Adjusting idle
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Member
Joined: Jun 2000
Posts: 237
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From: Saskatchewan, Canada
Car: 1986 Z28
Engine: 305
Transmission: 700-R4
Adjusting idle
How do I adjust the idle speed on my '86 Z28 with the 4BBL Quadrajet carb? It has a/c, but I don't have that connected right now. It idles around 1800 right now, and drops to just below 1000 in gear. What do I set it to?
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Take 'er easy, and if
she's easy, take 'er twice!!!
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Take 'er easy, and if
she's easy, take 'er twice!!!
Senior Member
Joined: Dec 2000
Posts: 886
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From: Raleigh, NC, USA
There's a little torx screw that's touching the throttle linkage.. it's near the top of the carb on the driver's side. You may also want to check for vacuum leaks.
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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else
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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else
Moderator
Joined: Jan 2000
Posts: 19,659
Likes: 310
Hum,
One of those vacuum leaks can also be the PCV valve or power brake booster. I've had both happen and it about drove me weird trying to find them, especially the brake booster because the brakes acted completely normally.
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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
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One of those vacuum leaks can also be the PCV valve or power brake booster. I've had both happen and it about drove me weird trying to find them, especially the brake booster because the brakes acted completely normally.
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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
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Joined: Jan 2001
Posts: 254
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From: Bloomington, MN
Same question but only for TBI, after a couple mods some things I did would make my idle go up and others go down. Before she sat at a nice 500, now its about 750-800. Can/should I adjust this and how to. Thanks
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--Spyder--
1992 Camaro RS
LO3, T-56,centerforce clutch, ported and polished heads, Edelbrock Performer Intake, 14X3 Open Element w/ K&N, hiflow cats (and thats it), AC delete, alu drive shaft, 3.73 posi, 170 stat w/ fan switch, STB, Subframe connectors, KYB AGX, Eagle GSC, and poly bushings.
1982 Z-28
Project car, ZZ4 in the works.
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--Spyder--
1992 Camaro RS
LO3, T-56,centerforce clutch, ported and polished heads, Edelbrock Performer Intake, 14X3 Open Element w/ K&N, hiflow cats (and thats it), AC delete, alu drive shaft, 3.73 posi, 170 stat w/ fan switch, STB, Subframe connectors, KYB AGX, Eagle GSC, and poly bushings.
1982 Z-28
Project car, ZZ4 in the works.
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Joined: Jan 2000
Posts: 19,659
Likes: 310
Spyder,
You really can't do too much to adjust the idle speed on a TBI. The ECM has a target idle programmed, and it depends mostly on coolant temperature. If there is something in the system that admits more air than was intended, the ECM will try to maintain mixture ratio but the control over idle speed will suffer. If the IAC is clean and operating properly, and the throttle is closed all the way (with the stop screw backed out fully), you have some other source of air entering the intake.
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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader
You really can't do too much to adjust the idle speed on a TBI. The ECM has a target idle programmed, and it depends mostly on coolant temperature. If there is something in the system that admits more air than was intended, the ECM will try to maintain mixture ratio but the control over idle speed will suffer. If the IAC is clean and operating properly, and the throttle is closed all the way (with the stop screw backed out fully), you have some other source of air entering the intake.
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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader
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