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Q: Hesitate on hard acceleration - 2002 Volkswagen Beetle

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When accelerating in to each gear car acts like it wants to go faster then bogs down. In each gear it does this. I have changed the ignition coils and spark plugs also I have changed the air filter and cleaned the mass air flow sensor. It acts like its starving for air when accelerating, but driving slow it's fine.

My car has 186000 miles.

A: Hi there. Check for exhaust restriction and...

Hi there. Check for exhaust restriction and related to that condition of the oxygen sensors (bad sensors can cause catalytic converter plugging).

Another possibility is fuel starvation so the output of the fuel pump has to be tested (pressure and volume) and the fuel filter should probably be changed in any event as preventive maintenance. Check fuel pressure before and after changing filter because in the event filter is plugged, as that will give you additional diagnostic info.

It is also possible to have plugged or malfunctioning fuel injectors. There are some tests of the fuel injectors that can be done on vehicle but it would be most helpful to check secondary voltage patterns on each cylinder on an oscilloscope. That would reveal, in detail, what is going on with the engine. Other easy to check possibilities are vacuum leaks and engine timing advance function. If you need to have this inspected, a certified professional from YourMechanic can come to your car’s location to diagnose the hesitation on acceleration so that this is correctly addressed.

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