I have a 2001 V70 2,4T wich hesitates when i accelrate, kind of jojo effect, like it's loosing turbo boost??

Turbo is broken,remove repair/replace.Warning:turbo compressor stucked/defect may lead to injecting oil into the piston chamber via intake wich can be fatal for engine (lock it ,as oil can not be compressed and bend the piston rods in the worst scenario).Turbo actuator stucked (small piston near turbo)Clean it/replace.Vacuum leak.(loose/worn tubes,clamps)Need visual inspection.

turbos generate boost fro the heat in the exhaust and the free flow of exhaust gases. That means the amount of fuel through the injectors and blocked cat converter or exhaust system. OK now you know how the boost is generated look for areas that will loose the pressure (boost ) between the turbo and the manifold Look for loose boost hose clamps on the turbo and intercooler and intercooler and manifold. Look for cracks or holes in intercooler. Look for blocked air cleaner as turbos use more air through the air cleaner than normal. Finally look at the compressor blade of the turbo as any bent fin will slow down the turbo wheel giving less boost. Have the turbo tested for correct operation

the turbo has no effect on blower motor performance. you may have a bad turbo but you may also have a bad blower motor or a low freon level on the a/c system.

tubo units get compressor drive power from the exhaust pressure acting on the turbine wheel, not after the turbine wheel so exhaust pipe /flange leaks are non effective
what you problem indicates is a holes in the intake system after the compressor wheel from bad intercooler pipes /hoses loose and or holes in the intercooler
another place of failure is a faulty boost dump valve that is not allowing pressure to build up at all
make sure that the air filter is new as any restriction is a problem
of course you could always take the car to an accredited turbo repair shop and just talk about it and get information as to the possible problems

the turbo boost sensor is on the intake manifold and can be replaced
http://www.citydiesel.net/turbo-boost-sensor-24-valve-cummins-p-151.html

bigger is not better when it comes to turbo units as Leyland found out when they fitted a turbo to a 690 diesel that resulted in the destruction of the engines and damage to the company reputation of a reliable engine manufacturer
Subsequent engineering found that a much smaller turbo produced more power without the destroying the engine
The turbo fitted to the engine originally is the correct unit for the maximum power that the engine mechanicals can handle
What you have to do is to ensure that the variable vanes of the turbo are working correctly and there are no boost pressures lost from intercooler leaks and loose hoses
Run the fault codes to determine sensor and actuators for the existing turbo are fully operational

FocalJet.com

you may be going into over boost at which the computer cuts the fuel check out dawes devices .com they make an over boost eliminator for like 40 bucks

There may be a loose or split intake (Boost) hose.
You may need to have boost pressure checked.
The transmission kicking down may also be caused by low boost pressure as the transmission receives boost pressure, to regulate shift pattern.
Hope this helps.
Regards MMP

Hi, the only real way forward is to get the fault codes read from the on-board diagnostic system. In the meantime, you could check for clogged /loose / fallen off vacuum pipes and splits in the intercooler pipework.

Hope this helps. If this "fixes ya", I'd appreciate a rating for my reply, If not, please delay the rating and add a comment with any extra info you have and I will try to think of something else.

Cheers, D.