IAC Valve Cleaning
Thread Starter
Instructor
Joined: Apr 2006
Posts: 117
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From: east haven ct.
IAC Valve Cleaning
Hello, I have a 1991 L98 the idle still doesn't seem right, I took the Iac off tonight and cleaned it full of carbon.A mechanic at work suggested that I clean the Iac.Also pushed the pintle within the 11/8 inches.Has anyone done that and the idle seemed to be better? Also the gasket broke if I can't buy the gasket can I make my own with the RIGHT STUFF.Any other ideas for the idle,I did a major tune-up plugs,wires,cap,rotor,fuel,air filters egr valve VETTE mechanic found bad brake booster and vacuum which got me passed on my emission test everything seemed ok, but at lights and stop signs just seems something not right THANKS.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
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From: Louisiana
Yes, cleaning a dirty IAC will make it idle better. This is how I would do it. Turn ignition on, ground terminal A and B of ALDL. Wait 1 minute and disconnect IAC connector, remove ground to ALDL, turn ignition off. I would suggest removing the TB and IAC at the same time and cleaning both. There are air passages that are hard to see with the TB connected to the plenum. I would clean it good with TB cleaner and a toothbrush.
You will need a gasket for the IAC and not just RTV. You can make one from gasket maker (Autozone sells it) or maybe a Chevy dealer can get one, but not likey. I bought a new IAC when my gasket broke so I could have a new gasket. When you install the IAC into the TB, make sure the tip of the pintle is no further than 1 1/8" from the flange of the IAC. You might damage it if not done properly. When TB is mounted back on the plenum (use a new TB gasket) connect all hoses and vacuums and IAC connector. When you start engine notice how it runs (may take a minute to settle). Check for any vacuum leaks as this will make it idle like crap. All IMO
You will need a gasket for the IAC and not just RTV. You can make one from gasket maker (Autozone sells it) or maybe a Chevy dealer can get one, but not likey. I bought a new IAC when my gasket broke so I could have a new gasket. When you install the IAC into the TB, make sure the tip of the pintle is no further than 1 1/8" from the flange of the IAC. You might damage it if not done properly. When TB is mounted back on the plenum (use a new TB gasket) connect all hoses and vacuums and IAC connector. When you start engine notice how it runs (may take a minute to settle). Check for any vacuum leaks as this will make it idle like crap. All IMO
Le Mans Master
Joined: Jun 2005
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From: Texas
Originally Posted by RRT vette
Yes, cleaning a dirty IAC will make it idle better. This is how I would do it. Turn ignition on, ground terminal A and B of ALDL. Wait 1 minute and disconnect IAC connector, remove ground to ALDL, turn ignition off.
Reset IAC valve pintle position:
a) Depress accelerator pedal slightly
b) Start end run engine for five seconds
c) Turn ignition "OFF" for ten seconds
d) Restart engine and check for proper idle operation
Check out Vader86's website (a forum member), its a great place for info on this and other projects.
Team Owner
Joined: Oct 2000
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From: Fort Knox, KY
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For your IAC gasket, you can buy a sheet of gasket paper from an auto parts store and make your own like I did. Put a drop of motor oil on the gasket before bolting it back in to ensure a tight seal.
Cleaning the IAC and TB (throttle body) really mellows out your base idle and improves throttle response and fuel economy, too.
Cleaning the IAC and TB (throttle body) really mellows out your base idle and improves throttle response and fuel economy, too.
Thread Starter
Instructor
Joined: Apr 2006
Posts: 117
Likes: 1
From: east haven ct.
IAC Valve Cleaning
Thanks for the replys.I brought home a sheet of gasket paper from the mechanic at work and will make my own gasket.when I did the intake gaskets last august I cleaned everything up real good but didn't know to clean the IAC.I retracted the pintle all way in hope I didn't screw it up gonna put the TB back in tonite see what happens.Changed all TB gaskets in august. TB to Plenum gasket seems untouched so i'm gonna reuse.Any procedures on TPS adjustment could that be an idling issue also, didn't know about the IAC/TPS issues back in august rookie mechanic but learning fast. THANKS AGAIN.
