Car won't start in the heat

My 1992 Nissan Sentra won’t start when it’s hot outside (after having sat in the heat/sun), but it starts up fine in cooler weather. We’ve replaced filters, plugs, and the starter, but it still won’t start in the heat. Any ideas? Solving this mystery is getting expensive: My husband plans to replace the ignition next. Please email me at:

You haven’t told us what happens when you turn the key.

Instead of throwing an ignition switch at it, I’d throw an ‘inhibitor relay’ at it. It might stick better.