Hard start when engine warm

Hi and thanks for using 2CarPros.

If it only happens when the engine is warm, it could be a few things. First, I will assume the engine isn't overheating. With that, often times it is related to fuel pressure. When the engine is warm, fuel is more likely to vaporize. However, if fuel pressure is maintained, that doesn't happen. With that in mind, the vehicle may have a problem with fuel pressure drop off. Things such as a leaking injector, a one way valve is allowing pressure to drain back to the tank, a very small leak in the system and the list goes on.

With that in mind, you really should check fuel pressure, specifically pressure drop off. Here is a link that shows how this is done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Here are the directions specific to your vehicle. The attached pictures correlate with these directions.

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COMPONENT TESTS AND GENERAL DIAGNOSTICS
FUEL PRESSURE TEST

CAUTION: Safety glasses must be worn when performing this service.

1. Reduce the internal pressure of the fuel pipes and hoses by the following procedures.

Picture 1
- Disconnect the fuel pump harness connector after removing the rear seat cushion.
- Start the engine and after it stalls, turn the ignition switch to the OFF position.
- Disconnect the battery negative (-) terminal
- Connect the fuel pump harness connector

2. The fuel filter is located in the left side of the rear quarter of the engine compartment.
3. Remove the single tie-wrap that secures the fuel pressure line to the fuel return line.

Picture 2
4. Remove the electrical connector from the master cylinder reservoir.

CAUTION: Before proceeding to next step, place shop rag over fuel filter to capture fuel spray.

5. Move shop rag enough to expose bolt on top of fuel filter, remove bolt and line from filter.

Picture 3

6. Using the fuel pressure gauge, gauge connector & gauge adapter (09353-24000, 29000), install the fuel-pressure gauge to the fuel filter. Tighten the bolt to the specified torque.

Fuel pressure gauge to filter torque: 25-35 Nm (18-26 ft.lbs.)

7. Connect the battery negative (-) terminal.
8. Start engine and check for leaks. If no leaks are present, continue with fuel pressure test. (at curb idle speed).

Picture 4
9. Connect (Disconnected) the vacuum hose from the pressure regulator, (and plug the hose end). Measure the fuel pressure

Standard value
Disconnected hose: 300 kPa (44.37 psi)
Connected hose: Approx. 255 kPa (37 psi)

Picture 5
10. If the results of the measurements made in steps 9) are not within the standard value, use the table to determine the probable cause, and make the necessary repairs.

Picture 6

11. Stop the engine and check for a change in the fuel pressure gauge reading, which should hold for approximately 5 minutes. If the gauge indication drops, observe the rate of drop. Determine and remove the causes according to the table.
12. Reduce the pressure in the fuel line.
13. Disconnect the hose and the gauge.

CAUTION: Cover the hose connection with a shop towel to prevent splashing of fuel caused by fuel residual pressure in the fuel line.

14. Replace the O-ring of the end of the hose.
15. Connect the fuel hose to the delivery pipe and tighten with the specified torque.
16. Check for fuel leakage.

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Please keep in mind, if the check engine light is staying on while the engine is running, you should first scan the computer to retrieve diagnostic trouble codes. Here is a quick video showing how it is done:

https://youtu.be/b2IJGfImVvw

I realize most people don't own a scanner. However, if the light stays on, it needs done. If you don't have one, most parts stores will do it for free. Have it done and let me know the codes they find.

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Another issue that create problems when the engine is hot, is the crankshaft position sensor. When the sensors begin to wear out, they become sensitive to heat causing a signal loss. Take a look through these links that discuss the sensor, its purpose, and symptoms of a bad one.

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

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Let me know if any of this helps or if you have questions.

Take care,
Joe