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Audi is tempermental to hot weather

What would you say if I told you that my 2007 Audi A6 does not like it outside when it gets over 80 degrees? Twice now it has refused to start when left out in extreme heat (anything over 85). The first time was during a garage clean out one Saturday. It sat in the driveway for 3 hours in a heat index of about 88-90. After cleaning the garage I went to move it back in. It would not start. We called AAA to tow it on Monday. At dark, I remembered it was still out there and went to lock it. What the heck, I decided to give it another chance. It fired right up. The second time my husband and I were visiting my Son’s future Father-In-Law at the dealership he works at part time. We left the car in the sun from around 10 in the morning until 3 that afternoon. The temperture was around 92. At 3:00 I tried starting it. No, it was hot and refused to start. The dealership even tried to jump start it. We came back to the dealership after dark and it fired right up. He could not believe it. How barzarre is this? Any ideas why this is happening?

Is it cranking, but not starting?

Doesn’t just turning the key make an Audi temperamental?

It is turning over (cranking) but not starting. Its good for a couple of hours, but anything over 4 hours in the heat and it gets its temper up and refuses to start. Complete diagnosis on it today and it does not show anything wrong.

A complete diagnosis of what? Did the mechanic give you a list of things they looked at? If so, post the list and we may be able to see something.

If you are not a fixit yourself guy try stopping at preferred dealer or mechanic when you believe failure is imminent. If it fails to start let them diagnose it in failure mode.

If you don’t know already, get to recognize the sound of the fuel pump running when turning the key to RUN before turning it to START. Then, when it doesn’t start, see if you can hear the pump. If you can’t, some fuel pump relays get temperamental in hot weather.

All good comments above. There’s a dozen or more things that could cause this. I’d suspect – in this order – a crank or cam sensor malfunction, fuel pump or fuel pump relay, or a too-rich fuel mixture problem. Re the latter: Engines need a richer mixture on cold starts, so they have methods to do that, more gas gets injected on cold starts. But it is only supposed to happen if the coolant is cold. On warm days it shouldn’t enrich the mixture, or at least not as much. Maybe something is wrong with all that. That could be a problem with the coolant temp sensor, or a leaking injector, etc