Golf 140 Tdi power loss problems

[willyb]

Hello need some help please.

Lost power and throttle response and emissions light came on -no funny sounds or overheating.

Garage said diagnostics indicate turbo boost switch and this was replaced. Car was fine for about a week then problem reoccurred. Garage said same fault code appearing but could also be MAF. Cleared boost switch fault and suggested that I use the car (admitted switch itself although new could be faulty).
Garage have been fine and MAF would be under warranty but how can I get this paid for if it is not showing on the diagnostics as a fault?

Any thoughts welcome

willyb

[martin1810]

You need to ask the garage what the fault code number was. It sounds like they replaced the MAP sensor. If you post the fault code on here someone can probably help you.

[phil miller]

could be a split vac hose cos that will show up a turbo over boost fault code and put the car in to limp mode

[martin1810]

could be a split vac hose cos that will show up a turbo over boost fault code and put the car in to limp mode

Split vacuum hose causes underboost. ;)

[phil miller]

Split vacuum hose causes underboost. ;)

actually it brings up the fault code of boost pressure exceeded, and when reading the live data the boost pressure should be 2200ish at full boost (twice atmospheric pressure) a split vac hose means it will boost to about 2500, these are variable vain turbos its vac that maintains boost so a split vac hose WILL make it OVERBOOST, ive seen this on more mk4 and 5 tdi's than i care to remember, tbh ive never had a boost pressure sensor go down its normaly the turbo or a split vac hose, an airflow meter fault will not bring up a turbo fault code

[martin1810]

Thanks... I thought a split vacuum hose meant you didn't get any boost. Learn something new every day.

[willyb]

Many thanks for your informed thoughts and comments. Be nice if it was a split hose but latest I have from the garage is that there is "oil round about the switch". How this could cause the problem I'm not sure but they are suggesting there could be something wrong with the turbo.

Have to say I trust the garage totally having had excellent service from them for years -just get a feeling this might be pushing their capability a bit.

Any thoughts?

Thanks

willyb

[Crasher]

We need the fault code number that is stored in the ECU now.

[phil miller]

Many thanks for your informed thoughts and comments. Be nice if it was a split hose but latest I have from the garage is that there is "oil round about the switch". How this could cause the problem I'm not sure but they are suggesting there could be something wrong with the turbo.

Have to say I trust the garage totally having had excellent service from them for years -just get a feeling this might be pushing their capability a bit.

Any thoughts?

Thanks

willyb

TBH 99% of tdi's will have a wisp of oil in and around the boost pipes, its normal, as crasher has said fault codes are the way forward bud, it could very well be the vvt carboned up, to test this use a vac pump on the actuator to see if the actuator moves ( best to do this when the engine is cold) if it moves fine its not the turbo, if it doesnt move then its carboned up

[Crasher]

I have tested many with the vac pump and they have moved fine, only for it to still be carbon build up.

[willyb]

Thanks Guys

Will contact the garage for the fault codes as suggested.

cheers

willyb

[willyb]

Hi Guys,

Got the fault code as requested-P1592.

What do you make of it?

Many thanks

willyb

[martin1810]

That suggests the MAP sensor or it's wiring are faulty. The MAP sensor measures pressure in the turbo pipes. This could be the switch that your garage have already replaced. You need to ask them if that is the case. That code usually means the MAP sensor is giving a silly reading eg. open circuit or short to earth. You could try looking at the wiring to see if you can see any sign of damage. I would ask them to clear this code and see if it comes back.

[Crasher]

18000 (P1592) Manifold Absolute Pressure (MAP) Sensor -G31- implausible signal.

If the sensor is new and the wiring is good I would do a requested and actual boost pressures log and look for spiking boost delivery. In my experience on a BKD engine that code has always been a faulty turbo.

[phil miller]

18000 (P1592) Manifold Absolute Pressure (MAP) Sensor -G31- implausible signal.

If the sensor is new and the wiring is good I would do a requested and actual boost pressures log and look for spiking boost delivery. In my experience on a BKD engine that code has always been a faulty turbo.

iirc i said this a week ago and it was dissmissed :biglaugh: atleast, its being narrowed down

[willyb]

Hi,

It was the boost pressure sensor that was replaced. Car was fine for a week or so than the fault recurred i.e. garage checked the Fault code and it was the same.

They cleared the code and suggested I run the car to see if it reappeared and again after a week or it was back.

I'll go back to them and get them to do what you suggest Crasher.

For my info how would a faulty turbo cause this series of events?

Many thanks again everyone for all your help.

Willyb

[Crasher]

iirc i said this a week ago and it was dissmissed

Not by me old boy :D

[phil miller]

Not by me old boy :D


no i know mate :beerchug:

[phil miller]

Hi,

It was the boost pressure sensor that was replaced. Car was fine for a week or so than the fault recurred i.e. garage checked the Fault code and it was the same.

They cleared the code and suggested I run the car to see if it reappeared and again after a week or it was back.

I'll go back to them and get them to do what you suggest Crasher.

For my info how would a faulty turbo cause this series of events?

Many thanks again everyone for all your help.

Willyb



you need to get them to drive the car and look at the live data, to see what its boosting at, i would have thought it will be boosting to high, hench putting the light on, its prob due to a build up of carbon in the vv turbo

[willyb]

Thanks Guys, will get the garage to do as you say.

If it's carboned up does that mean a new turbo?

willyb

[Crasher]

No, it can be stripped, cleaned and rebuilt by your garage if they know what to do or completely rebuilt by a turbo specialists for around £300 if there is no actual damage to the unit.

[phil miller]

No not always, it depends how bad it is, I'd try somewhere like A&R turbos they do them for us and there service is second to nun, if you do need to get the turbo checked and want there fone number jst pm me mate

[1nfa76]

actually it brings up the fault code of boost pressure exceeded, and when reading the live data the boost pressure should be 2200ish at full boost (twice atmospheric pressure) a split vac hose means it will boost to about 2500, these are variable vain turbos its vac that maintains boost so a split vac hose WILL make it OVERBOOST, ive seen this on more mk4 and 5 tdi's than i care to remember, tbh ive never had a boost pressure sensor go down its normaly the turbo or a split vac hose, an airflow meter fault will not bring up a turbo fault code

OH MY DAYS, I HAVE A 04 GT TDI and my car does the same bloody thing - HIGHLY HIGHLY annoying.

when put on a diagnostic it saud overboost regulation exceeded. i need to get this sorted cuz i got all the power and speed (had a remap) but it shuts down at 120 mph and drops to 60mph, with no acceleration whatsoever. i also got black smoke coming out the exhaust whenever i put my foot down. car has done 84900 miles. any ideas what the black smoke could be???

many thanks in advance

[willyb]

Hi all

Update on the original thread: garage run a live data check and seem to think it is the Air Mass meter.

Reported this to my warranty provider and they happy to proceed on that basis. Given the doubts expressed re the turbo, fingers crossed.

Will keep you posted and many thanks to Crasher and Phil Miller for all the help so far.

willy

[weiser]

did you solve your problem please? as i have same problem.

tahnks
chris

[tdci115]

Another 140 owner with similar woes. Crasher is it possible for the turbo to overboost, put it in limp mode but not bring up any warnings on the dash?

[Crasher]

Yes, overboost will NEVER EVER bring on the MIL, period so it is not only possible but actually the norm, well in fact the only way it will happen. The only time the engine MIL will come on is for an emissions related problem.

[weiser]

mine does not goes more than 50mph andd 2000rpm, and when i switch off and start again it goes fine,,, its at the mechanic now i let you know, seems these volkswagen BKD the turbo is a normal issue maybe needs a clean or the vane pipes, i keep you posted.
regards
chris

[weiser]

mechanic advice that he changed the wiring harness somewhere from the map sensor after checked all the other possible faults like turbo, hoses and sensors or vacum pipes, he told me that the thread wire was a bit corroded hope that that was the problem.

[weiser]

the car wasnt fixed with that peace of wiring harnes the mechanic installed, now i have changed the boost sensor, we see what happen.

[Teflon]

Just a bit of background for you on this symptom. I hope it is helpful..................

On getting an overboost error code, many garages will change the MAP sensor as the first choice. It is easy to do and I suspect that some multi-purpose scanners pop it up as the preferred option for a solution. But if the turbo is gummed up, it doesn't fix it. Been there, done that, bought the tee shirt.

Next on the list comes the suggestion that the MAF sensor is dodgy. There often isn't a clear error code for a failure and the MAF is a favourite back street garage solution to any engine problem. My apologies for any unintended insult to the more skilled and conscientious diagnosticians among our community.

Next comes any one of a number of things, including fuel filter, crankcase pressure sensor, turbo actuator, vac pipe leaks. All are possibilities, but the frequency of failure is much less than for a simple, good old gummed up turbo. (Except maybe vac pipe leaks, which should be easily found and fixed).

In contrast, a trip to the main dealer will generally get you a quick diagnosis of a faulty turbo, for which they will suggest a replacement and relieve you of a four figure sum for the work. A service exchange unit from a specialist or else a few hours of elbow grease on the bench are much cheaper alternatives.

As Crasher has already said, the turbo doesn't always show up with a vac test on the actuator. But if you get the garage to disconnect the actuator and waggle the little lever on the turbo, then it is as plain as the nose on your face if there is indeed a problem. It should move from end to end freely and with a satisfying clonk. Any indication of stickiness or any restriction at all tells you that the turbo needs cleaning out. Remember that it gets worse when the turbo is stinking hot, so it should feel very, very free when cold, almost as if it is worn and there is too much play.

Unfortunately, I went through 4 months of the little dance I've outlined above, while my favourite local garage tried without success to solve my Audi problem. In the end I diagnosed the turbo after finding the clues here.

[weiser]

thanks for your reply, i dont have an overboost error code but, now my independent mechanic that use to work with volkswagen, had already changed a peace of wire that comes to the boost sensor and he adviced that if its not fixed by the replace of the boost sensor now he will change the complete wire from the ecu!! he checked all the pipes and the turbo aswell,, we see what happen now as i changed the sensor yesterday,