UK-POLOS.NET - THE VW Polo Forum

It's been a while since I posted anything but I am still having problems with my Polo. Over the last year it has been into the local VW dealer 5 times and the fuel pressure sensor, water pump and belt tensioner have been replaced but nothing has changed the problem I have.
Basically some days the car runs brilliantly, it is quiet, smooth, responsive and good mpg. Other days it is noisy (injectors), rough, lacking in power and poor mpg. Good days see mpg figures of 60-70 (even into the 80's on the odd occasion), bad days it is 40-50 mpg (even 37 on one occasion!). Generally when it is bad it idles at about 980 rpm and when it is good it's 820 rpm. The dealer says they have done extensive tests and the conditions I experience are 'normal' but clearly they are not. It is not down to DPF regeneration as it is obvious when this happens and the 'bad' conditions can last for 7 or more days. I do not use the car for commuting and it has a good run at least once a week. I have not had a single warning light since owning the car (13 months), other than when the fuel pressure sensor failed.
I have two questions.
1. Has anyone out there experienced similar problems?
2. Has any one any suggestions as to what the problem is?
Thanks in advance, any help would be appreciated.

Hi,

I own a 2016 TDi 1.4 and experience similar issues. My commute to work is quite long and involves a lot of "A" road and potentially motorway driving so they iron themselves out quicker.

Personally, I've put it down to the DPF. I figured the DPF was happening when the fans were at full chat (amongst other things) but sometimes they're not on and the same symptoms persist.

According to the manual, a DPF regen should take 15 mins at 43mph in 4th. So my 20mile commute on the motorway and A roads at 55-70mph should be no problem but sometimes for 2-3 days in a row I experience issues like you describe.

- High idle - 1000-1100rpm
- Stop start refuses to work
- Poor MPG
- Sluggish pulling away in 1st

I can maintain 75MPG on my commute usually and when these issues arise, I'm lucky to hit 60 and more often than not it can be mid 50s.
I've learned to detect when this happens very quickly and adapted my driving to maximise my economy.

Just some Q's
How far do you usually drive in your Polo?
What sort of speeds?

Hi skymera, thanks for replying.
My journeys vary alot and can be as little as 4 miles on an odd day but generally I would say 10 miles per journey would be fairly common and when I am on the open road speeds of 55-65 mph are usual. At least once a week it has a reasonable run out of about 30-40 miles. I appreciate what you say about DPF regeneration and, like you, I have got to know when regen happens but most occasions there are no signs of it, no fan running, no warning lights etc. I have a OBD2 device and one of the parameters it monitors is exhaust temperatures. When a regen is taking place it records a temperature of approx 600 deg C. but at all other times it's about 200 deg C, if anything it is slightly lower when it is running badly. I get all the symptoms that you get but they can last over 7 days, even when I have been on the open road/ motorway. To give a good example, I went to Cornwall this year, a distance of 250 miles and the car ran ok. The following morning it idled immediately at 980 rpm and was rough all day! Every time it goes into the dealer they say they do not experience the problem, which I find very odd. The other odd thing is that the problem did not occur, at all, between April and September and does suggest that it may be temperature related!