Help help .. Limp mode is driving me insane !

**Diwestiny** · 16-06-2012,02:56 PM

I need some help as I feel like committing suicide .....
My '99 A3 1.9 Tdi Sport, with 183k is doing my head in ! Whilst merrily driving along the dual carriageway then going to accelarate under load (like uphill) the limp mode kicks in and lost of power .. so no overtaking ! This happens everyday on the way and return to work. In less than 5 miles from departure point. However, if I stop at traffic lights and turn the ignition off momentarily the ability to overtake returns for a brief period. The Audi dealership said turbo is losing gas and needs a new turbo, but I am not yet convinced because it works ok until the limp mode kicks in and also after I turn it off and restart it is fine. There is no smoke or noise coming from the turbo. This started as a intermittent thing, which is now regular as clockwork. However, I visited a friend who had a look at a couple of things under the bonnet, intake hose and a value behind it, also looked at the air filter, took it out gave it a tap (it is in pretty good condition) and put it back. He suggested I looked at the inlet hose when it happened with the engine still running to see if the hose collapsed. I went on my way put some diesel in and put my foot down waiting for the inevitable .. no limp mode ! I had a good drive round about 15 miles still no limp mode ! Unfortunately my joy did not last and the next day going to work the same thing happened but I remembered to look at the hose before turning off, and to my disappointment it was ok. My next course of action was a diesel place. Here they did a diagnostic and told me it was the wastegate had stuck so they did an adjustment, but unfortunately that did not work either. I have since changed the fuel filter too, and no difference there either. A friend with one of those electrical meters had a look at the Air Mass Sensor, the connectors were clean and the his tests showed the right currents or whatever were good. When it happens I can rev it and the revs will go up with no problem, it just happens under load ... it is also pretty embarrassing too !!!! So can anyone help or recommend somewhere in Sussex I can go to ???
Bytheway I get no codes or lights appear on my dash either !

**zollaf** · 16-06-2012,05:10 PM

welcome to the forum. first thing to establish is exactly which engine you have, as there are several it could be and the fault could be different. so, look firstly on the timing belt cover, or failing that the label in the boot under the carpet, or in the service book, with loads of numbers and letters on it. one will be 'engine', and will be 3 letters, such as awx, arl, ahn, etc, .
see what you can find and let us know.

**Diwestiny** · 16-06-2012,06:02 PM

Originally Posted by zollaf

welcome to the forum. first thing to establish is exactly which engine you have, as there are several it could be and the fault could be different. so, look firstly on the timing belt cover, or failing that the label in the boot under the carpet, or in the service book, with loads of numbers and letters on it. one will be 'engine', and will be 3 letters, such as awx, arl, ahn, etc, .
see what you can find and let us know.

Ooops I forgot to mention that, sorry. The engine code AHF.

**zollaf** · 16-06-2012,06:19 PM

ok, i wonder if it is overboosting, so cutting the fuel off. my money would be the same as i have just had on my 1z engine, and that was the n75 wastegate valve. electrically it was fine, but siezed up inside so not opening the wastegate. the ecu see's more boost than it wants, so shuts the fuel down, hence limp mode. from the wastegate there is a thin rubber pipe going to a little valve, the n75. firstly make sure these pipes are in good condition as if one leaks, that will cause it. if they are good, then apply 12 to the valve. its marked + and -. if it clicks then its probably ok. it diverts air from the boost hose into the wastgate, so you can remove it and check its doing what it should.
this is presuming its the same set up as mine is, which i am pretty certain it is, and it is a common failure.

**Diwestiny** · 16-06-2012,06:44 PM

Originally Posted by zollaf

ok, i wonder if it is overboosting, so cutting the fuel off. my money would be the same as i have just had on my 1z engine, and that was the n75 wastegate valve. electrically it was fine, but siezed up inside so not opening the wastegate. the ecu see's more boost than it wants, so shuts the fuel down, hence limp mode. from the wastegate there is a thin rubber pipe going to a little valve, the n75. firstly make sure these pipes are in good condition as if one leaks, that will cause it. if they are good, then apply 12 to the valve. its marked + and -. if it clicks then its probably ok. it diverts air from the boost hose into the wastgate, so you can remove it and check its doing what it should.
this is presuming its the same set up as mine is, which i am pretty certain it is, and it is a common failure.

Thank you for that I shall get that investigated on Monday hopefully. Now if it isn't (I have to ask this being a woman ! lol), what then ?

**zollaf** · 16-06-2012,07:11 PM

to be honest, there isn't really a lot else it can be. i am suprised there are no codes though. in fact, there must be a code for it to go into limp home. did vw not find a code ? a cheap generic reader is no good, as that will only find obd codes. you need a proper one, like vcds or a bosch kts or snap on modis. if you look in the vcds section, there might be someone local that you could liase with to get them read.

**Diwestiny** · 16-06-2012,08:06 PM

When they looked at it they more or less wrote it off, as I did not stand and watch on this occasion I have doubts as to whether they actually did anything other than a quick look, old car it needs this, this and this and it will be expensive, etc. The place I went to that does auto and marine did not get the codes you are talking about, but that is due to not having the full diagnostic equipment for my type of fault. However, they did mention some other Bosch equipment but they did not decoder references (if you know what I mean) for the codes. Well at least I have a couple of days to work out who I shall call on ... poor souls !!!

Thank you for that, I like to know my options no matter what they are.

**machinedred** · 18-07-2012,09:55 AM

I have this problem too!? Did you find the cure?

**Diwestiny** · 18-07-2012,04:36 PM

Originally Posted by zollaf

to be honest, there isn't really a lot else it can be. i am suprised there are no codes though. in fact, there must be a code for it to go into limp home. did vw not find a code ? a cheap generic reader is no good, as that will only find obd codes. you need a proper one, like vcds or a bosch kts or snap on modis. if you look in the vcds section, there might be someone local that you could liase with to get them read.

Well a couple of weeks ago I went to garage who had the right facilties to do the diagnostic and the out come was as you said overboosting and after a more thorough investigation it appears the variable vanes are not working as they should be, pipes were all good, so you can guess what I need. Yes its a replacement turbo ... deep joy !
Thank you for your help, much appreciated.