Vacuum Nightmare!!!!

[Andy9]

Hi all, hope you are all good, i wonder if someone can shed some light!!, ive had a continuous problem with my 04 A4 1.9tdi quattro (170,768mls)for some time now, the problem being lack of turbo boost and a strange airbox noise chatter when coming off the throttle and was identical to (quattro 180's) problem, and basically noise has been doing my head in and just wanted to solve it, anyway to try and solve this i have i started by doing a vcds scan with no fault codes except for engine mount solenoids. i then removed the turbo and inlet manifold and have refurbed my turbo by fitting a new fully balanced cartridge as there seemed excessive shaft play, renewed the vacuum actuator which seemed to stick and degunged the turbo vanes and cleaned the inlet man which was also gunged up, i also cleaned the egr which was also carboned up,(all mileage related i thought) i put it all back together and all this made no difference at all, so i looked at the maf sensor which seemed quite dirty and so i decided to try a new one, the one i bought is not a genuine bosch one and is a aftermarket part and does look slightly different but was assured this is the correct part, i have replaced all the vacuum lines with 3mm silicone ones and inspected the N75 and N18 valves which all looked ok however i did all this to no avail and the car seemed worse, i tried doing the vcds ouput tests and all seemed ok but i decided to replace the N75 valve with a new genuine part, however upon starting the car for some reason the car would barely run and was knocking badly and would only idle for a couple of minutes and then go extremely lumpy and cut out as though it was being starved of air, during this i could hear this air escaping noise but could not see from where, eventially i tracked the air noise to the little BLACK/WHITE one way valve that is fitted inline to the pipe that goes to the brake servo pipe i think (not sure ?), i pulled the vac pipe off this valve and there was a whoosh of air from the vac line so i changed the valve round and this instantly cured the problem with normal idling and all power restored and the airbox noise was GONE!!,all good i thought, i thought i must have put the valve back the wrong way round when i changed the vac hoses however upon checking from various pics on the net the one way valve should have the black side facing upwards and the white side downwards where mine is upside down but the car runs good, upon road testing after a couple of miles i got a eml light on and upon scanning im getting (19586 p3130 egr, regulation range exceeded) upon checking advanced measuring blocks the maf and egr readings are both above and outside the permitted range, where have i gone wrong??, could it be the new maf sensor thats wrong or could is it something to do with this one way being the wrong way round, got to say i'm pulling my hair out (if i had some!!) but determined to solve it, can anyone help and point me in the right direction, any help will be gratefully received, cheers, andy

 

[Darran]

First check your getting vacuum to the egr, remove vac pipe from egr whilst engine is running see if there is actual vacuum., next clean old maf refit then try if no joy then check diaphram in egr is ok if not it has to be n18.

 

[Andy9]

Hi Darran, yeah I think I've might have put a vac pipe back the wrong way round or something, the problem seems to surround this black/white one way valve that goes to the tandem pump, I have mine the wrong way round with the black side facing the N75 valve, having it this way round is allowing air to pass through to the tandem pump is that right ?, I used the car tonight and whilst the car seems to run well the engine management light has come on again and will be the same code as before (19586 3130 EGR regulation range exceeded), about the new replacement Maf off the top of my head if I put the black and white one way valve the correct way round the Maf will be in the correct actual range(don't quote me on that till I have rechecked it again ) but the EGR is to low and the car runs for a couple of minutes then cuts out and knocks badly, the engine won't even rev properly with no power at all, I took the EGR valve off again and cleaned it again and looks generally good, I don't have an handheld vacuum pump so I connected a piece of vac pipe and sucked on it and it did lift the valve and I could hold it open and it didn't seem like the diaphragm had a leak and seemed to close fully when I let the suction off, it's this one way valve that's confusing me, thanks for your help, cheers, andy

 

[Andy9]

Right abit of an update, if I disconnect the vac pipe to the egr when idling there is no vacuum/suction at all and it makes no difference to the engine note when pulling the EGR pipe off, I changed the Maf back to the old one but it made no difference at all, now, if I changed the black and white one way valve around so black side is facing upwards and there is vacuum to the egr valve but the engine starts shaking and knocking badly and engine won't run ??,so I turned the one way valve around so the white side is facing upwards and engine runs fine again but EGR has no vacuum and the anti shudder valve is not working when I turn off engine.
I took the Maf and EGR values in advance measuring blocks while car is idling and Maf specified(230-310) is 465 and the EGR (40-70%) is 84.5% . I also looked at the values in Basic settings with the EGR going on and off and the Maf both remained the same at approx 460 and EGR (ON) 64.5 and (OFF) 19.9.
Ive also looked at all the vacuum pipe layout and according to my Haynes manual they all look correct the only thing that is wrong is this one way valve that is the wrong way round, I'm stumped at the mo and don't know what else to try, andy

 

[Darran]

Its the maf mate, the ecu uses the maf signal to control egr, a high maf causes the ecu to richen the mixture which will cause your problem, get rid of the maf and get genuine part.

 

[Andy9]

ok, but that still doesn't solve the problem surround this one way valve being the wrong way round ? after faffing with the car this morning this valve seems to control alot engine wise and by running the engine with this the wrong way round is somehow altering the boost/vaccum supply to the different components egr, anti shudder valve , tandem pump etc, i used the car today on a short run to work and while i initially thought the engine ran well there does seem to be limited turbo boost and i cant hear the turbo spin up and the car is just not quite right plus the engine management light has appeared again after i deleted it again last night, thanks for your help though, its much appreciated, andy