Looking for any help. I have an Octavia 05 elegance 150k. It’s automatic with dsg gear box. All well until six months ago. Speeding up to join motorway the gearbox wouldn’t go above 50mpg. Nurses it to next services. Switched engine off and on and problem was gone.  Just last week same thing happened. Happy to get to fourth gear then no more power. Sitting at 50mpg. Again switched off and on and alll back to normal. The box and engine runs smoothly with no noises. Is it a glitch?  Or is it the beginning of the end of the gearbox?  Anyone any ideas?

When was the oil in the gearbox changed last? Should be every 40,000 miles from what I read recently on here. I assume you meant mph not mpg.

Edited 1 November, 20187 yr by pikpilot

Thanks for getting back.  I change the oil six months ago, after it happened the first time. And yes I did mean mph. 

What about if plugging in an scan tool to see if anything has been recorded and having to start from something?

Edited 1 November, 20187 yr by AkisVH

Thanks.  That’s a very good idea.  

Sounds a lot like turbo overboost protection?

Chrisund123 I think you’re right. I was flooring it to get onto the motorway. I’ll look that up. Thanks   

Maybe a vane/valve controller could have been stacked or not working properly?

Yeah sticky vanes is quite likely. Try the Mr muscle cleaning trick?

Akisvh and Chrisund123 thanks for the suggestion.  I’ll definitely check it out. Thanks your feedback. Really appreciate it. 

Presuming it's the pd diesel then you first need to test the vacuum system that runs EGR , turbo vanes, and anti shudder valve. It can spring a leak with the numerous flexi hoses or one of the thin hard plastic hoses can be rubbed through due to the diesel vibration (I had this a while ago). The whole thing starts from a vacuum T connection taken from the brake servo vacuum. A clue can be when the anti shudder valve stops working - when you turn the engine off does it shudder?

Hi bigJohn. You have given me a lot to check,  appreciate that.  In answer to your question, no the engine doesn’t shudder when switching off. Alls as it should be.  

6 minutes ago, funkydude said:

Hi bigJohn. You have given me a lot to check,  appreciate that.  In answer to your question, no the engine doesn’t shudder when switching off. Alls as it should be.  

 

Always worth checking vacuum system first though - before you start disturbing/ chucking money at turbos. I've know people replace turbos to later discover the original fault was just a small hole in a pipe!

Thanks bigJohn, rest assured I won’t be spending on the car anymore.  I’ll check out the system as suggested. Thanks again.  Big help.