Odd Recurring Fault

[mobblers]

I have a 2007 saloon that's done 40K miles. About six months ago the car developed a fault that results in the engine management light coming on when I drive for longer than about 30 minutes on the motorway. The light stays on but goes out after about 4 or 5 days of normal driving (short journeys of around 15 minutes). The car has been looked at by Audi 3 times. The first time they told me they replaced a blocked fuel filter and cleaned the throttle body, the second time they told me one of the flaps on an exhaust back box was seized so they replaced the back box and the last time (earlier this week) they told me they couldn't find any fault (no fault codes had been stored in the memory apparently). They said they did a test drive but weren't able to replicate the fault.

I collected the car and agreed with them that I would see if I could get the light to come on and, if I could, I would take the car back while the light was still on and they would run another diagnostic.

Does anyone have any idea what the problem might be and why no error codes would have been stored after the last time it happened? For what it's worth, the first time the car was looked at I was told there were 'system rich faults'. I don't know if the same faults are showing each time this has happened.

As far as I am aware the car is stock without a re-map or any other engine modification.

Thanks in advance for any suggestions.

[R1RS4]

Hi there,

Get yourself a Ross tech vcd's kit,

You can then run a diagnostics check for yourself and share on here and with the wealth of expertise someone will have the answer, kits about £180 ish

But as you know you will save this in visits to the stealers

There are so many things that could bring on the mil light it would be silly to guess, does not say your location, so you could meet up with someone and they could run the test once you have the light on