A2 3L 1.2 tdi stays on idle when shifting gear..no throttle action unless restarted??

doennes

Member
Ok,

A2 1.2 with automatic gearbox, when the car shifts gear, it cuts throttle and go to idle, then as soon as shifting is complete, throttle is applied again. This is how it works from the factory.
I now have a problem, usually when car is cold, it can happen 2-4 times before it stops happening, there are also days where it doesnt happen.
Car shifts, cuts throttle, and car stays on idle, i.e you loose all power,pumping throttle does not result in anything.
The mechanism that cuts the throttle (electric I guess) is still active.
The only fix is to switch car off, start, and it works as it should. It can then re-occur after 5-20 minutes, restart needed.
On highway, I can put gear in neutral, switch off car, and lightly press the brake and restart while rolling without power, put gear in drive and continue, but I do not like to do this to be honest..
Can anyone help with this? What part should i focus on?
This might have started after I took off the hood and pressure washed the engine bay a month ago.
All help is highly appreciated.
 
Have you checked the hydraulic oil level? If not, unplug the pump unit and with a 24mm spanner, unscrew the accumulator (black sphere-like and part of the pump unit) half a turn. Check the oil level in the reservoir (translucent container with a green cap). The level should be within the marked rectangle. If not top up with VW hydraulic steering oil. Re-tighten accumulator and plug in the pump unit. You are finished, apart from finding the source of the oil loss.

If the oil level is OK, although the exact symptoms suggest the former cause, it might be due to a faulty sensor on the gearbox. In that case the fault will occur without a gear change being made. The sensor measures the speed of the output(?) shaft in the gearbox and compares it with the engine speed. Depending on which gear you are in, if the ratio is not correct, the system will assume that the clutch is slipping, open the clutch and close the throttle. This happened to me once in the fast lane of a German motorway going uphill and at night! Usually it is caused by a faulty sensor or a poor connection, probably at the sensor. The sensor is on the top of the gearbox and can be reached from the wheel arch without removing the bottom cover. The sensor is held in position by a single 6mm screw.

RAB
 
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Thanks for really good info there, I will check it out this week and give you an update. When you say unplug the pump, does that mean some electric connector on the pump unit attached to the accumulator? I havent had a look at that area yet.
 
I notice you are in Norway. I noticed my pump making the normal noise, then slowing down considerably, then speeding up before reaching pressure and switching off, only when cold, just after start up, idling. I switched the car off before it warmed up, changed the oil in the pump, and this cured it instantly. I will probably change the oil again in a few months. To do this I removed the pump, turned it upside down (lots of dark oil came out). I couldn't get a pipe in the oil container to suck out the old oil. Temps were dropping to around 2 or 3 degrees recently.

If your oil in the gear shift actuator pump hasn't been changed for 3 years or so maybe it is time anyway.
 
It's a good idea to check the drain from the plenum cover (at the base of the windscreen) at the LHS to ensure that is secured to the cover (with a spring clip) and that it is not blocked. This will help keep water away from the hydraulic unit, which is next to the drain.

Here's a link to a someone with a similar problem: http://www.a2oc.net/forum/showthrea...h-pics-and-Fluid-question&highlight=hydraulic

RAB
 
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Ok, did some investigation today, but did not have much time.
Status of car: Problems is getting worse, it can now happen 10 times on a 30 minute drive, so car is almost in the "not-usable" category. Also, it seems it can now happen even when it is not changing gears; Loose all power/throttle, car goes to idle, need to restart for throttle to work.

I have ordered a new accumulator, I bought the gear oil yesterday.
Opened the hood today, checked oil level in tank, it was slightly below the marked triangle (?). Did not have time to do the "remove accumulator test and check oil level", but filled about 1 deciliter of oil. Drove car, all the same, it "died" many times on a small 10 minute trip.
Doing the manual shift test, the pump starts everytime I change gear, and runs for a few seconds (1-2 sec) between gear changes.
Not sure what the oil level will show if I loosen the accumulator, oil tank was now almost full after I filled it today, can there be too much oil in there?
Does it still sound like a oil or accumulator issue, or something else? I will change accumulator as soon as I get it.
 
I notice you are in Norway. Temps were dropping to around 2 or 3 degrees recently.

If your oil in the gear shift actuator pump hasn't been changed for 3 years or so maybe it is time anyway.

Yes its been colder lately, and so far the problem has been worse when temp gets lower, not sure what it indicates. Can you explain more on how to drain oil in the pump? If I suck out the tank, will there still be stuck bad oil in the pump, or will this "thin out" quickly with the new oil I put in the tank, leaving the oil in the pump fresh? (I.e is there a constant replacement of the oil in the pump from the tank when car is running)
 
doennes,

This diagram from the Self Study doc 218 referenced in post 84 in this thread should clarify your question:

Oil.jpg

Steve
 
It's almost certainly an accumulator problem. The accumulator is filled with nitrogen over an elastomer diaphragm. Over time the nitrogen leaks away. Don't overfill the reservoir; the level shouldn't be above the rectangle mark with no pressure, i.e. unit unplugged and accumulator unscrewed half a turn.

RAB
 
Ok, progress..Today changed actuator. No change in fluid level in oil tank when unscrewing old accumulator, it was a the rectangle mark. Removed and sprayed connector to oil pump unit. Fitted new accumulator.
Did the change gear test without car running. Could now to 4 upward gear changes before pump started, 3 downwards. Took the car for short trip, no problems detected. Will try for a longer drive tomorrow.

Thanks for all help so far!
 
Status:
After changing the accumulator, car has been in use everyday, gearing is good.
The problem I now see, is that when car is cold, it will take up to 10 seconds from when I turn the key to start the car, until starter engages and starts the car.
I guess it needs to build up some pressure or something in the hydraulic. Now what is the fix for this?

Thanks for help so far!
 
The engine won't start until there is sufficient hydraulic pressure to operate the clutch and gear actuators. This is normal.

RAB
 
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