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harrids
New User
Dec 15, 2011, 10:54 PM
Post #1 of 4
(15471 views)
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Chevy 3.4L high idle
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I've got a 2002 Chevy Impala with a 3.4l engine that is randomly running at high idle. When it started I figured it was a vacuum leak. So I ended up replacing the lower intake gasket with the improved metal gaskets. Also had the heads redone along with making sure the intake surfaces were true. Also cleaned the upper intake some and throttle body before reassembling. Definitively runs smoother now but the high idle issue has returned. Sometime when it goes to high idle I can shut the engine off and restart and it will run at normal rpm. This evening when I got home it was running at high idle and shutting it off and restarting didn't make a difference. The only code I have is for the 02 sensor. I unplugged the one on the exhaust manifold and started the engine. It ran at normal rpm's but I will see what it does in the morning. Any suggestions would be appreciated. Since the heads were resurfaced, valve job done, the lower intake lightly surfaced because the water passages were towed in, the improved metal gaskets along with a GM approved high temp silicon, and all new bolts that were properly torqued so I'm pretty confident it's not a vacuum leak. I'm pretty sure it a electrical/sensor issue especially since sometime shutting it off and immediately restarting it will idle normal. Seems worse the colder it is outside.
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 16, 2011, 4:21 AM
Post #2 of 4
(15432 views)
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Re: Chevy 3.4L high idle
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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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harrids
New User
Dec 16, 2011, 6:47 AM
Post #3 of 4
(15421 views)
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Re: Chevy 3.4L high idle
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Thanks, I'll use some carb spray to double check for vacuum leaks. When putting the engine back together the throttle plate and bore were thoroughly cleaned. Used q tips and carb cleaner to clean the IAC port. Is there any way to test the IAC with a multimeter before replacing it to make sure it's the problem?
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 16, 2011, 9:48 AM
Post #4 of 4
(15414 views)
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Re: Chevy 3.4L high idle
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No, the meter isn't going to tell you if the IAC is getting stuck.
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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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