if I'm posting in the wrong place about the wrong thing ,pm me and let me know.I've just bought 1.9 tdi passat 115 bhp ... Thread: 1.9 tdi smoking under acceleration
Apr 9, 2015
Thread: 2004 1.9TDI white smoke
Apr 7, 2015
Thread: Audi a3 2.0 tdi flat spot sluggish
Jan 7, 2013
Flat spots in acceleration when less than 60mph in 6th? 2006 TDi ...
Dec 6, 2010
More results from www.vwaudiforum.co.uk

start wih #1,try using a can of redexe/wynns injector cleaner(1 can to 1/2 tank diesel)works well...#2 use 10/40 semi synthetic(best you can afford).i prefer not to use any other fuel additives(other than redexe)as VW group products are susceptical to "clogging"(dirty/high sulphur fuel dont help).i use a can of red every 25k,tailpipe dark grey......

Identifing the smoke color tells you where it is coming from. Black smoke comes from fuel, so it is running rich or not fully igniting the mixture. White smoke comes from oil and often happens under very heavy engine load. On acceleration this could be the piston rings allowing blow-by, on deceleration this could be the valve seals leaking. Blueish smoke is often coolant, indicating a head gasket leak.

You didn't state iof this happens during a moving gear change, or if it has happened since you physically changed some of the gears in the car. On a TDi, I would follow the factory recommendations for all engine lubricants and additives.

difficult to diagnose ,would need to put a pressure tester on radiator and see what happens as white smoke is water vapour,unless its diesel as people often describe white smoke buts its a light grey which is fuel ,although the question does say TDI so am i to assume its a diesel turbo injection ,if it is then to think some more i would need to know if it has an injector pump or if its common rail .because you can have two completely different answers

A4 what? wagon, sedan, quattro? gas, diesel, 4 or 6

Engine also smokes when car driving if turbocharger still faulty. Did you change the engine timing belt (the timing belt kit) meantime? What about engine oil consumption? When engine glow plugs (one or more) burnt then engine exhausts white smoke at idling. Also white smoke at engine idling when water is still present in diesel fuel.

This is very important for Audi 1.9 TDI engine: IT IS FORBIDDEN TO RUN WITHOUT DIESEL FUEL IN RESERVOIR !!!
This type of engine is equipped with pump-nozzle injectors which develop up to 2050 bar injection pressure !
Remove the fuel filter, fill up with diesel fuel and put in place. After that try to start the engine with accelerator pedal to the floor. Heed of electric starter motor temperature and battery status! After 40 - 50 sec. of start attempting wait for 1 - 2 minutes for battery and electric starter motor revival. After few starting attemptions the engine must start.