Colin59

A few days after a 3 day PCA driving event with Northern New Jersey region I had a rumble sound and loss of power in both normal and sport mode - noticed boost wouldn't go above 0.5 bar. Then the check engine visit workshop came on.
At the dealer they found P1095, P1096, P1256 and P1373. They reset the faults and road test and found that P1096 returned.

Comments about bypass air contaminating the Mass Air Flow sensors so they replaced both mass air flow sensors and recommended that I go back to the stock airbox, to replace my Werks 1 airbox. I used the air filter assembly part.

They had also found a sticking valve lift solenoid and seized boost pressure control rods. They cleaned and lubricated these.

(They checked actual again and found the Mass air flow sensors balanced and at middle of operating range (one was high and the other at the lower end of the range) road test and no codes...air duct to be added once in.

valve lift fault may likely return (oil change done elsewhere 4000 km ago) solenoid likely sticking.

I did another 2 day track event Mosport and on my last session on the first day and again on the second day after getting the visit workshop code I noted I was down in power by reduced end of the back straight speed. I had my local mechanic friend run the codes. Details:
On my track day yesterday I had 3 runs without error codes and the car worked well with normal power ( a little less perhaps than with the carbon fibre air box) but on the last run last lap at the hottest part of the day I got a visit workshop engine code. The visit workshop notice cleared before I started the car this morning. I had his checked at the track (it was 2 x P1096 codes) this morning and then reset.
>
> Today no codes for the first two fast sessions then near the end of the third - again at the hottest part of the day I received the visit workshop error codes, I also noticed the power reduced over the next two laps until the end with my top speed reducing by about 15 kph at the end of the straight, so I skipped the final lapping session and went home. When I went out ~ 4 hours later the visit workshop alarm had cleared. When checked I found again that I again had the same 2 x P1096 codes.

My dealers response to the above was:

> It appears that the change out of mass air flow sensors and airbox didn't correct the problem.

Please Rennlist turbo experts advise??

Thanks

Colin
997TT

Kevin

Colin,

What are your mods? ECU Tune, Exhaust? Are you running race gas?

Here is the CEL print out. You need to look at your throttle-body and gasket (hose clamp also), the low lift/high lift solenoid needs to be looked at, AND I would suggest a Intake Pressure test.

P1096

Mass air flow ahead of throttle valve implausible (too high)

Diagnostic conditions

•Supply voltage 10 V ... 16 V
•Engine start
•No faults detected for throttle valve adjusting unit, ambient pressure sensor, intake temperature sensor, speed sender

NOTE: In this context, please also observe the function description.

Possible fault causes

•Hot-film mass air flow meter faulty (battered)
•DME control module faulty (ambient pressure sensor at fault detection threshold)

Mass air flow upstream of throttle valve implausible (too low)

Diagnostic conditions

•Power supply voltage 10 V ... 16 V
•Engine start
•No faults detected for throttle valve adjusting unit, ambient pressure sensor, intake temperature sensor, speed sender

NOTE: In this context, please also observe the function description.

Possible fault causes

•Air cleaner blocked
•Leakage between MAF sensor and throttle valve adjusting unit
•Throttle valve sluggish or heavily soiled
•MAF sensor faulty (battered)
•One or both cylinder banks remain jammed in small valve lift
•DME control module faulty (ambient pressure sensor at fault detection threshold)

Function description

Diagnosis of plausibility of MAF sensor signal

•The measured value supplied by the MAF sensor is compared to a value from a map. This map is determined by engine speed, throttle valve position, ambient pressure and intake air temperature.
•The mass air flow upstream of the throttle valve is identified as implausible if the measured value deviates too greatly from the map.
•If the switching cups stick on a small stroke on one or both banks (e.g., oil duct blocked), the MAF sensor can also be detected as faulty. This is because the expected increase in the air-flow rate does not occur.
•The monitoring of electrical faults (open circuit, short circuit) takes place in a separate diagnosis.

Kevin

How many track days are on your oil? I would think about changing the oil and filter. If you have a lifter being stuck you will get the 1373 codes.. Misfire codes will also come..

Colin59

My 997.1 TT has some mods installed by the first owner, including IPD intake tee, GIAC tune, did have tubi exhaust but was replaced with the stock one by the previous owner, and did have werks 1 CF intake as mentioned in the original post.

The oil was changed April 7th an I have done ~ 5000 highway commuter miles and the 5 track days mentioned.

I use Sunoco 94 pump gas which includes alcohol.

I have ~ 154000km or about 95000 miles on the car and it is a daily driver year round, including he Canadian winters.

The dealer also mentioned the possible valve lift being stuck in low lift? This does seem to align with your assessment - is it possible that they need replacement? I will try an oil change first... The dealer said at least 5 hours labour to remove everything to access the solenoids with the parts being about 300 cdn each. IF this is happening wouldn't I expect the 1373 error code each time?
To replace the lift solenoids, the spark plugs would also be accessible so I expect I would change them at the same time.

Thanks for the input any additional advice would be appreciated.

Regards

Colin Barfoot

Macster

5K miles and 5 track days on the oil is pushing the oil's service life. For my 996 Turbo with no track time I change the oil every 5K miles.

For any track time, you should show up at the track with fresh oil.

I hope in your region you are running 0w-40 oil? At least in the winter.

Kevin posted some good info regarding the possible causes of the errors.

Sometimes error codes point to a relative simply thing to address, like say an O2 sensor.

Other times, not often, but I think this is one of those times, a more in-depth investigatiion is going to be required.

For instance a bank of lifters (or just some lifters) being stuck in low lift (or high lift) mode can require more focused testing to confirm.

You can try an oil/filter change but the oil would have to be pretty bad for fresh oil to make a difference.

Colin59

As noted I will get the oil change done once my local Response Engineering shop is available and see if that does make a difference, I have another 2 track days Sept 25/26 to evaluate. I would prefer to know prior to the track day if you can suggest any specific diagnosis we can do - other than changing out the solenoid valves of course.

I do run 0w40 in the winter. Synthetic always, intially Mobil 1 then Motul and lastly a Liquid Moly.

Regards

Colin

Macster

The factory manual for the 996 Turbo offers a pretty detailed test for problems with the low/high lift mechanism not functioning properly which in the case of the 996 Turbo can result in persistent misfires.

I don't have the 997 Turbo factory manual but I suspect it also has a section detailing the steps to take to diagnose a problem with the VarioCam Plus and its low/high lift system.

From my memory of the 996 Turbo diagnosis it involves road testing the car while monitoring individual cylinder misfires counts along with O2 sensor readings along with observing when low lift or high lift is active.

The problem can be at the bank level -- the hydraulic valve that engages/disengages the low lift feature is not working properly -- or at the cylinder level as one (or more) intake valve lifter and its low lift locking pin is stuck and non operational.

I'm not sure I'd engage in any more track time until I got this resolved.