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Old 04-13-2010, 08:51 PM   #1
fredfox
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Default will a bad MAF cause high idle?

All of a sudden I am idling at 1300 rpm.
Checked all over for vacuum leaks and found none. I took the maf off and cleaned it lightly with either and it seemed to idle for about 10 seconds then back up?
What else can cause it?
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Old 04-13-2010, 09:53 PM   #2
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The idle stabilizer valve.....it is what sets the idle speed.
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Old 04-13-2010, 10:32 PM   #3
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Is that the valve that is buried under the intake behind the throttle valve on the right side looking from the seat??
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Old 04-14-2010, 09:21 AM   #4
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Yes. It is the valve that's buried. You can unplug it and test it directly with 12v without needing to remove the intake.

Also, bad ground path to the TEMP-II sensor can cause a high idle. Stuck throttle cable. Bad Idle/WOT switch.

Last, how did you test for intake leaks? Smoke machine? I ask, because it is really hard to figure out if the breather hoses under the intake are leaky without a smoke machine.
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Old 04-14-2010, 09:23 AM   #5
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EDIT: On your 86.5 it is way easier to check the ISV than on an S4. Middle pin on the valve is 12v. Apply ground to each outer pin - one at a time - and you should hear the ISV move.

Last, on the S3 motors there is a shorty harness from the idle/wot switch to the main engine harness. It can also be a problem. Most original-equipment shorties are dead by now. The harness is NLA. You have to make a new one from new connectors. Or I think 928sRUs sells a pre-made replacement.
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Old 04-14-2010, 09:55 AM   #6
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Agree with Dave C., probably the harness for the idle/WOT switch. Mine disintegrated as most do. 928sRUs does sell a replacement since it is NLA from Porsche.
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Old 04-14-2010, 11:44 AM   #7
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Quote:
Originally Posted by worf928 View Post
Yes. It is the valve that's buried. You can unplug it and test it directly with 12v without needing to remove the intake.

Also, bad ground path to the TEMP-II sensor can cause a high idle. Stuck throttle cable. Bad Idle/WOT switch.

Last, how did you test for intake leaks? Smoke machine? I ask, because it is really hard to figure out if the breather hoses under the intake are leaky without a smoke machine.
Where is the temp II switch located on these?
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Old 04-14-2010, 08:32 PM   #8
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Ok, I have narrowed it to the isv, how does this valve work? With engine off, key on, I have 0 voltage to the center pin.
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Old 04-14-2010, 08:32 PM
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