hi, can anyone tell me what the symptoms are of a faulty n75 valve on a 1.9 tdi (90 bhp) as over the last week my car seems more sluggish on acceleration. The car is fitted with a digital tuning box ,pipercross air filter and elephant trunk mod .It may just be me imagining things .If the valve is faulty, how much are they ?Thanks in advance.

hi, i have the 1.8t petrol and replaced the n75 valve as it was faulty - symptoms were that on acceleration it would boost, then die, then boost, then die again and so on. the n75 is controlled by the ecu which sends it signals asking it to open or close, which in turn adds or reduces pressure on the wastegate actuator, which results in more or less boost. this could be the cause of the loss of power you describe, but you should also check all your boost lines to and from the turbo, intake and n75 for small leaks as this can cause irregular and erratic power loss:thumbdwn:

a faulty mass air flow sensor (MAF) is a more common cause for loss of power on tdi models. but a failed MAF rarely stores a fault code so the best thing to do is get the fault codes read, and a simple rule is 'no power, no codes, new MAF sensor! a common mistake is to disconnect the MAF then drive the car to see if it makes any difference, it wont! a MAF fails in a way that is identical to that of a disconnected MAF. so all you will succeed in doing is confusing things as a disconnected MAF will store a fault code! leading you to suspect it is faulty, but when it is replaced the ecu may ignore the new MAF until the fault code is cleared:( just for reference my n75 valve was around £46 from the stealers i think, and MAF sensors are around £60. if you do replace the MAF, use only genuine as there are some chronically unreliable pattern parts which have been known to fail almost immediately after fitting so be warned. i guess the old saying 'you get what you pay for' comes into play! hth:thumbup:

thanks Ben10, I replaced the maf with a new one (genuine skoda) a couple of months ago so i suppose after checking all the hoses , a new n75 may be on the cards.For the price of a new one i may as well try it and if it makes no difference ill sell it on . thanks again -Dave

so the best thing to do is get the fault codes read, and a simple rule is 'no power, no codes, new MAF sensor!.

Or you could check MBV and actually confirm that the expected and actual figures from the sensor are incorrect.