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Rough idle 1999 Buick Century
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azronin
Novice
Jul 30, 2011, 1:54 PM
Post #1 of 8
(8968 views)
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Rough idle 1999 Buick Century
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My first attempt:
1999
Buick
Century
3.1 Liter
Roughly 165,000 miles
Problem:
Starts okay but idles rough. It will rev up about every 10 seconds then goes back to idling roughly. If I hold the throttle slightly, it seems to idle a little smoother.
Codes:
P0440 Evaporative Emission control system malfunction.
What I've tried:
1) New gas cap - problem remains.
2) Clear code with rented scanner - problem remains.
I purchased a replacement "Purge Valve" and a Haynes manual but I cannot find the part.
Any suggestions?
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 30, 2011, 2:19 PM
Post #2 of 8
(8955 views)
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Re: Rough idle 1999 Buick Century
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The PO440 has nothing to do with the way the engine is running. That is a fuel tank vapor code.
For the engine problem.
You may have a bad IAC ( idle air control) but try eliminating any vacuum leaks and cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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azronin
Novice
Jul 30, 2011, 2:36 PM
Post #3 of 8
(8951 views)
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Re: Rough idle 1999 Buick Century
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I'll try it. Thank you.
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azronin
Novice
Jul 30, 2011, 6:27 PM
Post #4 of 8
(8940 views)
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Re: Rough idle 1999 Buick Century
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Okay, I replaced the Idle Air Control and IT SEEMS TO HAVE CORRECTED THE PROBLEM!
I thank you for getting me on track.
I have one other question:
I didn't clean the throttle body per your instructions. I just replaced the IAC. Is that still required?
I'll do it if you think it's best. I took the short cut because I live in Phoenix and it's about 800 degrees F. Today we've got high humidity so it feels hotter.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 30, 2011, 6:29 PM
Post #5 of 8
(8935 views)
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Re: Rough idle 1999 Buick Century
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I wouldn't have told you to do it if it wasn't important
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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azronin
Novice
Jul 30, 2011, 6:37 PM
Post #6 of 8
(8926 views)
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Re: Rough idle 1999 Buick Century
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Thanks, I'll take care of it now.
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azronin
Novice
Jul 30, 2011, 6:58 PM
Post #7 of 8
(8917 views)
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Re: Rough idle 1999 Buick Century
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Problem solved. Thank you again.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 30, 2011, 7:05 PM
Post #8 of 8
(8913 views)
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Re: Rough idle 1999 Buick Century
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You're welcome
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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