Why does my car idle low when starting warm?

When I start my 2001 Mazda Protege cold, the engine starts great with an idle of about 2000 rpms and levels off to just under 1000 rpms in a few minutes. However, when I start it warm, it starts great but the rpms fall to about 500-700 for about 3 seconds, and then quickly goes back up to 1000 rpms (where it should be). It tends to sound like it will stall during thish short 3 second period, but it has not done so yet. What might be the problem?

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  • 1 decade ago
    Favorite Answer

    Nahhhhhh nothing really wrong. What is happening is that the computer sensing that it is already warm is adjusting the mixture to idle in those 2 or 3 seconds to bring it to normal. Now if it does ever start to stall doing that then its a simple adjustment of the idle speed to prevent that from occurring again. Hope this helps ya.........

    Source(s): Wrench-Head
  • 1 decade ago

    Thats the known warm up faze! When an engine is cold IT revs up to higher rpm and slowly goes down like yours does. Theres no need for it to idle high when its already warm, it could cause it to over heat specially in the summer time or if you have the a/c blowing. Most vehicles idle around 550 to 750 when warmed up. Your car might only have a few possible problems that could cause this. Mass Air, TPS, air idle control ( if equipped ) ECM ( comp) possibility of dirty injectors. Engine light on? If the engine light isn't coming on its harder to figure out whats going on. But it all sounds fine in my opinion, I think your hearing the engine slow down and it just gets so quite that you think in might stall. But I dont think theres anything wrong.

    Source(s): CERTIFIED MECHANIC
  • Anonymous
    4 years ago

    Yeah, everytime there is an idle difficulty in a vehicle that's going to be the IAC. i could end spectacular now as you're already swapping out factors hoping for a low priced fix. You suitable wager because of the fact it must be one among those great style of issues inflicting that's to take it to a save that makes a speciality of diag paintings. you prefer a save that employs grasp ase qualified technicians and pay the only hour diag fee 40 5-one hundred fifty money based the place you reside.

  • Anonymous
    1 decade ago

    Welcome to the world of smog requirements. To clean up the exhaust at idle, they lean it WAY down.

    Cold idle...They can't help that, you need it to run a bit high to stay running.

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  • 1 decade ago

    its already warmed up.

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