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I had my Polo 1.2 tsi 2015 model serviced (major) at a VW main dealer on Monday, and the cam belt and tensioner changed. Since then the car is hesitating slightly when the throttle is gently opened.

If you are driving down a gentle incline on overrun at around 1800rpm and gently press the accelerator pedal, the engine ‘stumbles’ or hesitates before picking up. Also if you drive along a flat road at say 35mph in 4th gear, and just feather the throttle to keep a constant speed, the engine runs rough and jerks through the transmission as it alternately hesitates and picks up. It was fine before the dealer had it.

I called today and they are going to have a look tomorrow, but the woman on the phone had a word with the technician and told me that they may have over tightened the cam belt tensioner. I can’t see how that would cause a hesitation or misfire on applying a touch of throttle; the problem feels more like a fuel problem, a bit like a car with a carburettor and choke hesitating when it’s not warmed up properly, and the choke has been pushed in too early.

Would anyone have any ideas, comments to make, please?

I've read about this sort of thing happening when getting the cambelt replaced on that engine type, not good and makes me worry about when I eventually get the belt changed on my wife's August 2015 Polo 1.2TSI 110PS - these belts don't need changing this early unless they have become damaged for some other reason, but that is cold comfort for you!

The comments made would just be something said in way of an excuse, so when they open it up I'd hope that they find that the timing is slightly out, or some other connected to this belt change task, that is reversible.

Good luck, let us know what the outcome is.

maybe they update software on the ecu ?

Well I took the car back to the dealer, and before they even looked at the car, they said the ‘timing’ my might be out. I had to press them as to what timing they were referring to (valve, ignition, or fuel injection), and they said they meant the cam belt timing.

They had a look, road tested it, checked for fault codes and although they could find nothing wrong, they slackened the cam belt tensioner slightly, and confirmed that the timing was ‘spot on’.

The car is better, although not perfect, there is still a slight hesitation when feathering the throttle, and I’m sure it wasn’t there before they had it. I can’t help but wonder if they have left a sensor disconnected, or an air pressure reading pipe off somewhere, but I can’t see anything wrong, and if that were the case, I’d have thought it would put an engine management light in and have generated a fault code for them to read.

Well I took the car back to the dealer, and before they even looked at the car, they said the ‘timing’ my might be out. I had to press them as to what timing they were referring to (valve, ignition, or fuel injection), and they said they meant the cam belt timing.

They had a look, road tested it, checked for fault codes and although they could find nothing wrong, they slackened the cam belt tensioner slightly, and confirmed that the timing was ‘spot on’.

The car is better, although not perfect, there is still a slight hesitation when feathering the throttle, and I’m sure it wasn’t there before they had it. I can’t help but wonder if they have left a sensor disconnected, or an air pressure reading pipe off somewhere, but I can’t see anything wrong, and if that were the case, I’d have thought it would put an engine management light on and have generated a fault code for them to read.

Its possible that there is air in the cooling system !
They might not have purged it properly !?
I had a similar problem on my golf gti so i undone the expansion cap put the heating on full heat then turned the engine on & let the car coolant get to temp , once it was at temp i put the cap back on & it seemed to sort the issue .
But ive noticed that on the newer vw’s a code will come up on the diagnostic saying about coolant issue but its only coz the cap was off whilst the engine was running so not a problem .

Update:
The car went back to the dealer yet again, and on the way there, the hesitation / misfire manifested itself, so I held the throttle in the ‘just open, feathered position’ so that the shunting became worse and worse and eventually the engine warning light came on.

The dealer was able to read the fault codes which diagnosed faulty coil packs on cylinders 1&4. They swapped those coil packs with those on cylinders 2&3, and now the car is fine.

I’m still unsure as to how that could have made a difference, unless the coil packs are breaking down and moving them around has hidden the faults in some way, or improved the electrical connections, which were less than ideal.

Of course another possibility is that they had made an error with the service of some kind, which they have discovered but are unwilling to admit to, and the coil packs story is a cover story.

From what i understand,regarding the hesitation. It sounds like coil pack/coils/cables.
I have the same common sense, regarding the swapping. I do not understand aswell how swapping could fix a problem , the only thing it could do is identifying the problem.
But the problem will be moved to the other cylinders.

Also common sense says that they should have the error codes the first time you sent it to recheck it unless you didnt have any lights pop up then.

Dont you have any obd yourself like obd11 etc. I have one and it helps in the sense that they cant really s**t me when i go to a garage. I can see the codes , google them etc.

Retali wrote: Fri Nov 11, 2022 9:06 am From what i understand,regarding the hesitation. It sounds like coil pack/coils/cables.
I have the same common sense, regarding the swapping. I do not understand aswell how swapping could fix a problem , the only thing it could do is identifying the problem.
But the problem will be moved to the other cylinders.

Also common sense says that they should have the error codes the first time you sent it to recheck it unless you didnt have any lights pop up then.

Dont you have any obd yourself like obd11 etc. I have one and it helps in the sense that they cant really s**t me when i go to a garage. I can see the codes , google them etc.

Yes, same here, to really make best use of that cover story, they should have sold and fitted new coils on cylinders 1 and 4 - just telling that silly story makes them look a bit silly.

Also, last thing that I always do/did when getting dealerships to service cars that are under warranty, is/was to read the fault codes and save a copy of them and leave them still logged in memory, and same after getting home with the car.

Hi there everyone. Anyone knows what the problem here was? I had taken my 2015 polo tsi in for timing belt service and now sitting with the exact same problem! A bit of a back story, after the belt was replaced, I experienced missfires on idle but no fault codes! Engin would idle smoothly and suddenly surge, you could feel the whole car shaking and then this would happen every 14 seconds or so... The mechanic redid the timing which resulted in an improvement bit the car was still idling rough! After returning the car for a 2nd time, the mechanic insisted that the timing was correct and suggested new coil plugs and injector testing which car came back clear , a bit dirty but had them cleaned and surge continued! Next was coil packs, now a smoother idle but the car missfired on low exeleration in high gear, such as keeping a steady speed and refs @ 2000.
Returned the car a 3rd time,threw a fault code running rich and this time the owner of the RMI registered workshop did the timing himself and informed me that the car is running smoothly now, but timing was spot on and no changes was made. Did compression test , came back clear.
After driving the car for 2 days the same rough idle continued but the car was driving smoothly now, at this stage ,I replaced the fuel filter myself over the weekend which has never been changed, 79000kmh on clock and the petrol inside was black brown with noticeable granuals of dirt! Car went back again as the new filter made no difference and apparently they found that the spark plug gaps were set to 0.3mm ,adjusted these to 0.7mm and the idling has improved with 90% ,runs mostly smooth, or not rough enough for a workshop to see fault except now i have this same hesitation when driving ! From my personal knowledge, I believe the car ran much smoother before all these new parts were installed and thousands spend on repairs. I'm at a lost financially and can't pay to have VW redo the timing a 3rd time..any help would be appreciated.

Also full service was done.
Waterpump replaced
Coil packs.
Injector tested and cleaned
Leak down test came back clear.
Compression test came back clear.

Here we were reflecting on the change of the timing belt in the EA211 engines. viewtopic.php?p=600330#p600330
I wrote my final conclusion in blue. viewtopic.php?p=600340#p600340

In the most current 'Evo' engines, the opening and closing angles of the valves/cams are even coded during the camshaft manufacturing process, that is, two identical engines are not the same and cannot share these parts. https://www.youtube.com/watch?v=wavP8h1rKg8

Coming back to this issue, the car is basically the same, and Ive sort of learned to live with it; since I generally only use it for longer motorway journeys, its not too bad.

However Ive had another idea, could it be a problem with the Mass Airflow Sensor? No idea if they might have disturbed it at the dealership when they did the cam belt, but Ive been reading that if faulty, they can cause a wide range of problems, including rough running and hesitation.

Any opinions, and how could I test it please?

Shirespeed wrote: Wed Oct 16, 2024 3:26 pm Coming back to this issue, the car is basically the same, and Ive sort of learned to live with it; since I generally only use it for longer motorway journeys, its not too bad.

However Ive had another idea, could it be a problem with the Mass Airflow Sensor? No idea if they might have disturbed it at the dealership when they did the cam belt, but Ive been reading that if faulty, they can cause a wide range of problems, including rough running and hesitation.

Any opinions, and how could I test it please?

I do not have the same polo as you, but does it really have a MAF sensor ? Or MAP sensor ? If the part number is 03C906051F it is a map sensor.
Usually when these things have problems, give certain codes and usually force limp mode (at least in my case) .
As i have told u in the past, you should get an OBD scanner, if the map sensor has problems it will give some fault codes.
And yes one of the problems is hesitation since the air pressure is not good. Also you run expensive. Not good gasoline consumption.

So almost 4 after my OP, I have an update on the misfire which developed suddenly after having my Polo serviced at a main dealer.

I read in a couple of places about mid range misfires which could occur when using NGK spark plugs, one involving a 2 stroke race bike and another with a VW Polo, which mentioned that it was always best to use genuine VW Bosch plugs. I had learned to live with the misfire on my car, but having learned this, and since my plugs were probably ready for a change (40 months / 25000 miles) I bought 4 new genuine VW Bosch plugs and fitted them to the car, removing as I did 4 NGK plugs.

And the problem is solved, just like that the car runs perfectly, just as it did before I entrusted it to the main dealer for the service. Im a bit annoyed to be honest./ Shouldn't they know about this, and even if they dont, shouldn't they service the car with genuine VW parts?

Shirespeed wrote: Sun Mar 22, 2026 10:25 am So almost 4 after my OP, I have an update on the misfire which developed suddenly after having my Polo serviced at a main dealer.

I read in a couple of places about mid range misfires which could occur when using NGK spark plugs, one involving a 2 stroke race bike and another with a VW Polo, which mentioned that it was always best to use genuine VW Bosch plugs. I had learned to live with the misfire on my car, but having learned this, and since my plugs were probably ready for a change (40 months / 25000 miles) I bought 4 new genuine VW Bosch plugs and fitted them to the car, removing as I did 4 NGK plugs.

And the problem is solved, just like that the car runs perfectly, just as it did before I entrusted it to the main dealer for the service. Im a bit annoyed to be honest./ Shouldn't they know about this, and even if they dont, shouldn't they service the car with genuine VW parts?

Bosh spark plug for this engine ?

According to ETKA, the only part number for the 1.2 TSI 16V EA211 is 04E905601B, and they are NGK.