Q: Rough Idle when first started or when wet

asked by on December 16, 2016

I am having a problem where when i first start the car and the motor bogs down and shakes the whole car and idles at 100 rpms for a minute then revs itself up to 2500 rpms, goes back to about 900 rpms for a few seconds then does the same thing again goes back down to 100 rpms etc, and it does this when wet as well, once the car is warmed up it doesnt do it and it idles at about 850 to 900 rpms which i deem normal and idles fine, unless the car does get wet then it does it unless i floor it and then stop, to which it then stops, any help, or suggenstions on what this is, im thinking its the iac, and the egr valve was already replaced along with plugs and wires

My car has 182000 miles.
My car has an automatic transmission.

Hello, I sounds like you may have a dirty or faulty idle air control valve. As you know, this monitors and reads the air intake as it enters the engine prior to being mixed with fuel while making adjustments to create the proper air/fuel ratio to be injected into the motor. Occasionally, these valves may become faulty when they are dirty, clogged or have the incorrect voltage going to them, which may cause the motor to hunt for the perfect idle as it receives these incorrect readings causing your RPM’s to fluctuate as you describe. I would suggest having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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