Failing turbo?

[mbagge01]

I have a 2003 cayenne turbo and had a sudden issues where the vehicle went into a limp mode and the code pulled from durametric which was for low turbocharger boost. I reset the codes and now when I drive the car, it will not boost over around 10psi, which should not be the case given I have an EVOM tune on it, which will boost to around 14-15psi. I checked for codes again and nothing has come back up. It idles fine and it accelerates smoothly but with much less power. I am going to start looking for boost leaks, but if I had a boost leak that is dropping my top boost by almost 5 psi, shouldn't I be getting a code or having rough idle or abnormal acceleration issues. Could my turbos be failing? The vehicle has 78,000 miles on it.

[lewisweller]

2 hours ago, mbagge01 said:

I have a 2003 cayenne turbo and had a sudden issues where the vehicle went into a limp mode and the code pulled from durametric which was for low turbocharger boost. I reset the codes and now when I drive the car, it will not boost over around 10psi, which should not be the case given I have an EVOM tune on it, which will boost to around 14-15psi. I checked for codes again and nothing has come back up. It idles fine and it accelerates smoothly but with much less power. I am going to start looking for boost leaks, but if I had a boost leak that is dropping my top boost by almost 5 psi, shouldn't I be getting a code or having rough idle or abnormal acceleration issues. Could my turbos be failing? The vehicle has 78,000 miles on it.

Before thinking about a failed/cracked turbo..............

Check your Diverter valves. This sounds like a classic split diaphragm or vac pipe leak. 

Disconnect the DV's vacuum T piece located to the right side of the inlet Y pipe in front of the evap purge valve. Blow down each pipe they should all be closed and you should NOT be able to pass any air through them. 

 

[mbagge01]

Hey lewisweller, I had thought about that also and checked vacuum on both of my diverter valves and they hold solid without a leak. I did not find any obvious disconnection of boost hoses. My other thought was if the diverter valve solenoid could be going bad. Would this also present as a diverter valve failure and not holding the valves closed long enough.

[mbagge01]

One other thing I will add is that I just checked the resistance on my diverter valve solenoid and my N75 turbo wastegate solenoid and they both read around 26 which from what I read is a normal range. I also had an extra N75 solenoid and changed it out with no difference. I might have another N249 valve I could try to see if that makes a difference.

Edited September 19, 2016 by mbagge01

[lewisweller]

3 hours ago, mbagge01 said:

One other thing I will add is that I just checked the resistance on my diverter valve solenoid and my N75 turbo wastegate solenoid and they both read around 26 which from what I read is a normal range. I also had an extra N75 solenoid and changed it out with no difference. I might have another N249 valve I could try to see if that makes a difference.

As you have good idle and smooth acceleration I doubt any leaks, what about your maf sensors? Could try cleaning them and also the MAP sensor.

 

Can you log requested boost vs actual?  Under boost would mean its being requested by the dme tune and not delivered so check your wastegates by pressurising the pipe (10psi) which is connected to n75 valve are not leaking and opening on there own. You can hear the wastegates opening together it should and no sound of air leaking should be heard. 

 

Do you have any pending dtc? What's the condition of spark plugs and coil. Do think your getting any knock/misfire under boost and it's pulling the boost down as a result? 

 

[mbagge01]

Lewisweller, I have not recently cleaned the MAP or MAF sensors but given these items are not more than a year old, I am optimistic that they are not the problem. I could log and see what is going on. I do have am mytivac that also creates pressure and I hooked it up to the wastegate line and I could not get it to hold any pressure when I was pumping it. Should pressure build up and hold with this method or do i need to use a compressor and  try to visualize when the wategates move? 

Edited September 19, 2016 by mbagge01

[lewisweller]

21 hours ago, mbagge01 said:

Lewisweller, I have not recently cleaned the MAP or MAF sensors but given these items are not more than a year old, I am optimistic that they are not the problem. I could log and see what is going on. I do have am mytivac that also creates pressure and I hooked it up to the wastegate line and I could not get it to hold any pressure when I was pumping it. Should pressure build up and hold with this method or do i need to use a compressor and  try to visualize when the wategates move? 

The way I did it was to set the air compressor regulator to 10psi approx and the using an air gun nozzle attachment just give it a gentle burst of air pressure, you should hear the wastegates open against their spring and as soon as you release the air pressure they will creak/snap shut which is most audible. The whole test should not leak out any air from the piping or the wastegates themselves or you have a leak, any leak will reduce the boost pressure maintainable as the wastegate will be opened early inadvertly by the boost pressure on the discharge side. 

[mbagge01]

Lewisweller, how is the wastegate suppose to respond. It is suppose to hold a set level of boost with a mityvac like a diverter valve would hold vacuum with the mityvac or is an air compressor needed to create enough pressure to cause movement in the wastegate. My question is, with a mityvac, should a wastegate hold itself open with enough boost pressure built up or does the pressure just blow off when I pump the mityvac.

[lewisweller]

11 hours ago, mbagge01 said:

Lewisweller, how is the wastegate suppose to respond. It is suppose to hold a set level of boost with a mityvac like a diverter valve would hold vacuum with the mityvac or is an air compressor needed to create enough pressure to cause movement in the wastegate. My question is, with a mityvac, should a wastegate hold itself open with enough boost pressure built up or does the pressure just blow off when I pump the mityvac.

The wastegate needs pressure not vacuum to open. Bit confusing but the wastegate spring holds the wastegate shut and the boost pressure directed to the wastegate opens it. 

The way it works is the n75 valve receives a reference boost air pressure into the bottom port which is from the passenger turbo boost side, this is then directed through the n75 valve exiting the right angle port to each wastegate. With the boost pressure acting on the wastegate, at around 5-7psi it will push open against the spring holding it closed and exhaust gases will bypass the turbo compressor blades going straight out the exhaust and limit/reduce boost being built. 

When the dme wants to hold a higher boost and build to the requested boost level it will signal the n75 valve to open rapidly to bleed off the boost pressure that is going to the waste gate thus stopping it from opening and holding the boost building and or maintained. 

 

Pulse width modulation is used to cycle the n75 valve rapidly so the dme can accurately control the boost in terms of how it builds and how high it can go. 

[mbagge01]

So I went ahead and changed out the MAP sensor and diverter solenoid since I had extra ones and did not fix the boost issue. I also connected an air compressor to the wastegate line and at about 15 psi could hear clearly both wastegates opening. One other thing I will add that happened around the same time as the boost issues, I started noticing some coolant dripping somewhere from the front of the engine area onto the floor below, which I would notice when the car is parked. I have had my coolant pipes changed out but I am wondering if I might have a leak around the water pump. Is there any chance that a leak associated with the coolant system could in anyway effect building boost.

[lewisweller]

8 hours ago, mbagge01 said:

So I went ahead and changed out the MAP sensor and diverter solenoid since I had extra ones and did not fix the boost issue. I also connected an air compressor to the wastegate line and at about 15 psi could hear clearly both wastegates opening. One other thing I will add that happened around the same time as the boost issues, I started noticing some coolant dripping somewhere from the front of the engine area onto the floor below, which I would notice when the car is parked. I have had my coolant pipes changed out but I am wondering if I might have a leak around the water pump. Is there any chance that a leak associated with the coolant system could in anyway effect building boost.

Short answer is highly unlikely. I would whip out the intake Y pipe and have a good look at the water pump and the pipes lower down which run to the alternator and some metal pipes connecting the cooling to the rear of the engine etc. 

 

For me pull the plugs and check each one, (post pictures of each one, labelled for each cylinder) and a compression test wouldn't hurt. If the dme sees any knock misfires etc it could be backing off the boost to protect the engine. Boost actual vs requested Logged will tell the story better! 

 

Lastly and not to offend, your air filters aren't blocked are they? 

 

[mbagge01]

I run evom intakes, and ipd plenum. I have an inspection camera I will use to look around for the leak. Since I have a 5 psi boost drop, wouldn't that suggest a large pipe that is leaking? If I was getting such a knock to drop so much boost, should there not be a code that would come up.

[lewisweller]

2 hours ago, mbagge01 said:

I run evom intakes, and ipd plenum. I have an inspection camera I will use to look around for the leak. Since I have a 5 psi boost drop, wouldn't that suggest a large pipe that is leaking? If I was getting such a knock to drop so much boost, should there not be a code that would come up.

In my experience you would hear a boost leak unless your like my wife and can't hear anything going wrong with a car lol. 

 

What is is your maf reading at idle should be 6-7g/s and also at 3000rpm should be around 25-26g/s. Also try measuring the voltage at the back of the electrical connector of the maf. Still connected when ignition is on and engine is NOT running. You are looking for exactly 1.1 volts, (note other voltages are there too ie the supply voltage and air temp senor voltage which is built into the Bosch  maf). Any other voltage except 1.1 volts  signals a bad maf sensor according to Porsche tech instructions. 

 

 

[mbagge01]

I finally brought the car to my local Indy and they found that the leaking coolant I found was coming from the water pump. They also separated the wastegate lines from the N75 and said testing the wastegates, they function normally but they noticed that the wastegate lines When checked independently, were not holding pressure so possible the problem. When they get replaced, hopefully that will fix the problem.

[lewisweller]

On 28 September 2016 at 7:13 AM, mbagge01 said:

I finally brought the car to my local Indy and they found that the leaking coolant I found was coming from the water pump. They also separated the wastegate lines from the N75 and said testing the wastegates, they function normally but they noticed that the wastegate lines When checked independently, were not holding pressure so possible the problem. When they get replaced, hopefully that will fix the problem.

I wouldnt hold your breath that is going to be the problem. From my understanding them pipes leaking would give an overboost code and limp home mode, seeing as you have neither and seem to be losing boost. 

[mbagge01]

So they ended up replacing that wastegate line and they said that initially the car was starting hold a bit higher boost but then it dropped again and after they did some more pressure testing, they found problems with the pressure line from the turbo to the N75 valve. They are going to replace it, noting that it was very brittle and cracking. I hope that it will fix the problem.

[lewisweller]

10 hours ago, mbagge01 said:

So they ended up replacing that wastegate line and they said that initially the car was starting hold a bit higher boost but then it dropped again and after they did some more pressure testing, they found problems with the pressure line from the turbo to the N75 valve. They are going to replace it, noting that it was very brittle and cracking. I hope that it will fix the problem.

Hope they get it sorted mate but honestly I think they are barking up the wrong tree hence the story about it was "better initially". I would be looking at pulling both dv out and testing them also check the intake Y pipe for splitting under boost and intercooler piping oring leaks and the change over valve piping leaks which will limit boost and also give a bit of jerky lift off. 

Maybe something with the tune??

[mbagge01]

So I just got the car back and everything is finally fixed. It ended up that the wastegate line from the turbos to the N75 valve, pressure line from turbo to N75 valve and the line from the diverter valve solenoid to the diverter valves had a tear in the rubber portion of it when they pressure and smoked tested the system . With all of them fixed, now to the car runs well and pulls strong. When I inspected the car before, I missed the rubber tear in the line to the diverter solenoid because if you do not bend the hose in a specific manner it was not obvious to see and it must have been coming open under pressure.

[lewisweller]

1 hour ago, mbagge01 said:

So I just got the car back and everything is finally fixed. It ended up that the wastegate line from the turbos to the N75 valve, pressure line from turbo to N75 valve and the line from the diverter valve solenoid to the diverter valves had a tear in the rubber portion of it when they pressure and smoked tested the system . With all of them fixed, now to the car runs well and pulls strong. When I inspected the car before, I missed the rubber tear in the line to the diverter solenoid because if you do not bend the hose in a specific manner it was not obvious to see and it must have been coming open under pressure.

Remember my picture in previous reply showing the T peice, if you had blown hard in that you would have found the issue yourself. Regardless Good fix mate glad they got to the bottom of it. Not to be critical but except the split in the rubber bit of pipe of diverter solenoid(change over valve solenoid porsche calls it) the other pipes probably had nothing wrong with them related to this low boost issue but as sometimes is necessary to find a fault you got to try a few things often at someone's expense lol. I thrown some dollar at my pig which has left me with some "working spares" shall we call them. Lol

 

Function wise if anyone is interested:-

The change over valve changes between vacuum and boost pressure as required to hold the dv closed with boost pressure and open the dv with vacuum when you lift off. 

The dv spring alone is only able to hold against around 8psi boost so the change over valve uses its reference boost pressure from the manifold to push against the dv diaphragm holding it closed. When you lift off the change over valve switches from boost to vacuum and quickly opens the dv by pass line back to the turbo inlet to prevent the turbo stalling and the car jerking around. 

I had a melted pipe that runs from the change over valve along the injectors of driver side bank to the front of the engine and T's off to each diverter valve. I had 0.4-0.6 bar boost and really jerky on and off throttle. After replacing the pipe and both dv I get over 0.8bar holding firm and lift off is smooth. 

 

At least with your new bits and bob's you should be good to go for a while. Happy motoring. 

 

[ekstroemtj]

Fighting with the same story.

Sorry to ask guys, what is the diverter valve solenoid? Where is it?  This is the N75?

[mbagge01]

The diverter valve solenoid is the N249 valve and is situated towards the back of the engine on the drivers side hidden underneath the rear engine cover. It controls how the diverter valves open to help control boost during acceleration and also to blow off backpressure away from the turbos between shifts. The N75 valve is the solenoid valve at the front of the engine underneath the silver engine cover that says cayenne on it. The N75 is what controls your turbocharger boost levels through the help of opening or closing the turbo wastegates . Ekstroemtj, through experience of tracking down boost issues, if it is not your coils or spark plugs, it is highly likely a leak in one of the boost or vacuum lines. The solenoid valves can but do not commonly fail.

[lewisweller]

I'm working on a theory and it is just a theory that my stutter under acceleration up to 4k rpm is my wastegate(s) flap either flapping around when it shouldn't be or being wrongly controlled during boost building. I dread the idea that this problem is the turbo itself having some mechanical problem and I really have gone through everything I can to try and hunt this issue down. 

 

So has anyone got any glue what could cause perfect idle and cruising running (fuel trims perfect, no codes, spark plugs read and look good, new coils) with great power delivery from 4k rpm up to redline but getting to 4k rpm is somewhat hesitant and kangaroo juttering?? 

[JFP in PA]

Incorrectly functioning diverted valve or wastegate is the common places to start.  Turbos rarely fail, and when they do it is often a catastrophic failure (bearings).

[mbagge01]

I agree with JFP. Check all those vacuum lines at the back of the intake manifold. Also the one line I found snapped that caused similar symptoms lewisweller is the T-connector at the very back of the engine hidden down by the firewall that connects exhaust lines from the turbos and runs to the front of the engine and connects to the crankcase ventilation. It is a very common piece that can break and be overlooked when tracking down leaks.

[lewisweller]

2 hours ago, mbagge01 said:

I agree with JFP. Check all those vacuum lines at the back of the intake manifold. Also the one line I found snapped that caused similar symptoms lewisweller is the T-connector at the very back of the engine hidden down by the firewall that connects exhaust lines from the turbos and runs to the front of the engine and connects to the crankcase ventilation. It is a very common piece that can break and be overlooked when tracking down leaks.

All the pipes in the first pic below are either new or double checked. 

That T and its piping which runs forward to each valve cover is new 6months ago but when I had the manifold off a few weeks back I found it had oil and dirt around it where the metal pipes connect either side. Pic 2.  I thought bingo it's leaking but not only was it tight as f*** to remove which I didn't get it apart, I tried to suck and blow to check for leaks and it was closed both ways which is strange. Oil and dirt but not leaking? Maybe it was dirt from before and the lazy buggers just refitted the new pipe without cleaning the grim off?

Pipe 20 and 18 down to 7 and 6 what are these for?  

Pic 3 part no' 12 connects to the turbo vent pipes which goes down to a metal block thing 6&7 under each turbo.

 

Pic 4 is the actual pipe in situ as I found it. Pic 5 is the actual metal pipe into that block thing. 

 

 

 

Edited October 14, 2016 by lewisweller
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