I have had the annoying occasional hesitation/missfire around 1700-2000 revs ever since I bought the car back in April. I have done the usual things like replace the EGR and boost sensor but it still occurs. I was going to re-wire the number 3 injector next but havn't got round to it.
Anyway the other day I needed to repair my airbox as some of the bolts holding it shut have stripped the thread. I removed the airbox and put some superglue in the thread holes so there was something for the screws to bite on. While it was out I had a look around the area and noticed a metal box which looks like and ECU down below the drivers side light, behind the bumper. I gave it a wiggle and then put the air box back and re-pugged the MAF lead. Ever since doing this the hesitation has gone. So I am not sure if it is related to removing and replacing the MAF connector plug or whether touching this ECU looking box and creating a better connection. Or it could be one of the wires in the loom that was disturbed when I had to unclip them from the side of the airbox.
Its may just be a coincidence or maybe I have stumbled across the cause of the problem.
Its now been 3 days without any re-occurance. So fingers crossed its gone for good. If it does return I will try to get to the metal ECU style box from under the bumper and try unplugging it and replugging it as it could be a dodgy connection. Or it could just be the MAF connection which is even easier. If its something to do with the wiring loom then????
Perhaps one of the many sufferers of this may want to try disconnecting/reconnecting the MAF cable and see it that makes a difference for them.