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Edited 28 October, 202528 Oct by DavisSehorn

Hello, what engine do you have and what's the problem you're getting?

2015 1.6 TDI Skoda Octavia elegance loss of power at high speeds.

Before I describe the fault here is a little bit of context for the vehicle. The vehicle had a timing chain fitted in March it has been serviced each year and runs fine the engine is quiet there are no weird noises and operation of t vehicle is smooth.

I got the car in September and was told that it loses power on the motorway.

The vehicle was taken back to the mechanic who did the timing belt and was inspected no loose vacuum lines were found or loose fittings. The vehicle was timed correctly.

When you accelerate mainly on the motorway above 3000 RPM about  75 miles an hour the vehicle will start to slow down, your foot can be flat on the gas but the vehicle will still lose speed. It will slow all the way down to 45 miles an hour. Gradually the vehicle will speed back up but as soon as you come to a hill the car has no power and slows back down. This whole time your foot can be flat on the gas. The only way to make the car return to normal is to pull over and let the engine cool for 10 to 15 minutes.

When you lose power the ribs do not jump up but stay consistent. There are no weird smells it just feels like the car is gutless you can tap the gas quickly to get a bit of speed back but that's about it. In my mind it feels like the turbo is stuck open unable to make any boost.

When the fault happens off the motorway the vehicle has absolutely no power to go up hills and has almost stalled there is a small faint squeak that comes from somewhere in the engine when changing gear and using the clutch when the vehicle is in this power loss mode.

This fault primarily happens when the engine is warm and under acceleration. I took the vehicle to two mechanics both of which were unable to find any fault codes, and no warning lights have illuminated on the dash. I have had a clutch and a new flywheel fitted to try and fix this fault. There was evidence of the clutch getting hot, but the fault persists although not as severe.

I have fitted a new air filter thinking airflow may have been restricted this is not fix the issue.

I have driven the car with and without the front assist features, as one mechanic said the brakes could be activating. The vehicle still slows down with or without the front assist.

I've just fitted a fuel filter and we'll see if that affects anything?

The only other thing that I can think of is that the heating is not as good as it could be inside the car and I read on a different forum that guy had a similar problem with an older Octavia 2002 I think where he replaced the coolant temp sensor and the fuel philtre and that seemed to fix the issue. I think that my showed it is the one with the silica bag in the heating system and it does look like that there is sediment in the expansion tank and over this could block up the heater core which would reduce the heat but would it’ cause heating issues and make the car think its  too hot and slow it down.

I have driven previous vehicle in limp mode before, and though you do lose power you are still able to drive consistently. I do not think this is limp mode. But I may be wrong.

If you have any advice for help I would really appreciate it.

Thanks

Davis

Does the temperature gauge indicate overheating when this happens?

Do you monitor the oil temperature on the maxi-dot screen?

Do all the fault indicator lamps show correctly during the self-test before the engine is started?

You say 'Timing Chain' in part of your post - and 'Timing belt' in another, do you know which is correct?

What is your engine code?

Edited 3 November, 20253 Nov by Warrior193
redundant question.

Do any fault indicator lights appear on the instrument cluster when this happens?

• No codes have ever popped up. During the power loss or when driving normal.

Does the temperature gauge indicate overheating when this happens?

• No, it the car gets to temp 90c ish and has never moved past it.

Do you monitor the oil temperature on the maxi-dot screen?

• I dont know how to do that, but I dont see it as an option.

Do all the fault indicator lamps show correctly during the self-test before the engine is started?

• Yes as far as I am aware.

You say 'Timing Chain' in part of your post - and 'Timing belt' in another, do you know which is correct?

• Its a timing belt

What is your engine code?

• CLHA I think.

The car has also had its DPF cleaned in tbe last 8k miles

Does you vehicle have the MFSW ? - On the Mk3, oil temperature can be displayed on the Maxi-dot screen (between the two main dials) by selecting from the function menu.

2 hours ago, Warrior193 said:

Does you vehicle have the MFSW ? - On the Mk3, oil temperature can be displayed on the Maxi-dot screen (between the two main dials) by selecting from the function menu.

You're looking for the "driving data" menu, then you can scroll through the various readings until you find "oil temp"

If you don't have MFSW, then use the rocker switch on the end of the right stalk to find the "driving data" menu, then use the same switch to scroll.

The oil temperature when the engine is at temp. 90ish

Is mid 90s

96C

What reader devices have previous mechanics used when searching for recorded DTCs?

Very suspicious if this fault developed after the cambelt was replaced - but you say incorrect valve timing has definitely been ruled out.

From your description and ruling out valve timing error, it sounds as if the turbo boost valve is intermittently sticking open - although I'd have that would light up the EPC warning and put the engine in limp mode.

Im not sure what code readers were used.

One mechanic is a VAG specialist and he found nothing.

The guy I got to do the clutch got the fault to happen and scanned it but nothing came up.

Which led us to think it us a mechanical fault. Hence the clutch replacement.

Due to no error codes , I dont suspect, turbo, or the injectors.

Update the fuel filter did not fix the fault.

The car did get to a higher speed and recovered quickly but still lossed power.

In will see what i can find out about the valve timing, but wouldn't that effect normal driving?

Its perfect to drive around town ?

I had a similar sounding problem a few years ago on my mk1 1.9 tdi. Car would be fine and every now and then would simply refuse to accelerate properly, peaking out about 70mph despite my foot being on the floor. It got more and more regular and was diagnosed as a failing turbo. New turbo sorted it

13 hours ago, DavisSehorn said:

Im not sure what code readers were used.

One mechanic is a VAG specialist and he found nothing.

The guy I got to do the clutch got the fault to happen and scanned it but nothing came up.

Which led us to think it us a mechanical fault. Hence the clutch replacement.

Due to no error codes , I dont suspect, turbo, or the injectors.

Update the fuel filter did not fix the fault.

The car did get to a higher speed and recovered quickly but still lossed power.

In will see what i can find out about the valve timing, but wouldn't that effect normal driving?

Its perfect to drive around town ?

If the fault had been due to a slipping clutch, the revs would have increased without the vehicle speed increasing - you do not appear to be saying that this was happening.