About 5000km after my 105000km service my car started to jerk slightly under 3000 revs as if it wasn't getting any fuel. I had all the sensors replaced that the computers picked up as faults [O2 sensor, diesel heating 'gadget?' and the sensor just before the Catalytic convertor]. But it was still jerking with a strange noise to go with it. The computer picks up nothing more? The new mechanic cleaned out the air filter sensor and that worked perfectly....for about 50km then it started to jerk again starting small and eventually so bad the car cannot be driven. I must say it gets worse the longer I drive the car in the day, and at any revs[even 120km/hour, and is also intermittent i.e.: may not jerk at all for a couple of km then all of a sudden she will jerk badly at that speed]. When we are at the traffic light She idles perfectly though! So now it starts getting expensive if you are just guessing and taking your engine apart or replacing injectors just to see if it may be that. The VW mechanic said he has no idea what is wrong and said it may need a software update...would that work if no-one can tell me what is wrong with her? Please help my Girl.;-) [Thanks Sonya]
I assume that by "air filter sensor" you're referring to the Mass Air Flow (MAF) sensor.
If cleaning it helped temporarily, this is usually a sign that the sensor is on its way out and needs to be replaced.
There is one test that you might be able to perform to corroborate that it is in need of replacement. Some vehicles are able to run in a fallback mode in the absence of signal from the MAF sensor, so one quick test to confirm that the MAF is bad will involve disconnecting the MAF to see if it improves driveability. If the driveability improves dramatically, there is a strong chance that your issue is the MAF sensor.