Why is my car hesitating when i press the accelerator and feels like it's losing pressure?

SOURCE: No power accelerating or going up a hill

I have problems with mine too kinda the same this up hills,on ramps and occationally when i put it in park after driving. it sounds like somones in it reving it and letting off i changed the throttle positioning sensor,fuel filter,cut the cat converter off,replaced air filter and it shows no codes anytime i get it scanned i need some advice i dunno what else to do

SOURCE: 1999 VW Passat 1.8 Turbo replaced Suction Pump

If the vacuum pump was a used part did you **** on the pipe to check if it operates correctly,and then there is the throttle plate(accelerator), it needs cleaning as this causes hesitation(remove the fat black pipe on the front right and hold the plate open manualy and wipe clean with wd40 etc, dont use carb cleaner as this removes throttle plate bearing grease) as does dirty air filter, sparkplugs and like you state vacuum hoses.On my passat i replaced all vacuum hoses and clamps as they split after 5 years from heat etc.Dont waste time replacing one, do all.Clean and wd40 your ht leads and clean and inspect the sparkplugs as damp etc causes hesitation.Hows the air filter.

SOURCE: car hesitates and loses power when accelerating

have your mechanic check to see if there is a dirty fuel filter along the gas/fuel line from the gas/fuel tank to the carburettor/injector. It may so happen that there is yet one fuel filter that has been left hidden and never changed even though you have been carrying out routine service and maintenance as at when due in all these while.

as a shortcut, you can also consult the manufacturer to find out how many fuel filters are installed along the fuel/gas line please.

SOURCE: Vehicle hesitates when you accelerate .

The problem was a bad throttle body that was covered by the warranty even with 88,000 miles and 8 being eight years old. Seems like the vender supplied defective throttle body for 1999 to 2002 years.
Check with your local Volvo dealers to get the work done. Should be no charge because it is a factory installed defective unit. I caught the problem before it became a hazard and cause injury or accident because the lack of power or the car stops operating completely while on the highway.

SOURCE: Hesitation upon acceleration

check your air filter, fuel filter and vacuum lines.