hi

ive done a search already and picked up a few peices of info on this, but wondered whetehr theres a definitive list of things to try, cheapest first :-) just to set the scene, ive got a 53 octavia 1.9tdi 90bhp blueline. im a careful driver which probably hasnt helped matters as i beleive you should blast away the cobwebs every now and then, which i probably havent done.

it started a few months ago, just feeling 'flat' as tho the turbo wasnt working. intermittent, some days fine, some days not. in fact it seemed to be every other journey. sometimes even mid journey on constant revs itd just go flat all of a sudden, then maybe go ok again. now its flat all the time.

reading on here and on google, it seems a fair bet the vanes are clogged up, but im not mechnically minded at all. a mate has said it may be the 'boost solenoid' whatever that is.

so....is there a list of things to try? i read that a big dose of redex may help. that right? chuck a load in and try and thrash the engine maybe? then if that doesnt work, a new boost solenoid? where would i buy one of these solenoids from? main dealer or a branch of allwoods maybe? and if that doesnt work what would be my next move?

thanks for any info you can give me.

Cheers

disconnect the vacuum pipe from the n75 valve to the actuator and apply a vacuum to the actuator (sucking with your mouth should be enough). This should cause the acutator control rod to move in smoothly. If it does then the vanes and control ring are probably ok. n75s come from the dealer (or TPS), and I think are around the £40 these days :-( Ideally you need to check the state of the turbo first rather than just changing parts. You can easily rack up a big bill and get no where (which is what a garage will gladly do for you).

A dose of redex won't help, imho. You are better off trying to exercise the vanes on the turbo so use more of the rev range (keep to 2.5k when the engine is cold though).

Check your vacuum pipes for leaks, after the engine has run, open the bonnet and wiggle the pipes about can you hear an air leak? My rigid pipe to the brakes developed a crack/split in the end.

[edit]: Thinking about it might be a failing MAF, unplug it and drive the car (it might cause the engine management light to come on - and log a code, so don't let a dealer con you in the future!). if the car drives better then the MAF is probably better. Get a replacement Bosch or Dealer supplied MAF, don't be tempted with the cheaper ones on ebay.

I spent ages sorting mine out - but mine was a combination of failures, so was harder to diagnose and resolve.

Edited 17 December, 201114 yr by mbames

Thanks for that, very informative :-) unfortunately I know nowt about cars so wouldn't be able to identify a vacuum hose or n75 valve or actuator, the redex is about my competence level :-)

So.... I may have to let a garage loose on it unless it really is simple enough to do with no special tools.

So revving it more will help shift the vanes will it? I'll certainly try doing that.

Thanks a lot for your reply.

Thanks for that, very informative :-) unfortunately I know nowt about cars so wouldn't be able to identify a vacuum hose or n75 valve or actuator, the redex is about my competence level :-)

So.... I may have to let a garage loose on it unless it really is simple enough to do with no special tools.

So revving it more will help shift the vanes will it? I'll certainly try doing that.

Thanks a lot for your reply.

n75 location and MAF:

Once you have tried a drive without the MAF connected, try disconnecting the lower of the left two pipes on the n75 and try sucking on it, with your hand on the actuator of the turbo you should feel some movement. Don't so this when the engine is hot! In order to get your hand on the turbo you can either go under the car, or slide your hand down between the master cylinder (brake fluid) and the EGR assembly.

I would recommend getting the car scanned for fault codes as that might point to a specific problem rather than us taking a bit of a stab in the dark. Where in the UK are you? If you check out the VAGCOM/VCDS list you can see if there is a member nearby willing to scan your car for you.

Once the vanes are sooted up / control ring really rusted up, reving it won't help until it has been cleaned up - here is a whole set of images for when I cleaned up mine.

hi, if you let us know your location then somebody may be local to you & be able to help you out, i had a similar problem on my 90 hp octavia & it turned out to be a split in one of the vacuum pipes, the power steering pipe rubbed on it & eventually wore a very slight hole in the pipe, before you throw money at replacing parts willy nilly & hoping it fixes it,( one of many garages money making schemes) get it plugged in & get the codes read, then post them back so we can help, also im not 100% but im sure there are different turbos on the 90hp versions that dont suffer from the sticky vanes, hope you get it sorted , lee

also im not 100% but im sure there are different turbos on the 90hp versions that dont suffer from the sticky vanes, hope you get it sorted , lee

early 90s have a wastegate, latter ones are variable vane based. Not sure on the cut over point though.

thanks chaps, and thanks for the pics mbames :-)i didnt even know what a turbo looked like!! :-D

im in lincoln by the way, work in gainsborough. ive got a mate who has access to codes, but i think he said it didnt really show anything up. so i think ill suggest to him about driving with the MAF disconnected to try. by the way, is this N75 what ive been calling the boost solenoid? same thing? what does it actually do, and would it show up a code if it needed replacing?

thanks a lot

I would class the n75 as the device which controls how the turbo works, so yes I suppose you could call it the boost solenoid (not really sure that is the proper description though).

If the vanes are sticking, then I would expect an overboost fault to be logged. Can your mate log requested boost v actual boost? If not you need to find someone who can (vagcom/vcds will do this). What fault codes did your mate read from your car? A failing n75 itself won't log a fault, but its failure to work will cause other codes to be generated, such as over- and under-boosts.

I think with your limited knowledge of cars you need to find a good independent garage to take it to who know their VAG cars well. It doesn't sound like anything you can DIY.

I think with your limited knowledge of cars you need to find a good independent garage to take it to who know their VAG cars well. It doesn't sound like anything you can DIY.

Or find some VAG oriented mates haha, that sounds *so* wrong

Or find some VAG oriented mates haha, that sounds *so* wrong

:-D yup, ill let someone else take a look at it i think. best all round :-)

thanks a lot, ill keep you posted.

:-D yup, ill let someone else take a look at it i think. best all round :-)

thanks a lot, ill keep you posted.

No worries, if you get their feedback and specific fault codes, you can feed that info back on here and we can offer our opinions too. I have been there with plenty of turbo issues in the past on my car and I know it can be annoying and very time consuming to track down and fix.

just an update on this problem. as advised i took it to a garage i trust. they replaced the N75 valve, and cleaned and pressure tested the hoses. they got it running perfect. however, they DID say to me it may not have cured it as theres so many variables to possible faults. so they said theyd done £80s worth of work, the cheapest option and hoped itd work. they said if it didnt, it was probably gummed up vanes i think on the turbo, and theyd need it for a few days to fix. at a cost of 5 to £600.

you guessed it :-( at first perfect, but probably 3 or 4 mins into my journey home, at a constant speed, the performance just dipped for a second or so, then back up to normal again. all fine after that, although i had that sinking feeling that it wasnt fixed. next journey, 20 miles, fine. return journey, car felt flat again, no oomph to it :-(

since then its been intermittent, just like it was when it started showing this problem. some journeys fine, some 'flat'.

i dont understand enough about cars, but it does baffle me that if the vanes are gummed up, surely performance would be rubbish all the time! i cant get my head around the fact that surely theyd be faulty all the time, although obviously i bow down to greater knowledge :-)

so.....any more thoughts advice would be appreciated. i accept theres a big bill coming my way, so im wondering whether its worth cutting my losses and part ex'ing on a new one at a garage? garage owner did say itd be a shame if it was kerplunked cos its a mint verion for its age, which was nice to hear, but still doesnt stop that big bill looming! :-(

thanks

thanks

I think the best bet is to remove the lower of the 2 pipes on the left hand side of the n75 unit and apply a vacuum to the it (stick it in your mouth and suck). This should cause the actuator rod on the turbo to move.

If it:

- moves smoothly then the vanes / control ring in the turbo is fine and the problem is elsewhere - vacuum, n75, etc.

- does not move at all it is badly jammed up (or you are not sucking hard enough)

- moves but is sticky/non-smooth then the vanes / control ring is partly jammed up.

If you have a thin arm you can get it down the back of the engine, between the EGR assembly and the brake fluid reservoir and feel the actuator rod. Otherwise disconnect a bit more of the hose (it is just clipped in) or extend the pipe so that you can be under the car, with the under tray removed (8-10 torx screws) and then suck on the pipe and see if the control arm moves.

When was the air filter last changed?

Garages generally quote about 3 hours labour to remove & refit a turbo. You then need a number of gaskets, and maybe a new oil supply pipe too. I removed mine at home and cleaned it over a weekend.

I think the best bet is to remove the lower of the 2 pipes on the left hand side of the n75 unit and apply a vacuum to the it (stick it in your mouth and suck). This should cause the actuator rod on the turbo to move.

If it:

- moves smoothly then the vanes / control ring in the turbo is fine and the problem is elsewhere - vacuum, n75, etc.

- does not move at all it is badly jammed up (or you are not sucking hard enough)

- moves but is sticky/non-smooth then the vanes / control ring is partly jammed up.

If you have a thin arm you can get it down the back of the engine, between the EGR assembly and the brake fluid reservoir and feel the actuator rod. Otherwise disconnect a bit more of the hose (it is just clipped in) or extend the pipe so that you can be under the car, with the under tray removed (8-10 torx screws) and then suck on the pipe and see if the control arm moves.

When was the air filter last changed?

Garages generally quote about 3 hours labour to remove & refit a turbo. You then need a number of gaskets, and maybe a new oil supply pipe too. I removed mine at home and cleaned it over a weekend.

ill ask the lads at work whether theyd be happy to try that method, i dont feel confident doing it myself. no idea what an actuator is, what it looks like, or wher eit is :-/

as for the air filter, i had one of the lads service it a month or so ago. ill check that he did that. would i be able to tell myself, and would that make a difference?

thanks a lot

If the air filter is only a month old (assuming it was changed), then that should rule that out of the equation.

TBH: If you don't feel confident about checking things yourself, you are going to have to bite the bullet and pay someone. If you tell us where in the UK you live, someone might be able to recommend a good indi who might have have a look and not charge you an arm and a leg!

If the air filter is only a month old (assuming it was changed), then that should rule that out of the equation.

TBH: If you don't feel confident about checking things yourself, you are going to have to bite the bullet and pay someone. If you tell us where in the UK you live, someone might be able to recommend a good indi who might have have a look and not charge you an arm and a leg!

would a blocked air filter give these symptoms? woud it be obvious by looking at it whether its a new one or not? btw, im in lincoln mmate.

thanks

A really dirty air filter could not help, but I doubt it would be the single cause. My car always seems to run better a few filter, but mine only get changed every 30k (long life servicing schedule). If the filter looked like a forest floor then changing it would be no bad idea...

Have you tried driving it with the MAF disconnected as per posts #2 and #5

ill check the air filter then and report back thanks.

as far as the MAF goes, i havent tried this as im scared to :-D but.... looking back at the pictures, ill maybe give it a try if i can identify it ok. is it just a case of unscrewing it and leaving a hose flapping? and how long could i drive it for before id be damaging something? a 2 minute drive round the block or a 20 mile commute, and 20 miles back home to check it?

ill give the garage a ring today too, and ask them if they actually tried that, and what their next course of action will be if i take it back in.

thanks

For the MAF sensor all you need to do is disconnect the plug on it (leave the actual sensor assembly in the air pipe, so all that flats about is a plug from the loom.

With the MAF disconnected the car will run on a default air profile. You would need to drive it long enough for the limp problem to normally occur. However if the car feels more lively immediately then that is a very good indication that the MAF is faulty. A car with a dead MAF will feel very flat, and one with a failing MAF might lack power when you need it most - on a long gentle uphill (for instance).

For the MAF sensor all you need to do is disconnect the plug on it (leave the actual sensor assembly in the air pipe, so all that flats about is a plug from the loom.

With the MAF disconnected the car will run on a default air profile. You would need to drive it long enough for the limp problem to normally occur. However if the car feels more lively immediately then that is a very good indication that the MAF is faulty. A car with a dead MAF will feel very flat, and one with a failing MAF might lack power when you need it most - on a long gentle uphill (for instance).

blimey that was quick!! :-)

disconnect a plug, is that all???? :-) even i should be able to do that! although, wouldnt you think that the garage should have done that as a matter of elimination? like i say, ill ring them and ask.

probably a daft question, but say there was a problem with the MAF (which showed up with it running fine when disconnected), what would be the implications of leaving it disconnected?

thanks

Not sure on the implications on the TDI but on the 1.8T if you run without the MAF it may be over or underfuelling a bit because it's having to assume certain air flow values, it's not a biggie but you can run around with it unplugged until you can get hold of a replacement.

Not sure on the implications on the TDI but on the 1.8T if you run without the MAF it may be over or underfuelling a bit because it's having to assume certain air flow values, it's not a biggie but you can run around with it unplugged until you can get hold of a replacement.

just rang the garage and asked about the unlugging MAF scenario. he said that that would cause it to run flat or something, and if there was a fault elsewhere, it wouldnt show it. phone line was crap tho and i couldntt really understand what he was actually saying.

just rang the garage and asked about the unlugging MAF scenario. he said that that would cause it to run flat or something, and if there was a fault elsewhere, it wouldnt show it. phone line was crap tho and i couldntt really understand what he was actually saying.

just tried taking the plug off and couldnt suss it. tried pressing down a lug with a screwdriver to try and pull it off, but it wasnt coming. i dont think ill make a mechanic will i :-D