Throttle shuddering??

[Adotparker]

Good evening fine people!

I'm experiencing a frustrating issue with the 2006 1.4 petrol. When you're cruising eg 1500-2000rpm, and barely using the accelerator perhaps if you're cruising down a hill - I feel a jerkiness in the throttle, as if tapping the throttle in spikes. Kind of a shuddering? Tickover is fine, and acceleration is fine. I've cleaned the throttle body, and changed the accelerator pedal - therefore the position sensor, and the air sensor. I've also changed the plugs and cleaned the coils, cleaned the PCV ( also checked that the PCV is working ) The last thing I've got to change is the fuel filter could it be the fuel filter or is it something else? a more regular Italian tune-up?

Does anyone have any ideas? It's done 62,000 and had a recent oil and filter service.

Thank you very much!

[littlepolo]

Did you do the throttle body alignment/calibration using the VAG tools?

[Adotparker]

Thanks for the reply,

No, I didn't calibrate it. I simply removed it and cleaned out the excess dirt. - there wasn't a lot.

[littlepolo]

Suggest checking the DTC codes

[Adotparker]

The only DTC displayed is a live and historical A/C pump-related issue. - That's from a reputable diagnostics scanner too, not an eBay plug-in.

[littlepolo]

I'd do a TB alignment to rule it out.

Old Polo electrics can do very odd things too, but I've not heard of wayward throttle.

[RUM4MO]

I've had that stuttering/mild shunting/hunting on my wife's previous 2002 VW Polo 1.4 with the BBY engine, I started using UL+ petrol and that sorted that out, that car was also pinking/pinging at low revs and highish load - eventually even when cold and in winter time, replacing the oil separator sorted that out and much reduced its engine oil use, but my wife would not allow me to backing back to using normal UL petrol as she had got used to the much improved driveability that came with using UL+!

I suspect that the TB gets recal'd at every hot engine stop, and even her 2015 VW Polo 1.2TSI 110PS makes lots of TB movement noises after a hot engine stop - easy to hear in the confines of the garage!

Oh, and I even replaced the EGR valve with a NOS one bought cheaply via ebay - and carried out "basic settings" on it as well as the TB after cleaning it in situ and fitted a cleaned by me but used MAP sensor, neither of these last two activities changed anything that I could detect - all that was prior to replacing the oil separator and starting to use UL+.

[littlepolo]

I did the same, but do not recall the throttle response ever being as the OP described. I'm very familiar with pinking on the BBY, and how it makes an appearance under load or in warmer conditions. Currently, I use an Ethanol booster which has taken care of that (it's cheaper than using premium fuel).

[Adotparker]

Thanks all,

Having replaced my Fuel filter, running down the tank to 1/4 and adding a full bottle of Dipitane to the tank... all problems have gone away! noticably smoother throttle and no shuddering.