91 ls400 hard to start after sitting overnight?

Hello, The car takes about 10 seconds of cranking to start in the morning? After that it will start up instantly everytime even if it
sits for 4 hours I will come back and it starts in 2 seconds? I was thinking about changing sparkplugs but dont know if its a waste of money? Car runs perfectly otherwise....Thanks:)
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On Sun, 11 Feb 2007 02:57:12 -0500, snipped-for-privacy@webtv.net (:\) :\)) graced this newsgroup with:

it's not the plugs. I'm no expert but it sounds like either an idle air control valve or leaky injectors.
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With the lack of other symptoms, I doubt if there is anything wrong with the engine.
To diagnose the condition, install a fuel pressure gauge at the injector rail, note the fuel pressure there, and park overnight. If fuel pressure gradually decreases, the fuel pressure regulator may be bleeding down. The long cranking time is what it takes for the fuel pump to build up sufficient pressure and volume to start the car.
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Ray O
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On Sun, 11 Feb 2007 10:33:02 -0600, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote:

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The fuel pump only operates if the engine is cranking or running. Turning the ignition switch to the on position without cranking will not energize the fuel pump.
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Ray O
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Ray O wrote:

I thought it energized it for about one second (if you didn't crank immediately).
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I am pretty sure that the fuel pump is only energized if the crankshaft is rotating.
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Ray O
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Hello and Thanks fot all of you for the help. I turned the key to see if I would hear the fuel pump energize but nothing. I had a bmw which when I turned the key it would buzz for a couple of seconds but the lexus doesnt do this. I changed out the plugs today for good measure and will see what it does tomorrow morning. Im still leaning toward the IAC(idle air control valve). When the car is cold and I unplug the iac the idle will rev up and down. When the engine is warm and I unplug it nothing happens besides my car has a low idle when warmed up..should be 600 +/- in park with warm engine..Im at 400 in park with warm engine... The iac is a large contraption at the front of the motor not near the throttlebody. There are coolant lines going into as well. I pulled out the piece that rotates(with 2 bearings on it) and am not sure if this works or not ...but might try to replace the bearings as the iac costs $700 for a new one....would a bad iac cause the hard start in the morning as well??? Thanks again:)
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A bad IAC can cause poor idling but it is not likely to cause long cranking times after a cold soak. You can try cleaning the moving parts of the IAC with throttle body or carb cleaner, and it may improve idling but I would be surprised if it fixes the long cranking times.
If you can rent, borrow, or buy a fuel pressure gauge, you can see if fuel pressure drops overnight. If so, the fuel pressure regulator is bleeding down and the fuel pump has to re-pressurize the fuel lines for the engine to start.
I would not waste time listening to see if you can hear the fuel pump because if the engine does eventually start, the fuel pump is good. If the fuel pump is bad, the car won't start.
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