TDI 170 misfire resolution.

[Trevor M]

In case it may be of use to others I thought I would document my experience relating to my 2013 TDI 170 misfire.

 

To my dismay, after having owned the Yeti from new in 2013, it recently developed a misfire when accelerating mildly for around the first half mile from a cold start, although cold idle seemed ok. Once it was warm it appeared to be fine. The misfire seemed to me to have been similar to that experienced on a petrol vehicle with a defective ignition relating to one cylinder. Searching around the web it looked as if there were many possible causes for this, so out came the trusty VCDS. No error codes were set ( I should explain I am neither a diesel nor a vcds expert,) so again I needed to educate myself a bit in these areas.

 

Using 'Advanced Measuring Values' on VCDS and logging the results showed that the fuel rail pressure was following the specified value fairly precisely, and the boost pressure ( I think that is the right term) looked to me as if it was ok. However, the Injection Quantity Deviation mainly for cylinder 2 was rising to 3mg/Litre (appearing to be compensated by the others) when driving from a cold start, but settled within specification (difficult to dicscover precisely for the CFJA engine, but for some seems to be around +/- 2.8mg/stroke) when warm / hot; this suggested a problem with cylinder 2's injector or something in that area. I have to say I found the VC-Graph application that ships with VCDS less than user friendly, and actually used a spreadsheet (OpenOffice) to 'chart' the results logged in the VCDS .csv files; the charts produced were I think a good indication of what was happening with the Injector Quantity Deviations, although as the ECU seemed to be adjusting these to compensate for one another I was not entirely confident that my suspicions about Cylinder 2 were correct. I had already checked the glowplug resistances as these had been suggested by a friendly mechanic, although I thought these would have potentiially caused difficulty starting and rough idle rather than the symptoms described above.

 

To cut a long(ish) story short, I booked the car in with a diesel specialist in Norwich (Allstart Diesels, with whom I should say I have no connection) who removed an tested the injectors and confirmed that indeed injector 2 was faulty as shown by a leak back test, although all injector spray patterns were good on the bench.

 

New injector fitted (I declined the rather expensive option of replacing all four) and all now ok!

 

Having learnt a bit from this experience and following a few searches on the web, I think for any similar issues I would purchase a leak back test kit to confirm the VCDS findings.

 

Maybe should add that Allstart also checked the fuel pump for contamination in case that had led to the injector failure, but all was ok.

 

Enough of my ramblings, but if this is of any use to others it will have been worthwhile.

 

 

Edited 2 February, 2023 by Trevor M
mg/Litre changed to mg/stroke

[Carlodiesel]

I wonder why it always seems No.2  Injector problems on VW group cars.

 

I replace an Injector No 2 on a VW golf last year (1,6D) & most of Golfs seem to have problems there. 🤔

[wexti]

I replaced all 4 as I was told that the others would fail as well, did yours ever give any more trouble?

Edited 19 February, 2023 by wexti

[Trevor M]

Hi wexti. All is still going well with mine, but bear in mind the problem was resolved less than a month ago. My decision to replace only the failed injector was partly due to the cost, but also the vast majority of injectors can go on far longer than my current 80,000 miles. The reason for having the system checked for contamination at the same time was for reassurance that this had not been the cause of the problem (and hence could have also had an effect on the other injectors.)

[J.R.]

On 02/02/2023 at 08:37, Trevor M said:

Enough of my ramblings, but if this is of any use to others it will have been worthwhile.

 

Not ramblings at all, very usefull fault finding and diagnosis information, thankyou!

[fuzzybunny]

Thanks for this, I have the 170 as well, all OK so far after 80,000 miles.

Will keep a look out.