Hey guys,

I'm having an interesting problem. While cruising around on the highway in 6th gear under boost, the car will buck and lose boost. From then on, it will only make 6psi of boost no matter what I do.

As soon as I shut the car off, and turn it back on again it comes back to normal. It doesn't set any check engine lights or do anything to suggest that something is wrong, other than it refuses to make more than 6psi.

I'm not sure what's causing this, it's starting to get really annoying as it's happened 3-4 times now. Any ideas?

Thanks,
Dan

 

any recent mods?
suspect boost hose leaking.

 

To follow your thought, are you saying a boost leak is causing intake temps to run high, perhaps knock, and the DME is shutting down boost to protect the engine?

The car is completely stock, I haven't done any mods to it.

 

Your Y pipe or hoses are loose.

 

How do you cruise in 6th gear under boost?

 

With a 2011 911tt if you're cruising at 80mph in 6th you are right at the boost threshold, and it's really annoying. I'm sure the gearing is pretty much the same across all the 997tt's. Boost threshold may not be.

--CC

 

I deadly with this purple just recently. Would boost past 8 psi. ended up being my upper intercooler hoses had popped off. Didn't put then back on all the way when finished up my exhaust installation.

 

Check any boost hose for getting loose...and for sure check BRVs...they tend to stuck and boost stays low...also read codes and if you have "turbo underpressure" you might have melt one or two cats...

 

I suppose you're catching the back half of my dry humor, but as previously said 80-85mph is right on the boost threshold in 6th gear. As I'm driving around and speeding up/slowing down I'm hitting a good amount of boost in 6th.

Sure enough, the other clamp on the passenger side of the plenum had come loose. I took it by the dealer and had them put it back on, they went ahead and ordered a new snorkel/boost hose/whatever and said they would swap it out since it has come off twice now. On the way home it popped off again, so I got out my socket set and put it back on. I probably overtightened it, but at least it hasn't come back off. I'm not too worried about hurting it since they are going to replace it next week when the part comes in anyway.

All of that said, I still don't understand why it drops to "limp" mode at 6psi. I guess the question I'm asking is what condition is triggering that to happen? Intake air temp? Knock threshold? Even with that outer clamp loose it still makes full boost (albiet probably not good to run it that way, i.e. overspinning the turbos as well as higher intake air temps). Then it just decides enough is enough, and has to be reset before it will give me full boost again. I would have expected some sort of diagnostic code to be set when that occurs. I guess not.

 

I believe the MAF senses an incorrect AF ratio on the intake side and the ECU pulls back timing to save the engine, preventing pre detonation.

 

Well there's no A/F ratio on the intake side exactly; do you mean that the DME notices the AFR is incorrect for the amount of metered air and injected fuel? That would make sense, but would result in the car running quite rich -- not necessarily a dangerous condition.

Anyway, it's just semantics. Definitely seems like the DME is stepping in and saying something is wrong, for whatever reason.

 

i was on the highway in sport mode, stepped on it, heard a "pop" and since then have very little boost, 6psi on highway, 9 in low gears, making a hissing sound
the Y pipe clamp looked loose, but didnt solve my problem...i am assuming it is an intercooler hose i cant get too...will bring the car in tuesday to get it fixed

surprising, no CEL or warning lights, just a lame car

 

Sounds like you've definitely got a boost hose that has come off. I've had a little more experience with this since posting in this thread. That's exactly what mine did, although I ended up having to have the Y rubber pipe replaced as it would not stay on unless severely over tightened.

6 pounds of boost just isn't that much fun .

 

Had a very similar issue.

Turns out that with a lose hose, the turbos had to work that much harder to keep boost up until eventually turbos overheated and the car went into limp mode.

Also, it gave a turbo overboost condition a couple of times until we identified the leak and fixed it.

 

please guys this is urgent i have exactly the same problem and porsche service centre didn't know how to fix it , i'm sick of this please help me if there's any thing i can do and btw i replaced the y pipe rubber and it keep loosing but the major problem is the limo mode that we couldnt find the cause of it .....