2005 5.0 GXI revs up on cold start

[highpowerdad]

Hello again, so I have a question about how my 2005 5.0 GXI is starting. On the first start of a cold motor, it instantly turns over (starts), but then in about a second, stumbles, almost stalls and then catches itself and revs up to about 2K rpms and then settles down to 600ish rpm idle speed. After that it is fine, restarts "normal" and goes right to idle all day long. Then when starting cold the next day or a few days later, the cycle seems to repeat with start-stumble-rev-up-settle to idle. It has done it for a while now, I have replaced - as part of normal maintenance, cap/rotor/wires and plugs, with no change in the behavior. I am getting ready to change the fuel pump since it is whining pretty loud, but I don't think that is causing this problem, though I am guessing it is starving for fuel - or air, right after startup...
Thanks
Scott

 

[Fun Times]

Hi there, As a test on your next cold engine start up, 'Before "Cranking" the engine over, first try cycling the ignition key to the on position for a few seconds which should allow the fuel pumps to turn on to prime the fuel system up, then repeat the ignition power up cycle one more time again allowing the fuel pressure to continue building up some more pressure internally before you start cranking the engine over to actually start.... See if performing a 2 ignition key on cycle helps solves this any.

 

[highpowerdad]

Hi there, As a test on your next cold engine start up, 'Before "Cranking" the engine over, first try cycling the ignition key to the on position for a few seconds which should allow the fuel pumps to turn on to prime the fuel system up, then repeat the ignition power up cycle one more time again allowing the fuel pressure to continue building up some more pressure internally before you start cranking the engine over to actually start.... See if performing a 2 ignition key on cycle helps solves this any.

Fun Times,

Thanks for the suggestion, however, I already do that for a cold start, somewhere I read that one cycle on the Volvo Penta was not enough so I have always done two for a cold start...

I am thinking I may have a marginal IAC or MAP sensor...

 

[QBhoy]

Hi. Sounds like the IAC is faulty, sticking or both.

 

[Tail_Gunner]

Check your fuel pump pressure at the first cold start, while i am not sure of your fuel pump cell it should pressurize then stop. Have a gauge on it during that process, i would be amazed if you did not see a good blip in pressure...Or a drop to after the first few turns of the engine.

 

[djkoet]

Hello again, so I have a question about how my 2005 5.0 GXI is starting. On the first start of a cold motor, it instantly turns over (starts), but then in about a second, stumbles, almost stalls and then catches itself and revs up to about 2K rpms and then settles down to 600ish rpm idle speed. After that it is fine, restarts "normal" and goes right to idle all day long. Then when starting cold the next day or a few days later, the cycle seems to repeat with start-stumble-rev-up-settle to idle. It has done it for a while now, I have replaced - as part of normal maintenance, cap/rotor/wires and plugs, with no change in the behavior. I am getting ready to change the fuel pump since it is whining pretty loud, but I don't think that is causing this problem, though I am guessing it is starving for fuel - or air, right after startup...
Thanks
Scott

Hello, I'm having the same issue you are describing. Did you ever find the root cause of the start up issue on your 2005 GXI? Thanks for any insight!

 

[highpowerdad]

Hello, I'm having the same issue you are describing. Did you ever find the root cause of the start up issue on your 2005 GXI? Thanks for any insight!

I changed the IAC and cleaned the MAP, but mine only did it in relatively cold weather, so I don’t really know if I got it or not since our cold season last only a couple weeks...I have also read where the temp sensor that is on the thermostat housing that is for the ecm could also cause the same problem if bad, doesn’t tell the ecm that it’s cold and to add gas. Mine seemed to have the right resistance, so I don’t think that was the problem with it.