Mr.W

Hey,
I'm new to the forum and also recently become the proud owner of a 2014 A6 C7 3.0 TDI. Unfortunately things haven't got off to the best start though and I am having trouble diagnosing the issue, any advice or help would be greatly appreciated!

The issue
On a cold start I noticed a very slight missfire coming from the engine that lasts for around 10 seconds and stops, There are no warning lights, no smoke, no knocks rattles or any other issues. That said the car has just surpassed 100k (only just) so I plugged in my OBDeleven reader and scanned the car for any faults. I got back the error code P067F00. I thought I would start with the obvious thing as the cars hit 100k and replace the glow plugs, thinking one had died. After some wiggling back and forth, lots of WD40 and a few deep breaths later I successfully changed all 6 plugs without snapping any (yay).. Unfortunately though the next morning I felt the exact same missfire which again lasted around 10 seconds and stopped... Getting a bit anxious at this point that this was a more serious problem I plugged in my OBDeleven reader again and scanned the car, sure enough it returned the same the fault code - P067F00 Glow Plug Circuit High Cylinder #6.

Since then I have been researching any common issues and supprisingly found nothing or very little. I tested all 6 glow plugs with my multimeter and were all around 1.6ohms to rule out a fault there. A mechanic friend said it may be the glow plug relay or control module - I have been unable to find anything indicating where that might be located on one of these or if that could even be a cause for an issue with one Cylinders specifically. I've cleaned all the connectors and glow plug tips with electrical contact cleaner. A little bit stuck at this point and looking for any advice or pointers really, or to see if anyone else has had a similar issue?

Cheers!

Audi A6 Saloon, 2014 3.0 TDI (204bhp) - 101,000 miles

IlirianR

My 2015 A8 TDI does this but only when I don’t let it warm up for a minimum of 5-10 seconds. If I start it and put it into gear it does it 6/10 times. Usually when I let it run for a second it doesn’t. Not sure if its tune related since I run the APR tune for the TDI. When I go in for service I’ll have them check it out.

Mr.W

Deffinately get it looked at. I plugged an OBDeleven device into my car which showed me the fault with the glow plug circuit. It could just be tired old glow plugs that aren't heating up the cylinder correctly on startup.

It'll lead to a rough idle and potentially more issues down the line if left, glow plugs also help make the ignition on a diesel engine more efficient. If you notice a strong diesel smell after startup from your exhaust that could also be a sign of a bad glow plug or circuit due to unburnt diesel making it's way into the exhaust system.

When I removed the old glow plugs I noticed that cylinder 6 in particular was heavily coated in carbon so I've also arranged for a Terra Clean to hopefully restore some economy and performance. To be honest just renewing the glow plugs and the faulty module has made a big difference to how it runs and idles, its incredibly smooth now. Too early to notice any changes in fuel consumption though.