996 missfire & no power

[albin]

I have a 996 3.4l (1999) tiptronic with 140'000km. The engine was rebuild at 80'000km and the tiptronic rebuild at 100'000km.

I face a strange problem since many month. I try to explain symptom in chronological order.

- When it rain during the night, I need to start two time the car. The car start alway from the first power on, but no power at all. I need just to power off and re power on and the car work fine.

- One month after, the car is running on 4-5 cylinder after the second power on... lot of missfire.

- The garagist change all 6 spark, 6 coil, the AOS (leak problem), the MAF and the two lamda probe...

Now the car run almost good except: ans this is my question. Could you help?

When i drive slowly (following car) between 1'500 and 2'000 rpm (rpm important) in 3 or 4 gear (tiptronic) and I would like to speed up to overtake a car, the engine do not ramp up rpm, lot of missfire, the gear do not swith to 2 quickly and accelerate...!

When i accelerate from 3'000 to 6'000 no problem the car run very well.

Now, the garage tell me it is a tiptronic problem...?

Could you help me on the road to find a solution ?

Thanks in advance

[Loren]

Best get the fault codes and find out what the DME is reporting for the faults.

It is just guessing without the fault codes - so post them here and we will help.

Exact model and year of your car would also help.

[logray]

+1 to above post, without codes it is just a guessing game.

That being said however... your RPM ranges and problem description might indicate there is a problem with the variocam system... but I wouldn't be surprised if it is related to the transmission as well.

[albin]

Hello all, thank you for your answer.

I Forget to give you an important fact. No error code on Durametric....

(before we cahnge the lambda we receive a lamda error code)

[logray]

If you truly have misfires and those unexplainable symptoms without any codes and can verify this with another scan tool, I would highly suspect your DME and/or tiptronic computer.

I have seen a faulty DME with a bad flash randomly cut out while running and do other strange things before and not throw codes.

That being said, I would double check there are really no codes using another scan tool before replacing the DME.

Also, your symptoms do sound like a possible variocam issue based on this "1'500 and 2'000 rpm (rpm important)", since this is around the range variocam advances valve timing.

That being said, you could be facing multiple problems.

[albin]

Thank you a lot for your informations Iogray..:-)

I just have one more symptom from last weekend. I drive on a highway sloping up without moving the accelerator pedal (fix). When the engine is about 2'000 rpm... no way to stabilize it.

It alway pump himself between 1'800 and 2'000 rpm at a frequency of 1 by second.

It can help you ?

Anyway I go to anhoter garage to make new reading error code with new reader

[logray]

Really difficult to say from your description and no codes, but it could be any of the things I already mentioned.

It could also be the rpm signal is being lost (crank position sensor), gears slipping, torque converter slipping, or something else or a combination of these issues.

[RFM]

Have you already cleaned the idle control valve and throttle body, and tried another brand of 98 RON fuel? It can help to solve the unstable engine RPM between 1.800 and 2.000.

[albin]

Hi guy,

I would like to give you the solution. Now my 996 run as brand new one..:-)

The Porsche Center of Geneva simply make:

- clean the throttle body

- RE program the Tiptronic control unit, not only reset it.

- change the tiptronic gear oil

I am happy