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Very High Idle 2100rpm

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Hey Guys,

I really need your help on this one....sadly, this is my first post (not the first post I wanted!). I spent about an hour searching through the various Boxster forums but couldn't find anything similar to the problem I'm having.

I have a 1998 Boxster w/ ~137,000 miles. Manual Transmission.

I spent a few hours today replacing my trans/diff oil and then diagnosing the intermittent P0410/P1411 CEL that I've had since purchasing the car. In diagnosing the CEL, I followed the steps that Loren posted about diagnosing Secondary Air Injection problems. After using Durametric to activate the air injection pump (and confirmed that it is, in fact, working), I started the engine and disconnected the vacuum line connecting to the air change over valve to check for the presence of vacuum (there was). In starting the engine to check for vacuum, the engine idle inexplicably went to 2100rpm (not fluctuating). Even after reconnecting the vacuum line to the change over valve, the idle remains at 2100rpm. I've checked the throttle cable to make sure that it isn't hung up on anything (it isn't) and I unplugged the battery to reset to DME (just in case). Even after restarting the car 4 times now, the idle issue remains. When I was activating the air pump using Durametric, I accidentally clicked on "Start" for IACV and then clicked on "Stop" even though no noise was made. Could that have been part of the problem? I'm at a loss!

Any help would be much appreciated!


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It sounds like your Idle Air Control Valve is hanging up.

Remove it from the throttle body and clean it thoroughly. You will be surprised at how much gunk gets baked in there.

Be careful with the tiny little gasket if you don't have a replacement gasket.

Here's a link to a DIY on how to clean the throttle body, which includes nice pics and instructions on cleaning the IACV: http://pedrosgarage.com/Site_3/Clean_the_Throttle_Body.html

Regards, Maurice.

Edited by 1schoir
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Take a look at the photo in the Throttle Body DIY I linked to above. The IACV is located immediately to the right of the number "3" in the photo.

Go down a little further in the DIY and you'll see exactly what it looks like.

Regards, Maurice..

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