Hi there iv got a 2008 fiesta 1.4 tdci f6ja engine... ever since iv had this car its had a slight judder when idleing its only slight buts its noticable also iv recently had an air con service as it was out of gas but when I turned it on my revs was very erratic up and down as if it was exaggerating the idle problem... iv already had my injectors seals done and my injectors checked they are fine iv also changed my oil and replaced my air filter... recently had a diagnostic done and showed up my maf sensor was not working so iv replaced that and check the wiring all is in order but problem still persists... the car itself drives fine and pulls away through the gears no problem but I do get a bit of hesitation when driving slow in low gears so now im swaying towards the fuel delivery...

any ideas and has anyone came across this before?