As the headline suggests, can you permanently disable the ACT system.

The vibration im getting now as soon as it kicks in is quite severe.

Had it in with 2 local vag garages to have a look to see if there is a repairable issue, nothing found.

Popped into one local vag garage and rang main dealer both have told me it can't be done.

Not many returns on Google but some suggest that it can be done

Car is 69 plate octavia 3 1.5 tsi

Has it always vibrated severely when it switches to 2-cylinder mode - or this more recent?

I can't see ACT mode alone causing severe vibration, as it is only supposed to operate when the engine is lightly-loaded. Have you had it scanned for misfires in either of the two non-ACT cylinders?

2 hours ago, Warrior193 said:

Has it always vibrated severely when it switches to 2-cylinder mode - or this more recent?

I can't see ACT mode alone causing severe vibration, as it is only supposed to operate when the engine is lightly-loaded. Have you had it scanned for misfires in either of the two non-ACT cylinders?

Cars done 119k miles , only for last 10k has the vibration been an issue , nothing at all before that.

It's purely when act kicks in it starts , soon as eco pops up on the dash i get the vibration and it disappears as soon as eco disappears

Clearly something has changed then - it's not ACT triggering that is your problem, but something affecting the operational cylinders.

Has a scan for misfiring been done?

Have the sparkplugs and coil packs been checked?

Does the car have a full service history? I agree with Warrior193. Something other than ACT is at the root of the problem.

23 minutes ago, Brian15 said:

Cars done 119k miles , only for last 10k has the vibration been an issue , nothing at all before that.

It's purely when act kicks in it starts , soon as eco pops up on the dash i get the vibration and it disappears as soon as eco disappears

What was done at the last service...

Diagnostics brought up no misfires

Changed spark plugs 2 weeks ago and coil pack a coupke of months ago

No difference at all

I change oil and filters regularly

What did the old plugs look like - especially the non-ACT cylinders?

If nothing unusual was noted with plug electrode colour, I'd suggest a compression test.

A proper diagnosis is going to be required not & not just disabling a major function of how the engine is supposed to operate. Someone who has more than just a Code reader. This might be a 1.5 TSI ACT that actually needs the Cam Belt change sooner than Skoda / VW now say. It certainly needs inspected. The issue could be the anything even cam shaft wear..

^^^This, something has clearly changed (gone wrong) with this engine, as the issue is relatively recent. The 'vibration' is being highlighted when the engine switches to 2-cylinder mode - NOT caused by it.

1 hour ago, Evolution13 said:

A proper diagnosis is going to be required not & not just disabling a major function of how the engine is supposed to operate. Someone who has more than just a Code reader. This might be a 1.5 TSI ACT that actually needs the Cam Belt change sooner than Skoda / VW now say. It certainly needs inspected. The issue could be the anything even cam shaft wear..

Timing belt done around 100k

Been in 2 VAG garages neither of which have a clue

I recently paid £666 for diagnostics etc code came up for purge valve had it changed , no difference

It's how much I keep throwing at it to find the problem

OK, timing belt done. Which might well be the issue. There is a very high possibility of that. Was this a Main Dealer & how much did that cost. £666 bill on diagnostic and was parts, and VAT. Holy camoly. Were they charging for 4 plus hours spent on that diagnosis? I take it this last change of spark plugs were the 3rd set the car had. ??????? Was it part of the Recall for a Software Update? When was that done? Or were the 1.5 ACT Octavia not part of that recall!

Edited 22 January22 Jan by Evolution13

26 minutes ago, Brian15 said:

Timing belt done around 100k

17 minutes ago, Evolution13 said:

OK, timing belt done. Which might well be the issue.

Changing the timing belt on the 1.4ACT and 1.5ACT needs special tools and takes much longer than the non-ACT versions. For this reason the normal cost for a ACT belt change is around £900, how much did they charge you and are you confident they had the special tools needed by the ACT versions?

Edited 22 January22 Jan by PetrolDave

37 minutes ago, PetrolDave said:

Changing the timing belt on the 1.4ACT and 1.5ACT needs special tools and takes much longer than the non-ACT versions. For this reason the normal cost for a ACT belt change is around £900, how much did they charge you and are you confident they had the special tools needed by the ACT versions?

£720 at VAG garage

Edited 22 January22 Jan by Brian15

A quick search on Google suggests that this is a known issue, essentially due to the inherent imbalance of running a 4 cylinder engine on only 2 cylinders. Worn engine and/or transmission mounts are one probable cause.

Another probable cause is that when running in 2 cylinder mode the exhaust frequency changes causing the exhaust system to vibrate against heat shields. Thus exhaust hangers, heat shields and connections should be checked for integrity.

On some VAG cars a loose wastegate rod can cause rattling which can feel like vibration and in cars with direct injection (like the VW 1.5 TSI) carbon buildup on the intake valves can cause rough operation when in 2 cylinder mode. Bearing in mind the high mileage on the subject car in this post, carbon buildup seems a quite likely cause of the problem.

The ACT system relies on oil pressure to activate the solenoids that disable the cylinders. If oil pressure is low, or if the oil control valve is sticking, the cylinders may not deactivate/reactivate smoothly. Depending on the car model driving in sport mode disables the ACT but obviously this is a workaround rather than a solution.

Given the diverse nature of the possible causes it is not at all surprising that 'qualified' mechanics have thus far been unable to determine the exact cause.

Good luck Brian15 - I think you'll need it !!

6.5 hours in the book, and £800-£1,250 on the 1.5 TSI. Some independents as low as £725 for the quote and a couple of members. The Cam Belt change in 2023 for the Schedule change cam as many cars at 5 years old were traded in and Dealers W#were not going to have the job done even if the techs had the £3,000 kit and could do it in 4 hours when not messing about... They were going to have to do 5 year old / 50,000 mile 1.5 TSI ACT,s if customers would rather trade in than pay a Grand plus the other 5 years service items. Cars FMDSH yet not serviced to the Manufacturerw recommendation, specification, schedule or advice.June

£720 was very cheap. It was not OEM kit was it? Is VAG meaning a VW Group Main Dealership? Or VW Specialist @Brian15

Edited 22 January22 Jan by Evolution13

1 minute ago, Evolution13 said:

£720 was very cheap. It was not OEM kit was it? Is VAG meaning a VW Group Main Dealership? Or VW Specialist @Brian15

Vw specialist , these chaps : https://www.vagbolton.com/

Was told genuine parts

Edited 22 January22 Jan by Brian15

I remember you said you had a 1.6 TDI cambelt break before you had this TSI. No luck it seems.

11 minutes ago, Evolution13 said:

I remember you said you had a 1.6 TDI cambelt break before you had this TSI. No luck it seems.

Nope , never have had , made me question if I stick with the octavia for my next car.

Don't know if it makes a difference but car has been used for private hire use for the last 100k

@Brian15 Is it a manual?

2 minutes ago, Evolution13 said:

@Brian15 Is it a manual?

Yes

@Brian15 I was worried there, i thought my memory was going the way of my eyesight and heart and liver. It must be your memory.

21 minutes ago, Evolution13 said:

@Brian15 I was worried there, i thought my memory was going the way of my eyesight and heart and liver. It must be your memory.

That was my previous car, not quite sure what you're getting re: my memory

Edited 22 January22 Jan by Brian15

2 hours ago, Colin1051 said:

Bearing in mind the high mileage on the subject car in this post, carbon buildup seems a quite likely cause of the problem.

Regardless if this is what id9 causing the issue or not probably worth doing anyway.

Quick Google hasn't really helped me, is there a product recommended for a diy job or worth booking in with a garage ?

Edited 22 January22 Jan by Brian15