ok so a mate brings me an A4, says its down on power, says he wants me to change the turbo, so i swap the GT15 for a GT17 as thats all i had knocking about, anyway the problem is still there, infact he says its much worse, its realy slow to rev, like it takes about 5 seconds to reach the red line wen reving in neutral, any ideas? i thort it cud be a boost leek but surly it wud still rev? cud be a colapsed cat but it runs the same with no down pipe, is there a sensor or vacuum pump that could cause this? why would it be worse with a GT17 i thort it would be better?
im out of answers, dont know much about the controls around the AFN, if anyone can help would be greatly appreciated
Seems MAF-ish to me. Is AFN like a ALH? Sorry I don't have any more helpful advice.
its 1Z, early TDI
why would having a better turbo make it slower?
I agree, sound like a mass air flow sensor problem. The reason the GT17 would make less power is because a turbo spools up and makes boost based on how much exhaust is going through it. With a small amount of exhaust going through the manifold, the GT15 would actually spool up sooner and make more boost than the GT17. If you have a faulty MAF sensor the computer will only recognize a small amount of air going into the engine, so it will only allow your pump to inject a small amount of diesel. It's almost like you are giving 1/4 throttle.
Is the MIL light on? Do you have a scaner to check for codes? A faulty MAF sensor won't always set a code but if it does, then you know for sure that is your problem. Hope this helps, with out hearing or seeing the vehicle its hard to diagnose.
Cheers.
Throttle position sensor mis reading?