The old limp home mode again

[davered]

Hi can anybody help with my limp home mode problem leon tdi 110 se y reg 2001 84000 miles I’ve been trying to sort this out for 12 month now been looked at by various mechanics . up to now I’ve had a new turbo fitted a new maf + map new n75 valve going back in tomorrow to local vw specialist for further investigation they fitted the turbo and maf it worked ok for about 6 weeks after the new turbo was fitted then back to square one

 

[sssstew]

we would need to know some idea of why its happening which the ECU will log, get VAG COM on it and scan for the code and let us know what it is.

 

[davered]

Hi error charge pressure control positive deviation, had car serviced about 4 months ago he found some air leaks on the intercooler side after fixing car blew a load of crap out and run great for a week I couldn’t believe it, it was like a new car a lot more power and acceleration then going up dual carriage way its one big long incline it went again so took it to jvw of haydock St helens he said it’s the turbo had it done new turbo from vw £998 2 year warranty on turbo that was on the 4 of July now it’s back to square one just dropped it off it doesn’t sound very promising he had a load of cars in to work on

 

[Robb1990]

Hey mate, where you from? JVW is about 100 yards from me lol. Ive got the same problem on mine, brings the same code up on the code reader. TBH though i dont think mine is as bad, just 4th and 5th gear accelerating under load aver 2K. I just wind it up slowly. Would like to know what it is though! Ive been down to JVW aswell and they've said the same thing, new turbo, £900. Have you tried just cleaning the VNT mechanism?

 

[Robb1990]

Just been out with my code reader.

It shows on screen:

17965 - 163

Charge pressure control positive deviation

P1557
__________________________________

Hope it helps? Am i right in thinking that 17965 is the actual code?

 

[davered]

Hi got the car back he changed the map sensor and put my old maf back on I got the maf of eBay £24 cheap copy, if your car is the same as mine the map sensors under the washer bottle on the intercooler pipe work , I’d changed mine but got it of the internet used. I’ve had it up and down the link road big long incline but juddering on light acceleration so went home and put my original maf back on the one that was on the car when I bought it 12 months ago no more juddering back up the link road all seems ok not going in to limp mode and no loss of power I don’t want to think that I’ve had a new turbo fitted for nothing he told me to test it for a week ,If you’re going to change any parts get original vw parts I’ve learnt my lesson and am keeping my fingers crossed it’s the end of my problems

 

[Robb1990]

So basicly you've replace the turbo and its instant cure? id do it, but its alot of money i cant really afford, im at college atm doing mechanics so ill run it in some time and get the downpipe off and give the VNT a working/clean. looks a little awkward and there's a heat shield that'll have to come off over the driveshaft/inner O/S but should be too bad, only 3 bolts.

Ive read on the ross-tech wiki that it can be caused by loose/leaking boost pipes, but tbh i dont think mine are, when in 3rd under normal load, boot it and ill get a kick from the turbo, its not whistling away and doing nowt.

Doubt its a sensor though, it'd show up as a low value on a code reader surely?

 

[sssstew]

theres loads about this in the TDI section with people sorting it out. Rob, yes strip it down and clean it up, or get the innotec turbo clean kit which some people have used.

 

[davered]

Got my car 12 months ago never had any dealings with diesels or turbos before last car was a 2.8 merc c class before that Mazda mx3 1.8 v6 se, bmw 2.8 3 series, bmw 5 series 2.5 none of them new all under 4 grand, so didn’t know what to expect with a Leon 110 tdi only just getting use to not having all that power had to start being realistic road tax ,insurance ,mpg, you don’t get much trouble with big engine cars my experience is 9 out of 10 used cars that are for sale are being sold because something is wrong with them or something major needs doing on a service, some timing belts cost a fortune to get changed some people get rid for that reason alone what I’m getting at you may be trying to sort one problem out with a car but there may be half a dozen

 

[davered]

Worked ok for one day with new map on going to work this morning 5.30 am up the link rd did it again coming of work started car pulled of car park flat no power no turbo whistle this is from pulling away didn’t get chance to accelerate pulled over ignition of started car again can hear turbo now and it’s done this before, so 3 different maf sensors tried 3 map sensors tried new turbo fitted all pipe work and hoses checked I think I’m going to be one of the 9 out of 10 if nobody can help

 

[stevegti6]

seen that code a few times at my garage and turned out to be n75 valve

 

[davered]

Changed the n75 valve about 7 months ago didn’t make any difference

 

[Robb1990]

Any way of testing the N75? And if it had failed, would i not be getting poor running elsewhere in the rev-range/at idle? I am right in thinking the N75 controls the vacuum yes? No potentially under load, it'll fail, rather than failing totally.

 

[sssstew]

to test it swap it with the EGR valve on the back firewall, they are both exactly the same. thats how i identified my faulty valve.

 

[Robb1990]

what do you mean swap it? swap the vac feed to it?

 

[sssstew]

you will see them both next to each other, so swap them totally, so vac pipes and connector

 

[Robb1990]

nice one, ill have a look now

 

[Robb1990]

swapped em and now im still getting the pressure deviation code, but now it goes into limp further up the revs at 2900rpm rather than 2200rpm. I have been revvin it a bit harder over the last couple of days, so that may of helped.

Any thoughts?

 

[Muttley]

Sticking EGR valve and clogged inlet manifold.

Crankcase breather vapour (oily, fed into the inlet system just downstream of the MAF) combines with exhaust gas (hot, sooty) to gradually cake the inlet system downstream of the EGR with a sticky coating that builds up. This on its own restricts the inlet manifold and makes for higher inlet pressures as the system tries to deliver the correct mass of air through a smaller set of tubes. The clag builds up on the EGR valve too and causes it to stick instead of shutting as revs rise. This allows exhaust pressure into the inlet at higher revs. which the ECU reads as overboost.

 

[Robb1990]

aye im getting around all them slowly starting with the cheapest/easiest, im gonna take off the EGR next and see just how caked up it is. Whats involved in taking away the crank case breather? soot alone is bad enough, never mind the oily vapour. ive had a go at cleaning the anti shudder flap and it was well stuck with a layer of crap. It'll give me something to do for a while