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Seville STS 2001, Eldorado 1997
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394 Posts
Discussion Starter #1
About a week ago, the car would start, then RPM would fall and car would stall. I removed IAC motor and throttle body and cleaned very well with throttle body cleaner. I used just cloth with the spray. I removed the rubber channel up till TB (where the TB flapper becomes visible). After I cleaned, car worked fine. Today again got same problem when car will die immediately after starting (RPM falls). Again cleaned TB and IAC this time with TB cleaner spray and used toothbrush and cloth. Car is starting but RPM is about 500 and getting code P0506 Cadillac - Idle Speed Control System RPM Lower Than Expected

I did not remove TB. I was quite sure that I cleaned very well. Any ideas what to check. Could there be any vacuum leak. I checked physically and could not notice any vacuum pipe leaks. Any ideas please

Thanks
John
 

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White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Re: Low RPM, P0506 Cadillac STS 2001

Did you spray TB cleaner through the IAC passages?
Other than that, all I can think of is maybe a failing IAC valve.
 

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2001 STS
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71 Posts
Re: Low RPM, P0506 Cadillac STS 2001

I had the same trouble with my 2001 STS, kept stalling unless I kept my foot on the accelerator. I replaced my IAC and no problem. It was the easiest part I had to replace.

2001STSCADDY
 

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Seville STS 2001, Eldorado 1997
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394 Posts
Discussion Starter #4
Thank you Ranger and 2001STSCADDY. I sprayed TB cleaner in IAC path and put my finger with cloth and cleaned very well. I think that it is bad IAC part. I am going to replace it and share outcome.
Thanks
John
 

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2002 STS, 2005 CTS 3.6
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413 Posts
Did you take the IAC apart? Easy fix, save your money for something else! Remove the IAC and (twist out) the plunger and spring, clean everything good, it will likely have crud in there. Then screw it back in all the way tight. Reinstall, fire it up and drive around a bit and clear your codes. This normally cures the idle problems relating to those DTC codes as the plunger tends to turn out over time and block the idle air holes in the throttle body.
 

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Seville STS 2001, Eldorado 1997
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394 Posts
Discussion Starter #6
I replaced IAC valve. Problem resolved. I bought new one for less than $10 from ebay. Thank you all for your feedback.

Thanks
Anwer
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
Less than ten dollars?? I hope it was a used AC Delco, and not no name garbage.
 
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