Polo Losing Turbo at random intervals

TDI I take is turbo direct injection so if that is the case you have a turbo problem or a split intercooler
what ever , the air/ fuel ratio has altered to excessive fuel
the noise could be a blown intercooler hose , split intercooler or turbine wheel in the turbo breaking off
Take it in for a proper diagnosis and have the codes read

Hi the turbo needs to be rebuilt by a specialist they have the required tools and test equipment for the job. When it's built it needs to be balanced otherwise it will break up under high revs. Hope this helps. Regards Jim...

Check the spark plugs, I have seen several VW turbos with this problem. The aluminum heads expand and contract to fast and crack the porcelain on the plug causing the engine to misfire when the turbo spools up and makes boost. The misfire drops the engine and trans into a "safe mode" where it loses power.

ur bacyard mech may hav done things bacward--u need a haynes or some other repair manual/turbo book--scan car using tech II with a data stream for precise solution

In your case the turbocharger is responsible for engine losing power.
The car goes in "limp home" mode!!!
After scan the EDC-15P engine control unit with a VAG or KTS -BOSCH diagnosis tool you will find this: Fault code: P1557-Turbo Boost pressure control exceeded
1. Engine stopped and ignition switch off. Check all pneumatic connections and hoses between turbocharger actuator = pressure unit for boost-pressure control, boost-pressure control solenoid valve, vacuum reservoir, EGR control solenoid valve, intake-manifold flap solenoid valve, EGR valve with throttle - part of intake manifold. Also the vacuum connection between tandem pump and brake booster. If you find something wrong replace parts. If not go to step 2.
2. Extract the hose of the turbocharger actuator = pressure unit for boost-pressure control part of turbocharger. Instead of the original hose you must place another 1 meter long hose with the same inside diameter, and then you check to inspire yourself the air from the other one extremity of this hose. The mechanical connecting rod of the turbocharger actuator must have a smooth and whole motion. If you can do that with your mouth, then you must replace the boost-pressure control solenoid valve. If you can not reach this with your mouth, then you go to step 3.
3. This is the most difficult work. The problem is that the soot particles deposits inside the turbocharger plugging the variable nozzle geometry mechanism = adjustable vanes of the turbine. If the turbocharger actuator is not able to adjust the turbine vanes the charge air pressure increases too much and ECU (engine control unit) goes in "limp mode" = engine protection software. As a result the "limp home" mode engine still running until you turn the engine off (ignition switch off) and back on when the "limp mode" is deactivated, but the fault still remain in ECU memory!
4. You must be able to extract the turbo from the engine and then to disassemble the turbocharger, clean inside adjustable vanes mechanism and refit all.

my 1.9 polo dti revs to 3000 then losses all power and starts to smoke

odd... sounds like the turbo has some sensor built in that cuts it off, do u know if other golfs have something like that? Could be a heat triggered mechanism or a backpressured one? have you modified intake path at all? egs boost controller, Blow off valve, Wastegate, intercooler?

In the VW world it's called "Limp Mode" and unfortunately it's relatively common. Here's a link to some useful info on limp mode

http://www.myturbodiesel.com/1000q_how_to/multi/limpmodetdi.htm

Also check out www.tdiclub.com - these guys know their TDI"s...

check the rubber pipes are not collapsing ,they run from the air filter to the turbo if they appear ok then replace the turbo

Sounds like the car is going into limp mode, and then resuming normal operation the next time you start it. This is probably due to an overboost or under boost situation. If this is the case, the car's computer can't effectively control the boost the turbo is producing, so it just "turns" the boost off. Ask the shop what the engine code was specifically, and then compare it to VW specific codes. ( google "VW OBD codes"). I'm betting the code is either P1556 (boost control negative deviation, underboost), or P1557 (boost control positive deviation, overboost). Proper diagnosis with VW specific software is half the battle. The rest is methodical troubleshooting by you or your shop so you don't replace parts that don't fix the problem. No offense intended, but it sounds like you need to bring your car to a shop that knows VW's. Sorry I'm not more helpful, but without more info, I'm just taking a guess. I've actually had this problem with my Tdi, and the fix was cleaning the intake manifold and a slight turbo actuator adjustment. But, in your case, several things could cause this which is why proper troubleshooting is important. Hope this helps.