1.4 FSi Misfire Codes

[lonkers1968]

Hello to you all..!

I'm new to this forum and to Polo ownership, although I've owned a Seat Ibiza 1.4 Formula Sport from new in 2007.

My son has just bought a late 2005 Polo 9N3 1.4 FSi Sport (with a little help from us!).
It's got a fully stamped (VW) history and on average has covered about 4,500 miles a year. It's now done 46k miles total.

The supplying trader is not the most customer-focussed chap in the world and I am struggling to be even bothered to speak to him again - after all the car is over 10 years old and you takes your chances and that....

We took the car for a long run yesterday and it ran like a dream - cruised well at all speeds, including a good stretch of 70mph+ on the motorway (nothing too illegal though - all sub-80mph!).

Sadly, whilst pootling around, the car suddenly began misfiring - I was about 60 miles from home at the time, but managed to limp it home on two/three cylinders. Somewhat of a challenge at roundabouts and hills.......!

We got it to my local VW/SEAT Specialist who plugged in the diagnostic equipment and it came up with various error codes:

16684/P0300 Random/Multiple Cylinder misfire detected
16685/P0301 Cyl.1 Misfire detected
16686/P0302 Cyl.2 misfire detected.

17479/P1071 NOX sensor heating control - implausible signal.

The misfire stopped before the diagnostics (typically) and has driven fine (so far) since we left the garage.
I'd driven 60 miles on a misfire, then switched off at the garage and as soon as they fired it up again, it ran normally!

Help...!

The VW Specialist suggested I reject the car (I am within my 30 days of purchase) and buy another non-FSi Polo - he reckons the FSi is temperamental.

Sadly, the car is otherwise in such great condition that I am now in a difficult situation, so would welcome any ideas or similar experiences any of you might have had.

Shot in the dark, I know, but would really like to keep the car. However, if opinion suggests they are not reliable then I'd rather bite the bullet and get rid whilst I can.

Cheers. Graham.

[alexperkins]

Welcom Graham

The 1.4FSI had a very short life in the polo, partly because it was expensive to produce and did have some reliability issues though there were ironed out and the FSI overall provides good power and economy.

The misfires are likely due to failed coil packs which FSI engines of that era chewed through (they have since modified the coil pack and they last longer now)

As for the NOX sensor heating control error, that could be slightly more serious. Could be due to a faulty lambda sensor

I would speak to the dealer, and get him to cover the cost of repair. The dealer does have a responsibility to resolve the issues as its been sold to you in good faith and that all is in order.

[lonkers1968]

Thanks Alex - apologies for the delay replying.

Your thoughts mirror those of my local specialist VW service centre (A&A Motors (Yorkshire) Limited), with whom I have the utmost faith.
The supplying dealer is very much stuck in the '70's and the likelihood of him rectifying the faults satisfactorily is small.
It's likely we will return the car. It's a pity because it really is a well cared for example - but these engine issues have dented our confidence.

We are told a standard 1.4 is the better option - so will see what's out there.

I have a SEAT Ibiza 1.4 Formula Sport (non-FSI) bought new in 2007 - goes as well today as the when I bought it - hence our wish to go down the VW group route.

Appreciate your input.
Cheers. G

[lonkers1968]

Bit of an update....

We decided to keep the Polo 1.4FSi and deal with any issues as they occur.
First job was the air-con and it was resolved by going to my local BRIT Tyres depot and having a full system check and re-gas (1.5 hours!) for £21.90 (offer at the time).
Works a treat now - cheap repair.

The NOX sensor continues to be an issue and your thoughts would be appreciated.

We've bought a basic code reader / reset tool and now monitor the fault.
Generally it is 17441 (low signal) and sometimes 17479 (implausible signal).

I've had a quote of £250 from my local VW Specialist to replace the NOX sensor; the part is around £150 on the web. (VW want £310 + £95 diagnostic fee).
Presumably replacing the sensor will resolve the problem?

Has anyone ever replaced a NOX sensor on a 1.4 FSi and if so, is it as straightforward as it seems?
I can see the two sensors (top one is Lambda (cheaper) and lower one is NOX) but they are not one and the same (or interchangeable) as some forum writers would have you believe!
The Haynes manual does not cover this engine so I'm working blind - where does the NOX sensor electrical lead connection happen? In the engine bay or within the car?

Having said all of the above, will we kill the car if we don't replace the sensor?
It seems to run fine, but then I've only ever driven it in this state so don't know if it's performing badly or not!

The joys of older (modern) cars! Give me set of points, distributor and carburettor and I'd be happy!!

Thanks for any assistance you can offer us.

Cheers!