As soon as the engine is warm, the engine looses power?

CJAMCEKS4

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According to the mechanic the fuel pressure dropped when the engine got warm, the pressure dropped (at least until they replaced the 2nd fuel pump). It's not clear that they have measured the fuel pressure. I think it is something in the fuel control system but not sure what or how to diagnose.

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Sunday, July 3rd, 2011 AT 12:46 PM

RIVERMIKERAT

MECHANIC
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You can borrow a fuel pressure tester from a parts store like Autozone, Pep Boys or O'Reilly. Fuel pressure dropping when the engine gets warm means that part of the fuel is vaporizing in the lines. Vapors compress while liquids don't.
Also make sure the air gap for the crank position sensor is set properly and that it is securely attached.

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Sunday, July 3rd, 2011 AT 7:11 PM

CJAMCEKS4

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I thought vapor lock was not a problem in fuel injected systems. Since the pump is in the fuel tank and the system is pressurized, it seems like it would be very hard to get vapor lock. With vapor lock, once the car starts running rough, it would be impossible to start. That is not the case. The car starts fine even when warm, it just lacks power.

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Monday, July 4th, 2011 AT 1:42 PM

RIVERMIKERAT

MECHANIC
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But the fuel pressure drops once the engine reaches operating temperature, according to your description. Vapor lock isn't as much of an issue in injected vehicles, as long as fuel pressure is maintained. And since the fuel has farther to travel after being pressurized, it has more time to reach the temperature at which vaporization can begin. This is why most fuel pumps pressurize the system to much higher than what injectors can handle, then the pressure regulator releases excess pressure before the fuel reaches the fuel rail and injectors.

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Monday, July 4th, 2011 AT 3:51 PM

CJAMCEKS4

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The mechanic gave up and sent it to Ford. I've read several sites that said it could be the timing belt slipping a notch. The codes came back intermittent low voltage camshaft position sensor and intermittent low voltage crankshaft position sensor. The thing these two things have in common is timing. The timing belt had slipped one notch due to a failed harmonic stabilizer.