Project Free Mazda: Erratic idle when cold ?

"Luc - The Acadian Oppo" (luc5) 09/01/2014 at 17:59 • Filed to: PROJECT FREE MAZDA

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Alrighty lets get right to this. !!!error: Indecipherable SUB-paragraph formatting!!! begins. One of the only known issues with the car(other than needing to replace the leaking valve cover gasket) is that the car has pretty erratic idle when cold, the idle surges from 800rpm to 2500rpm constantly.

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The second the car warms up it runs perfectly fine but it can be a little annoying for the neighbors while warming up. It's like the car does not want to "choke" properly. Any ideas what it could be? I'm thinking it has to to with the Idle Air Control Valve. I'll take the valve apart and give it a good cleaning and see what happens. Unless you have a better idea?

They have been running the car like this for years with no issues even their mechanic said that if you can live with the weird idle when cold there is no need to fix it as it won't damage anything. But I like my stuff to run like it was supposed to so I want to take care of the problem.

davedave1111 > Luc - The Acadian Oppo 09/01/2014 at 18:04

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Vacuum leak?

DoYouEvenShift > Luc - The Acadian Oppo 09/01/2014 at 18:04

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Maybe a vacuum leak. Once the o2 sensors warm up, and the car goes into closed loop. The fuel trim corrects for it.

Luc - The Acadian Oppo > DoYouEvenShift 09/01/2014 at 18:07

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You know what that would make perfect sense. what's the best way to test for a vacuum leak? or would if be just as easy to replace all the lines and not have to worry about it again?

Luc - The Acadian Oppo > davedave1111 09/01/2014 at 18:08

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Could be? I can't believe I didn't think of that earlier. I've been driving new cars with warranty for the last 8 years that I'm forgetting how to fix them.

DoYouEvenShift > Luc - The Acadian Oppo 09/01/2014 at 18:28

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Easy way is to grab a bottle of cheap starter fluid from the parts store. With the car running, spray around the intake manifold, vacuum hoses, intake duct, etc. Youll notice the idle change when you hit a leak.

Luc - The Acadian Oppo > DoYouEvenShift 09/01/2014 at 18:30

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good to know. thanks for the help

DoYouEvenShift > Luc - The Acadian Oppo 09/01/2014 at 18:31

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no prob

davedave1111 > Luc - The Acadian Oppo 09/01/2014 at 18:32

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Heh, if it's that my Oppo remote diagnostics 100% run will continue to extend to utterly improbable lengths. Although about 90% of those have been 'bad earth', so maybe I should add that as a backup guess ;)