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Just wondering if I can get some feedback on what the problem with my car could be.
The problem:
1. The transmission doesn't downshift when slowing down then speeding up while cruising on the highway. For example, I am cruising at 100kph, slowed down to 60kph then speeding up again, the car struggle to rev because it's stuck in the highest gear.
2. The transmission won't upshift when I am accelerating from a complete stop. For example, when taking off from the red lights, it would be stuck in the first gear for a long time and wont to shift to second gear until it gets to around 4K+ rev.
3. When the issue occurs, the shift paddles won't work. Can't manually change gears with the paddles.
The issue is intermittent and usually, occur after an extended period driving (20 to 30 mins) and usually after cruising at a constant speed. Start-stop driving doesn't seem to trigger it.
The problem goes away if I shut off and restart the engine again (not start-stop feature but ignition switch off and restart). But will come back quickly until the engine is shut off for an extended period.
There was no fault code when then mechanic hooked it up to the diagnostic machine. The mechanic did an oil and filter change and reset the transmission (well he told me he did anyway).
My thinking is that it must be an electrical issue considering it's intermittent and goes away after a restart. So it could be a throttle position sensor not working when the engine is hot (I notice that it's worse during hot days and longer drive time).
or worse it could be the conductor plate. Don't think it's mechanical because it works fine for shorter distance driving.
Does anyone have a similar issue and was able to fix it?
I had almost identical issue that you stated. It turns out is nothing to do with my transmission and it actually my intake manifold motor that control the swirl flaps acting up.
For my case, because the manifold motor was intermittently fail, which caused the engine lack of air. The swirl flaps stay close in the default position. Because the engine is lack of air, it puts the transmission in limb mode,
I had my tuner disabled the swirl flaps and made the flaps stay open permanently. This saved me 4k since that how much mb dealer want for a brand new intake manifold
You can try the adaptive shifting transmission reset:
1. Turn the key to position 2. You should see all the dash lights come on. Do NOT start the car. Position II: You should hear two clicks and all your dash lights should turn on. Do not start the engine.
2. Press the gas pedal all the way. By pressing the accelerator pedal to the floor, you will activate the kick down switch. Keep the gas pedal pressed all the way to down.
3. Wait. Continue to keep the gas pedal pressed for at least 10 seconds.
4. Turn key to OFF, position 0. Don’t remove the key. Some models may need the key to be removed.
5. Release the gas pedal.
6. Wait 2 minutes. During this process, key is left in the ignition in the OFF position.
7. Start the car and drive.
Once you perform this procedure the Engine Control Unit (ECU) and Transmission Control Unit (TCU) will work together to learn how you drive by monitoring your driving pattern. After you follow this programing method of the TCU / ECU drive the car for 15 min. Do not race the car, unless that’s how you plan on driving all the time. You should have a transmission that shifts smooth and normal.
I think I narrowed it down to the accelerator pedal sensor but not sure how to fix it.
I checked the live data with a scanner while driving and the issue occurs when the accelerator pedal sensor value was stuck at 20%. This is the live data under the Shift Program. However, I checked the live data under ECM the accelerator values seem to be fine (ie it's not stuck). So could be a communication issue between the units.
I think I found what the problem was. A split in the intercooler pipe hence the car was running like a truck all this time. Installed a new pipe and the issue seems to have gone away and the car running a lot smoother. However, what I noticed when changing the pipe over there was a lot of oil in the air system. There's oil in the turbo inlet and out from the intercooler. I know that there is supposed to be some oil, but how much is too much?
10-16-2019, 04:46 AM
