Our 2014 Allroad won't start sometimes. It's not the battery, starter or alternator. All of that is good. Engine cranks quite quickly when starter engaged, just sometimes the engine won't actually start. Maintained by local Audi dealer. Recent maintenance includes new ignition modules and spark plugs, cleaning the carbon off the valves, etc. Runs perfectly once it starts. We have left the car with the dealer for over a week and they can't find the problem. They say they cranked it several times per day each day and it always started for them on the first time. They can find nothing wrong with the car. There are no codes displayed.

This is my wife's daily driver and she's always concerned that the car may not start for her and she may get stranded somewhere. So far, it has always started, eventually, sometimes after several tries. Sometimes it will go weeks with no problems. Other times it can happen multiple times per day.

Any ideas?