engine management light low power

[paul08050]

hi can anyone help two probs one where is my engine management light should it be a engine symbol mk2 tdi plus every time i put my foot down its a auto i get no power have to stop turn off yhen on again no faults stored changed the maf the turbo boost sensor all the vaccum valves still same does any one think its the turbo i can hear it help please

[Mirez]

Hi Paul and welcome to our forum.

1) The engine symbol is only for the V6, the diesels use the glow-plug light either flashing or steady on.

2) The common cause of this is sticking vanes within the turbo. When you say no fault stored, is this because the EML isn't coming on or have you actually scanned the car with a fault code reader? I ask because you would normally log a fault when this happens but it won't throw the warning light. If it is sticking vanes then the turbo is still serviceable, traditionally you would clear this by giving the car a good run using all of the power band (gear changes at 4K-ish) but with an auto I'm not sure if this is possible (Chris will be your man for that) - the alternative would be to remove it and clean them up although its a time consuming job.

[paul08050]

hi thanks it was plugged into vag-com with no faults only ones where i had unplugged maf sensor etc yhe technician said the actuator was moving up and down dont know if to just go for a turbo

[Chrispb]

Hi Paul welcome to the forum

By what you have said it sounds like turbo overboost but as you have no relevant fault codes, I would suggest you record some live data using measuring blocks, start a log file using blocks 003, 010, 011 you will need to get the car up to 3000 rpm at full throttle for a long as possible.

Save the file in an excel document then post it so we can have a look.

I know this may not be possible if the car is going straight into limp mode, hopefully we will see something in the log.

Make sure the turbo actuator rod is moving it's full extent without sticking, be warned it does have a strong spring inside so you may have to improvise leverage because of the location.

[paul08050]

thanks again my mistake it was plugged into vw computer because i work for a commercial dealership as its like a sharan it did read everything apart from immobiliser funny enough its not happening as often there is also a lot of oil around the turbo area running down engine

[Mirez]

Well there is an oil feed and return from the turbo so you would want to make sure they aren't leaking for piece of mind anyway.

However a light film of oil on the block is quite normal and drops down from the EGR system, specifically the actuator vent on the bottom of the EGR valve. Its caused by a worn bushing within the EGR and the only solution is a replacement valve as its non serviceable. That said its a cosmetic inconvenience more then anything else but there will only ever be a very minute amount from here.

[paul08050]

thanks for all your help re plugged in comes up with turbo malfunction so going to get one let you know what happens

[Chrispb]

That will be interesting, what was the code that came up, I think I can quite safely say I've not seen "Turbo Malfunction" as a fault code although would stand corrected.
There are a number of things that could cause under or over boost.
Wouldn't want you changing turbo unnecessarily.

[Mirez]

Correct there is no specific DTC for turbo unless you have a digitally controlled one (no Galaxy/Sharan/Alhambra has) so the code should be related to under or over boost - as Chris says that could be a number of things other then turbo failure, and to be fair the turbo's on these are extremely reliable.

The trouble is that sticking vanes will cause a DTC's to be logged. A lot of garages/dealers are aware of the cause and even the solution but since a new turbo will also fix this they prefer to go down that route as its worth a lot more to them!!!

[paul08050]

well it did say turbo malfunction n75 but its got a new over boost sensor this is the vw diagnostic system

[Chrispb]

N75 is the valve that controls the turbo actuator and the MAP sensor (boost pressure) are two different item, you really need to get some live data to see what's going on.

[paul08050]

oh right ok if it was a actuator fault is that a new turbo needed

[Chrispb]

Yes the actuator is attached to the turbo and set by the manufacturer, you can test actuator and N75 function using vagcom in output tests (registered version)

[Mirez]

I think some of the confusion here relates to the code reader being used - I have no experience using the genuine VW tool but its ouput seems somewhat ambiguous from the descriptions. Ideally get some logs from the ECU which will show what its expecting vs what its producing.

[paul08050]

ok will do thanks again for help excellent i know where to come now for any other help thanks again for your quick response

[paul08050]

well update fitted a new turbo runs better but what a suprise did it to me again plugged in got code p1556 think its slight undrboost am i wrong changed everything now

[Chrispb]

Now you have established underboost as the fault I think your next step is to carefully check the intercooler and associated pipework for leaks.
Is there any evidence of oil leaking from the intercooler as this may be the leak

[paul08050]

thanks looking at the intercoller there is a misting of oil around the hose connections

[paul08050]

also forgot to say only does it once when cold when shes warm goes great

[paul08050]

something else also when started from cold on tickover sounds like a throaty sound as though you had no air filter in not a very good description but when warm its gone

[Mirez]

Yup p1556 is a charge pressure negative deviation (underboost). From your description it sounds like a gasket in that area - the exhaust will heat up significantly and expand slightly so if you have a poor or badly fitted gasket it can seal up with heat. Its also consistent with that code. Did you replace the gasket or reuse?

Its also worth checking all the pipework from the turbo to the metal pipe, especially the first rubber angle section as they get brittle with age and can crack when disturbed.

[paul08050]

the tech used all new gaskets it was done wrer i work at a vw dealership so i sort of watched him he is very proffesional did you understand the throaty description i mentioned not sure which pipe you mean can i see it in engine compartment or is it unerneath the only new pipe was the turbo oil feed all rest had new gaskets

[Mirez]

The pipe you can't see from any angle really!!! If you take the under shield off and look at the drivers side of the engine - follow the rubber pipe back from the inter cooler and you'll find it joins a metal pipe that's bolted to the engine, at the other end of this pipe is a 90* rubber bend which could possibly be causing you a problem.

Sounds, well description of sounds are always a pain as they are very subjective but throaty/lower pitched sounds are normally caused by less pressure, hissy/higher pitched sounds are caused by more.

Do you have inspection ramps or a high curb near you? As long as it can be done safely it would be worth getting under the car whilst its warming up and feel around for and leaking air.

[paul08050]

thanks that does make sense will have a go can you tell me why the throaty noise goes when warm

[Mirez]

Thats why I was steering more towards a gasket, quite often they leak when cold but as the metal heats up and expands the gap is reduced and sometimes even seals.

[paul08050]

is the gasket on the intercooler pipework

[paul08050]

hi mirez ive been underneath traced the pipe from the intercooler and were it fits to the the turbo two bolts one bolt is missing because the piece of the pipe were the bolt goes through is snapeed off so only one holding it on could this be the cause of my problem

[Mirez]

I wouldn't be at all surprised! The turbo's trying to force all that compressed air into the pipework and inter-cooler so if it can vent that to atmosphere instead it will! At that point its technically the highest compression area as well as you have all the pipework to and from the inter-cooler as well as the inter cooler itself!

[paul08050]

thanks will replace the pipe and keep fingers crossed also aquick question im about to try and replace glow plugs does the bar accross all of them just pull off ? and do i need a special tool to take them out 

[Mirez]

Yup, just pull it (carefully) off - its a snap head fitting.

No special tool, just a deep reach socket, remember when refitting that the threads against aluminium so A) don't over tighten and B) use fingers to start the plug off and stop if you feel any resistance, that way you'll avoid cross threading!

[paul08050]

thanks for all your help 

[paul08050]

hi thought i would update had the pipe changed and for the last week its been ok even fixed my parking sensors traced to broken wires in front and rear just read the post about the guy with a auto the same withh judder about 20mph ive got that be interesting to know what that is

[Mirez]

Excellent news, its nice when everything's working!

[paul08050]

oh dear a week after being ok i drop into limp mode again but not first thing in a morning coming home from work it does it plugged in at work they seem to think its the intercooler has anyone bought the cable vagcom on ebay i did for my laptop cause i wanted to get my aux heater  to work is it worth paying the Ã,£62 to register for the full fault codes

[Chrispb]

If your only want to check for fault codes then clear the codes you dont need to register.
You can also use measuring blocks to look at live data without altering any settings.

Registering vagcom gives it more functionality, altering settings to ECU etc and you need to know what your doing as you may do more harm than good.