looking for some advice my vrs (petrol) wasent running to good and was coming up with various fault codes so i replaced the airmass sensor with a genuine bosch replacement the car runs so much better now

i am now having a problem where the car flags up a code relating to a pressure drop beteen the throttle valve and turbocharger. it only ever occurs on motorway driving where the accelertator peddle is slighy depressed and the ecu sees the drop and cuts off the boost untill i restart and all is fine again.

the only thing i can think that could be causeing it is the bailey dump valve but it only started after i replaced the air mass . could the ecu be picking up the fact that the boost isent getting reculated into the air intake pipe or is there any othere common faults

thanks

steven

is it remapped? Could be a duff map sensor or could be a boost leak, have you checked all the boost pipes?

Try checking the intake manifold pipe

they are known to mess the boost up

Edited 19 March, 201115 yr by philiow

yeah i replaced some of the pipes on it as they had cracked The car was mapped as well think i am going to get a smoke test done on the intake system to see if there is any leaks that i cant see

Smoke test?

Smoke test?

Basically allow the car to ingest smoke through the intake, and see if any escapes through the pipework. Wouldnt do this myself on a turbo charged car, as the smoke particles could damage the turbo.

The fault is quiet common, and the usual culprit is the boost pipe from the intercooler to the inlet manifold. The pipe is easily missed, as you cannot see it easily because of its location, on my old vRS when of the joints was leaking air and I got the pressure drop fault quiet a lot until the pipe was changed. Its also possible that the intercooler itself maybe damaged causing the pressure drop.

if its the 17705 and there is no boost leak then it could be a software issue. I had this and the only way around it was to have a patch added to my map to raise the threshold.

I had this on a customers car and spent a long time chasing it. Turned out to be an incorrect airflow meter giving a high reading which meant the ecu was looking for the boost to match it. When I dismantled the airflow meter and checked the bosch pt no it was a tdi one. Car ran fine apart from putting the boost leak code in every day.

Smoke testing is never going to damage the turbo as its done with the engine off :-D and the smoke particles are smaller than what the air filter allows thru anyway lol

Is the Bailey valve a dump valve or a diverter valve? If it's a dump valve, that will be the problem, or at least part of the problem.

Could be that with a dodgy maf, it didn't realise there was a leak because it wasn't registering as much air as it is with the new maf.

took the pipe off that goes to the intercooler from the manifold coulden't see any cracks had to take the headlight out to take the clip off lol. going to go have a word with the guy that done the map was also going to by pass the n75 valve see if it makes a difference i had a golf gti in my work once that was coiming up with a fault and it was the valve that was the cause

steven

The dreaded 17705 code!!!

Could be so many things, & can be a nightmare to track down. In your case I would try unplugging the MAF, go for a run & see if it throws the code. Bailey DV is often known to cause problems on VAG 1.8 T's, but if the car ran fine with it before it's probably ok. The small pipe that goes into the DV can often split, & be hard to spot, also all the pipes under the inlet manifold are prone to splitting. I had the 17705 code on my old mk4 Anniversary, after remapping (Custom Code stage 1) which turned out to be incorrect values in the software.