Hello. I have a 2007 murano sl... 72k... when I first start it in the morning it has a hard time turning over for a few seconds and then once it does, the rpms shoot way up then back down to normal almost like I'm flooring the gas pedal but I'm not touching it at all.. it only does this on the first start of the day. I can start it after that and its fine... any ideas on where to start? we did just replace both cam shaft sensors... maybe that might have something to do with it?
racoyodi
This sounds like the fuel pressure is dropping down after being off for several hours. A fuel injection system should be able to hold the fuel pressure up for several days. Without full fuel pressure at startup, the engine will crank until it detects proper cylinder firing. The computer will tend to over rev the engine for a few seconds when this happens.
To test, a garage will install an inline fuel pressure gauge and observe it over time to see if the pressure drops. If it drops over 6 hours, it's a sign that your fuel pump is having trouble holding the pressure when the engine is off and it should be replaced.
Some vehicles also employ an inline valve after the fuel pump to hold the fuel pressure. I don't believe Nissan uses one, relying on the fuel pump to hold fuel pressure.
Hope this points you in the right direction.
Have a good day.
To test, a garage will install an inline fuel pressure gauge and observe it over time to see if the pressure drops. If it drops over 6 hours, it's a sign that your fuel pump is having trouble holding the pressure when the engine is off and it should be replaced.
Some vehicles also employ an inline valve after the fuel pump to hold the fuel pressure. I don't believe Nissan uses one, relying on the fuel pump to hold fuel pressure.
Hope this points you in the right direction.
Have a good day.
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