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PRETENDING - Overheating but not overheated

HELP My Mazda tribute 2003 (manual) has developed a habit of ‘pretending’ to be overheated. If I do more than 2 or 3 stops as I run Saturday errands on a warm day - the care refuses to start and’ continue’ to run. I can start the car but have to rev the engine and restart at every stop sign and red light- If I pop the hood and wait about 40 minutes the car seems to ‘cool’ down and will run. The engine does not redline - water and coolant are fine - Is this just a faulty thermostate or is it some insidious vapor lock- Help

It may be an insideous heat-sensitive ignition component. Or perhaps even a flakey idle air control motor (which DOES have widings and CAN become heat sensitive).
Have you considered having a shop look at it?

Oh, and by the way, how many miles do you have on it?
Have you been keeping up with the tuneuups and scheduled maintenance?
When was the last time the sparkplugs and ignition components (if you have a distributor based system) been changed?

One point: because overhetaing can cause stalling does not mean that stalling is a sign of overheating. You probably do not have a cooling problem. At least not based on your symptoms.

It could be vapor lock.

To find out, carry a bottle of water in the vehicle. The next time the engine refuses to start when hot, pour the water over the fuel rails to cool them down and then try starting the engine. If the engine starts it’s vapor lock.

Now some will tell you that vapor lock can’t occur on a fuel injected engine. But it can. And here’s how. When you shut the engine off the fuel system should hold what is called residual fuel pressure. This means the fuel pressure slowly bleeds down over time after shutting the engine off. If however there is no residual fuel pressure after shutting the engine off and the pressure goes immediatly to zero, this is like a carburated fuel system where heat boils the fuel in the fuel line or in this case the fuel rails and you get vapor lock.

The cause for the fuel system not to hold residual fuel pressure after shutting the engine is shut off is a defective anti-drain back valve in the fuel pump assembly.

Tester

It could be a temperature sensor. Not sure on Mazdas but some other cars have one for the dash and one the ECM uses. If the ECM is seeing the wrong temperature, it will often not start or run like junk.