Hello,

i have done a 30 minutes test drive and recorded some parameters via OBD2 today.
But i was not able to reproduce or provocate the stutter. (stutter only works when you dont want it )
The ambient temperature was between 26°C and 30°C.

I have recorded the following parameters:

Device Time
Fuel Rail Pressure
Mass Air Flow Rate
Speed (OBD)(km/h)
Air Fuel Ratio
Engine RPM
Turbo Boost & Vacuum Gauge
Ambient air temp(°C)
Accelerator PedalPosition D(%)
Intake Manifold Pressure
Intake Air Temperature

I will record the data and try to reproduce the stuttering tomorrow morning again.
If there is someone out there who has knowledge about engines please let me know if you are interested in the data.

Maybe we can find a clue to solve the problem.

Thanks

Hello,

test drive is done and the stuttering appeared at nearly every stop start situation.
I have recorded it and here are some measures from the OBD2.

Barometric pressure (from vehicle)(psi) real avg = 14.504 +/- 0.000 [14.504 ; 14.504]
Fuel Rail Pressure(psi) real avg = 9064.930 +/- 3069.482 [59.465 ; 16080.334]
Mass Air Flow Rate(g/s) real avg = 17.003 +/- 12.178 [1.380 ; 82.770]
Catalyst Temperature (Bank 1 Sensor 1)(°C) real avg = 297.676 +/- 49.440 [144.800 ; 401.700]
Speed (OBD)(km/h) integer avg = 22.070 +/- 18.714 [0.000 ; 54.000]
Transmission Temperature(Method 1)(°C) integer avg = 72.331 +/- 9.454 [49.000 ; 81.000]
Catalyst Temperature (Bank 1 Sensor 2)(°C) real avg = 287.514 +/- 56.620 [128.200 ; 356.200]
Air Fuel Ratio(Measured)(:1) real avg = 22.912 +/- 4.521 [15.207 ; 29.400]
Engine Load(%) real avg = 61.512 +/- 29.504 [0.000 ; 100.000]
Intake Air Temperature(°C) integer avg = 26.510 +/- 0.919 [25.000 ; 28.000]
Intake Manifold Pressure(psi) real avg = 16.122 +/- 2.611 [6.237 ; 30.748]
Turbo Boost & Vacuum Gauge(psi) real avg = 1.618 +/- 2.611 [-8.267 ; 16.244]
Engine RPM(rpm) real avg = 1197.434 +/- 414.912 [0.000 ; 2408.000]
Voltage (Control Module)(V) real avg = 14.209 +/- 0.229 [12.700 ; 14.420]
O2 Sensor1 wide-range Voltage real avg = 0.456 +/- 0.319 [0.000 ; 1.189]
Ambient air temp(°C) integer avg = 20.176 +/- 0.508 [19.000 ; 22.000]

I can not guarantee that the measured values are correct.
If somebody is interested in the raw data please let me know.

Environmental values:
actual barometric pressure from weather website: 1014.7hPa
actual temperature from weather website: 17.4°C
actual humidity from weather website: 95%
Driving at altitude: about 90 - 98 meters

Some facts:
the temperature was lower than yesterday
it was raining today
sucking noise from turbo when shifting today, yesterday i had no or less noise
Barometric pressure from OBD is looking weird because the value was always 14.50377369 (I dont know if it is a read error)

I will do the test drive and compare the measures again this afternoon.

done the test again. same weather same problem.
Stuttering occured at least every stop start situation and sometimes between 2-3 gear.

Does anybody know if the PID33 (Barometric Pressure) is static value?
Is if also possible that the software does not read the value correct because i have always the same value 14.50377369

It's normal. It's the atmospheric pressure. We all live and breathe in air at around 1 atm = 14.5 psi at sea level.
But it seems that you have a granny style driving.
Try to test again and change gears at around and over 2100-2300 RPM.
See if it happens again.

LE: I see now you have an automatic... I was confused about the stop/start expression, a feature of manual cars.
In this case try to drive in sport.

LE2: Is this stuttering during gears, or it appears when your automatic is changing gears?

Hi Alex,

thank you for the explanation

the test drive was inner city, thats the reason for the low RPM´s.
But yesterday i wasn´t even able to provocate it with the same driving style like today.
I tried it with more and less hard acceleration.

One hour ago i tried it again, even when i drive harder i can feel the stuttering when changing gears (auto gearbox)

The only difference between today and yesterday is the weather.
How much can the air humidity affect the engine management?

Humidity today: 93 %
Humidity yesterday: 44 %

Sorry for my little knowledge about engines but i dont want to solve the problem by replacing components on suspicion.

When changing gears, an autobox, can leave the feeling of momentary lack of torque.
Now it's important how much lack of torque and how long...
I too have these symptoms, sometimes, when changing 1-2 and 2-3, but only for a fraction of a second.
How many kms has your car? Did you changed the oil in the autobox until now?

Hi Alex,

with stop/start i meant stop at the red traffic light (with running engine) and accelerate at green light. Sorry for the confusion, youre right,i have an automatic.

my car has about 40.000km.
autobox oil was not changed. since today.

Sometimes the stuttering occurs 2 times at one gear change. the duration is about 1 second.
I will upload a video and post the link.
There you should hear the strange noise too (LR said the noise is coming from turbo, it is normal and works as designed ).

Do you have these symptoms always or only sometimes?

Hi Alex,

here is the video. next time i will have a passenger to help me to filming
It was a short street so i had to break shortly after the gear shift.



As you can see in the video i accelerate not really hard, but at the traffic light it is a normal for me.
Is it possibly the adaptive gearbox learned my slow driving and thats the reason why it is getting in trouble sometimes?

Same situation with mine, normal acceleration. Clearly audible suction like sound plus judder. And no it is not normal. I hope nothing wrong happens because of that judder or hesitation on 1st gear. We have enough evidence ...

Question is: when the drop in RPM is seen, did you also notice a drop in traction/pulling?
Or the car continues to accelerate, even if the RPM is dropping slightly?
If the later, then it's normal, because of how the gearbox works - the auto gearbox.

How can the car continue to accelerate when the turbo is "coughing" ? It doesn't during the time of juddering.

Hi Alex,

when the RPM drops i can feel that there is a lack of acceleration for a short period of time (about 1 second).

As i wrote in my older post for me it feels that some specific environmental parameters are needed to cause the problem.
I will write down some parameters like ambient temperature, air humidity etc. when the problem occurs and do the same for days where the problem can not be provocated. Hopefully it helps...

I was talking about his particular case. Read the last sentence.
It can't be tell too well from the movie

I know Alex I can hear it because my ear knows how it sounds His particular case is not particular at all. Its how to say ? Common

For starters, if you can log the intake manifold pressure and fuel rail pressure vs rpm and throttle angle would be nice.
With as good resolution over time as possible.
Ideally a graph plot like the ones IID tool from GAP Diagnostics can do.

landmaciej, by his particular case I meant the fact that he has an automatic, not a manual, and on automatics can be seen drops in RPM when the car in fact accelerates. There was the need to clarify this, to eliminate the automatic box.

Last edited by alex_pescaru on 28th Aug 2015 5:29 pm. Edited 1 time in total