2003 Acura TL has trouble starting when temp is 50 degrees or higher

My 2003 Acura TL has trouble starting if I am running errands and the car is turned off and then I turn it back on. This only occurs when the air temp is 50 degrees. I have had the local Acura dealer evaluate it without a confirmed diagnosis. Help!

What needs to be defined before even making a wild guess is what is meant by trouble starting.

Starter motor cranks engine over but it won’t run?

Stone silence when the key is turned to the START position?

Slight click when the key is turned to START?

Automatic transmission?

Thanks…starter motor cranks but engine won’t turn over. And, once I get the engine to start, it starts hard and runs very rough. Once I get it started however and it passes the sputtering/shaking, it runs like a champ and does not stall.

Have someone check for vapor lock. Vapor lock occurs when the gas boils in the fuel rails when the engine is turned off when hot.

A quick way to check for this is to do a residual fuel pressure test. If the fuel pressure reads normal then quickly drops back down to zero, this can cause the fuel to boil in the fuel rails causing vapor lock.

This would explain the hard starting and the rough running.

Tester