Hard to start when hot

Hi,

First, if the check engine light stays on when the engine is running, you need to scan the computer for diagnostic trouble codes. This will help focus our diagnosis. Here is a quick video showing how it is done:

https://youtu.be/YV3TRZwer8k

I realize most people don't own a scanner, but often times a parts store will do it free of charge.

Next, what you described sounds like it could be related to a crankshaft position sensor. When they start going bad, heat causes them to fail. Do me a favor, take a look through these links. The first describes the sensor, the second symptoms, and the third explains how in general one is replaced.

https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

If you feel the symptoms indicated in the aforementioned symptoms link mirror what you experience, the best thing to do is this. One, you can check to see if ignition spark is lost when the engine stalls and fails to start:

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Or if you have or have access to a live data scanner, you can check to see if the RPM signal is lost when it fails to start.

If you determine that the sensor is the problem, the sensor is not too hard to replace. Here are the directions specific to your vehicle. The attached pic correlates with the directions.

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2004 Mazda RX8 2RTR-1.3L
Eccentric Shaft Position Sensor
Vehicle Powertrain Management Sensors and Switches - Powertrain Management Sensors and Switches - Computers and Control Systems Crankshaft Position Sensor Service and Repair Procedures Eccentric Shaft Position Sensor
ECCENTRIC SHAFT POSITION SENSOR
ECCENTRIC SHAFT POSITION SENSOR REMOVAL/INSTALLATION

CAUTION: When replacing the eccentric shaft position sensor, make sure there is no foreign material on it such as metal shavings. If it is installed with foreign material, the sensor output signal will malfunction resulting from fluctuation in magnetic flux and cause a deterioration in engine
control.

1. Disconnect the eccentric shaft position sensor connector.

see pic 1ckp

2. Remove the eccentric shaft position sensor installation bolt and remove the eccentric shaft position sensor.
3. Install in the reverse order of removal.

Eccentric shaft position sensor tightening torque: 7.9 - 10.7 N.m 80 - 110 kgf.cm, 69 - 95 in.lbf

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Let me know what you find or if you have other questions.

Take care,
Joe

You are very welcome. If you have the chance, let me know what you find or if you need help with anything.

Take care,
Joe