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2001 DHS
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Discussion Starter #1
Last few days my car RPM randomly goes up and either stays up or gradually comes down. This happens around 50% of the time during the day and not always. Today finally it set a code:

P0507 - Idle Air Control System RPM Higher than expected.

The TB was last cleaned about 2-3 months and is something I always keep clean routinely. I know a Vacuum leak could also cause this, my question is if it's a Vac leak would it always idle high or it's possible for it to run normal at times and high at other times? Any suggestions as to where to start and where to end to? Thanks
 

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White Diamond '03 DHS (with DTS floor shift)
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Re: P0507 - Idle Air Control System RPM Higher than expected.

Since you have an IAC related code, I'd suspect the IAC, not a vacuum leak.
 

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2001 DHS
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Discussion Starter #3
Re: P0507 - Idle Air Control System RPM Higher than expected.

Thanks ranger. Would you happen to know what parts I would need and whether it's OK to use non-AC Delco?
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
You'd need the IAC valve, the O ring comes on it.

AC Delco only. If you don't want to spend that much, get a used AC Delco before buying a new aftermarket part.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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I'd be very suspicious of that being genuine AC Delco if it is in fact new (as per the ad). That's a $187 part on Rockauto.

That is the correct part number though.
 

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2001 DHS
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Discussion Starter #8
Re: P0507 - Idle Air Control System RPM Higher than expected.

From you all's experience, do you think cleaning the IAC (as it's never been cleaned before) should resolve the issue or I should replace it ?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Re: P0507 - Idle Air Control System RPM Higher than expected.

If the IAC top hat (plunger) and the TB bore internal passages have never been cleaned carefully with TB spray and lint free rags and fuzzy pipe cleaners from a craft store, then it's entirely possible that the PCM is overcorrecting for idle speeds due to inaccurate bypass airflow - the IAC is the "Idle Air Control" - same theory as the idle stop screw on a carburetor.

You carefully remove the electrical connector, remove the two Philips or Torx screws, pull the IAC straight out and clean the top hat and throttlebody bore. Don't try to push the top hat (plunger) in and out, and don't get TB cleaner spray up the operating shaft.

After reassembly, perform a TPS and IAC relearn procedure: TPS - Turn the Key: ON for 30 seconds, turn it OFF for 1 minute. IAC - Start the engine and let it complete the fast idle stepdown sequence, turn it off for at least 30 seconds. (GM service manual, Fuel/Air, IAC service chapter)

Always attempt normal maintenance before throwing parts at it.
 

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2003 Deville Base
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Re: P0507 - Idle Air Control System RPM Higher than expected.

Thanks Moist, I found this part on eBay http://www.ebay.com/itm/161587058180?item=161587058180&viewitem=&sspagename=ADME:X:AAQ:MOTORS:1123&vxp=mtr , it's surprisingly low in price, is that the correct part I would need?
I have bought items from that eBay seller and they were not as advertised. On the upside, the accepted they return and credited my PayPal account. If a price is too good to be true...
 

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White Diamond '03 DHS (with DTS floor shift)
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Re: P0507 - Idle Air Control System RPM Higher than expected.

From you all's experience, do you think cleaning the IAC (as it's never been cleaned before) should resolve the issue or I should replace it ?
TB's need cleaning. IAC valves rarely do. They get a little sooty, but that's about it. That said, it will take about :15 min. to pull it and wipe it down. Can't hurt to try that first.
 

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2001 DHS
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Discussion Starter #12
Re: P0507 - Idle Air Control System RPM Higher than expected.

Always attempt normal maintenance before throwing parts at it.
Hi Sub, is there anywhere I can get the full re-learn procedure from? Perhaps you would know of any links?
 

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1996 Deville Concours
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Also, if you clean the TB often, make double sure that you didn't put the gasket on backwards. It's close enough to symmetrical to be possible. Someone suggested that to me on here when I had that code and it turned out...uh...I mean I heard that...a friend of mine said that he had that happen once....:-D
 

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2001 DHS
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Discussion Starter #15
The TB has never been removed for cleaning. I just spray it holding the throttle plate open and reaching in with a rag and around the plate. Is that sufficient ?
 

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White Diamond '03 DHS (with DTS floor shift)
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Yes, as long as it comes out clean. Sometimes you may need a toothbrush if it hasn't been done in many years.
 

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2001 DHS
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Discussion Starter #17
CONCLUSION: I went ahead and cleaned the IAC (TB was very clean) and everything looks great. So far after driving 3 days the RPM is where it should be at all times. Thank you all
 

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2001 DHS
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Discussion Starter #18
Not sure if I've become disillusion but the car hauls ass. It's become so much quicker and more responsive to the pedal, could that IAC really make this much of a difference in performance?
 

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2001 DHS
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Discussion Starter #20
UPDATE: The IAC cleaning lasted only 10 days, Error came back up today. I think it's time to change the IAC out
 
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