Our 996 refuses to run over 4500RPM!!!

Strange thing: our 996 refuses to accelerate over 4500-5000RPM! It is running well under this limit; good acceleration... But it begins toi jerk horribly when it reaches 4500RPM and refuses to pass over! It's equiped with a tiptronic gearbox. Changing gear is not a problem and works perfectly, in manual or automatic mode. Any idea?? Thanks!

Most likely the crankshaft position sensor. Thats a common symptom of what you're experiencing You Tube

Yep, this could be the cause... Will try to change it! Thanks a lot for your reply!

Probably not the issue but check to make sure there is good flow out of the exhaust. U should be able to detact it with just a glove on over the exhaust pipe to see if u had a cat come apart and restrict flow.

Split fuel line in the fuel tank. It will keep getting worse. Take out the fuel pump and inspect all the hoses. The "U" shaped rubber hose is probably split. Replace it with submersible fuel hose (not ordinary fuel hose!).

I can't imagine an issue with fuel line. Why? because I did tests at full charge under 4500RPM and accelerations are proper up to 4500RPM. If I'm trying to pass over 4500RPM slowly; that remains the same: engine is immediately jerking horribly, Rev counter is sweeping from 2000 to 4500!!! I'm mostly looking in direction of an electrical/electronical issue! Maybe a DME failure, or something similar. Understand me, if you stay under 4500, the car is going very well, even if you accelrate strongly or lightly. I'll also explore another way, by servicing the tiptronic... Will let you know... Cheers,

Dont discount the fuel line. Its an easy check..... Its a matter of volume and pressure. A split in tank line will cause the issues u r having. Will the engjne rev over 4500 when in park or neutral (no load)?

Keep in mind along with these other possibilities that the DME may have somehow got back into "transport mode" .. In Transport mode the RPM's are limited along with other non-essential functions that are not necessary when transporting across the Ocean for months.. Performing a "Handover" with a PIWIS Tester will take the system out of Transport Mode.....I have seen a few cars that had gotten back into Transport Mode somehow due to some strange voltage/electrical issues.. It's worth a mention !!!

Thanks for this! I have a PIWIS 2 and an original 3. Have you a procedure to do such operation? FYI: I've already changed the crankshaft position sensor, without any effect...

Quotes source post: 20009594

Just get to the 996 main menu , then look across the bottom for "additional menu", then select " Handover" and follow the prompts ....... If this doesn't fix it then put a fuel pressure gauge on the fuel rail and test the pressure at full throttle up to where it cuts off...Fuel delivery is the number 1 cause of full power issues...

Thanks for the process. I did it and wait for the result from the owner... In the meantime, I servised the tiptronic and noticed problem with tiptro switch connector!! Piwis indicated wrong tiptro position !!! I sprayed some contact cleaner and all come back to normal on this point. Better than nothing!!

To complete the topic, spark plugs and coils were already changed!

Just a crazy thought but I would assume you looked at the air filter? Any issues with restriction?

With air restriction I couldn't accelerate "foot in" at low rev! Here the car is running perfectly with "heavy acceleration" up to 4500RPM! Then, I'm doubful about any air restriction due to dirt air filter. But, thanks for your suggestion.

Boy then it has to be on the fueling side. Does it struggle after 4500 or just dies off? If it's struggling, it's fuel pump or fuel filter related. It wouldn't be dirty injectors if it's pulling hard to 4500....so my thought is it would have to be the fuel pump or filter? Hummmmmmmmmm

Yep, another way to explore... Except DME failure, all the rest was changed: Air flow sensor, lambdas, spark plugs, coils, crankcase position sensor... Engine struggles when reaching 4500-5000, by shaking horribly. Rev count is sweeping between 2000 and 4500. I'll check if fuel filter is built-in the fuel pump or s�parate. At this stage, no more news from the car's owner....

Quotes source post: 20010320

How many miles are on the car? Happen to do a cam variation reading by chance? I wonder if the chain(s) pads are wore out that much if that would cause it to stumble?????

Well the car has 130.000KM! But engine was changed for a brand new one. Now engine should have 5000Km... In fact, due to run in, never the owner tried to pass over 4500 RPM!! Then, as the engine was delivered in 3 parts (crankcase and 2 cyl heads), an error made during its assy is not discarded! As this point, 2 things remain to be checked: fuel distribution from the tank to the engine, but also DME. Again, the significant thing is under 4500 the engine run absolutely well, with good accelerations, tiptro is also working well.

Can you share a video of the situation? I�m having trouble trying to imagine this scenario.

I'll contact the owner. We shot videos during test drive...

Thank you!

You're very welcome!!

Well videos are not very explicit!!! As you can see on rev counter, accelerations are correct up to 4500-4800, in both case: heavy or light acceleration ! 4800-5000 is like a barrier impossible to pass thru! 2 videos here: https://mega.nz/folder/DeQTVaBK#URgPil-ywp22GUQmxJpMYw

Thank you for the videos. I believe that there is an issue with the transmission or its control system. Have you scanned for any trouble codes in the transmission control module?

No trouble on tiptronic module! Just, during servicing the tiptronic I've noticed some bad connections into the tiptro switch connector. Tiptro lever indicator onto the PIWIS was not properly reported. Then, I've cleaned up the connector and all were come back to normal. Despite of this, the problem is still present!! More and more, I'm thinking about DME cartography corruption!!! Friend of mine will try to reload it. Will let you know...

We'll try to reload the DME the 4th of May... Will let you know...

With my friend Alex, we just wonderring if we are not facing a configuration issue!!! Major part of flat-6 have 4 Lambdas probes! Few of them have only 2! This is the case of the 996 we are working on. Maybe the DME was loaded with a "4 lambdas" mapping! Alex has already encountered such issue on boxster 986... with similar effect. We'll know more on Sunday.

Sorry for such delay... We were obliged to postpone this operation. Stay tuned! we'll come back later...

I really would like to know the outcome. Do keep us posted, please!

Show us a video of the fuel pump and hoses. That would be good.

Dears, Some additional news: O2 probes were changed; same problem. Also, in complement of this rev limitation to 4500rpm, sometime, it refuses to start, when hot. Fuel line is ok. I'm also looking to a potential problem which could come from variocam! Is there anybody who know symptoms generated by variocam issues? Thanks,

Didn't read in your posts that you've replaced the crank position sensor. Have you? The additional symptoms of no hot start is plausible due to a further degrading sensor (signal). Ideally you scope the signal as it enters the DME by sticking the probe into the back of the dme connector after removing the connector housing or by viewing it on piwis

Quotes source post: 20009594

Was mentioned here

You may want to check the signals from the Tiptronic Moduale to the DME....and in the Tip module If the DME thinks theTip is in P or N it will have a 4500 RPM limit........

That's a very good way to follow!!! DME as well as tiptro calculator haven't any error when checked by PIWIS. I'll check wiring between tiptronic and DME and will let you know... Thanks,

Dears, Sorry but no news, no feedback coming from the car's owner... As you, I'm a bit disappointed... Anyway... I've also seen another funny story: a boxster 987 owner who would like to save some money, has undone his engine from his car, to make it repared by a "professional engineer"!! I've put bracket as the engine when re-installed in the car does not run very well!! With issues described, it appears that timing chain was not properly set on a cyl bank!! Of course, the "pro" refuses any responsability for this issue!! Then, guys: on this case, 2 ways to follow: - Bring your car to the pro to do the job, from A to Z! - Do the entire job yourself, if you are able to do it FYI...

Hi there, Another step into this "never ending story": the 996 owner come back to me to change the tiptro positioning contactor. I've changed it for a brand new one, and check tiptro position with the piwis. On this side, all is OK. But problem remains the same... no possibility to pass over 4500rpm! despite of this, something new: O2 sensors bank 1 and 2 were in fault! so that means problem with mass air flow sensor! engine running, when I reset this fault, idle rev is changing significantly. Also, sometime, the engine has difficulties to start!!! but, when started, no more problem on this side. When this psoblem occurs, the car smels gas horribly !! So, I've suggest to the owner the following: - change the mass air flow sensor - change the fuel pump. - maybe to change also the cranck top dead position sensor. When done, I can't see anything else to do!! What do you think?

Dude, you have not yet Tested the fuel pressure under full throttle..... That should be the first thing you test when there is a lack of power under full throttle.... Yes it is not as easy as throwing parts at it or Guessing, but should always be the first or second thing to do ...

I�m betting split internal fuel line(s)� especially if it�s a C4 (saddle tank). I had this happen on my brand new FSI stage II build a few years ago - It even took Jake a while to figure it out (mine was topping out at about 6k though). I thank god it happened while they still had the car and found it in testing/tuning!

Quotes source post: 20044949

C4 or C2? How do the fuel lines look in the tank? Pull the sender and the pump?

C2 - 3.4L - 2001...

It sounds to me that the car may have developed a vacuum leak in addition to the 4500rpm issue. I would check the car for any vacuum leaks first, and test the air-oil separator (AOS) too.

4500-4800 rpm can be achieved but then horrible shaking as well as tach needle sweeping wildly? The latter could be an indicator that the crank signal is seriously bad. It works OK up to the revs as observed but then it's corrupted by RFI, gap between sensor head and flywheel teeth too large, wiring with intermittent loss of contact or a bad sensor itself. Get that signal hooked up to an oscilloscope at DME connector and observe.

Good idea, as well... Since last post, Fuel pump changed! Same result. As I'm not sure about how the engine was built (delivered in 3 packs (cyl heads were delivred apart), I've strongly suggest to check carefully the engine timing. This is a 5 chain timing engine.Then, a double check could be useful...

Tomorrow last change before engine deposit! I have a recurrent fault on DME for both side with O� probes. Then, this could mean an mass air flow probe problem! I'll change it tomorrow. Then, it'll be time to check timing seriously. Again, keep in mind that such engien was rebuilt and re-installed by somebody else! I'm just in front of this problem and follow owner informtion. At this stage, The only remaining thins to do I can see is timing check! all the rest which could be cause of this problem was changed already. Will keep you posted...