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#1 |
Registered User
Join Date: Apr 2006
Location: Katy, Texas 77450
Posts: 31
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High Idle
I am having issues with my 71 with a 350 and q-jet. When I frist start it revs to 2700rpm and stays there for atleast 5-10 min. If I drive it for a while it will finally idle normally. My temperature gauge does not currently work, so really don't know when it is at operating temp. Is there a way to bypass the "choke", and would I want to do this?
Last edited by TexanC3; 10-27-2007 at 08:45 AM. |
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#2 |
Truck Enthusiast
Join Date: Dec 2006
Location: Arlington, WA
Posts: 1,346
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Re: High Idle
is it an electric choke? disconnect the hot wire and remove the choke plate
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'85 swb |
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#3 |
All stock and staying that way
![]() Join Date: Jul 2003
Location: Elkland, PA
Posts: 1,485
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The problem you have is very simple to correct. On the passengers side of the carb on the bottom, there is a fast idle screw. It is attached to the throttle shaft. When the engine is warmed up, the fast idle engine speed should be set for 1800 rpm in park. It sounds like the choke is operating normally, just that someone overdid the fast idle speed.
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1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... ![]() 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... ![]() 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels |
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#4 |
Senior Member
![]() Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,873
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Re: High Idle
Yes , and after a few minutes stab the peddle once and it will come back down.
BTW,the factory service manual for 1969 shows the "fast idle" for a 350 with Q-jet to be 2400 RPM.Maybe it's lower for 1971 as mentioned above.
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. Last edited by WorkinLonghorn; 10-27-2007 at 09:19 AM. |
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#5 |
Registered User
Join Date: Apr 2006
Location: Katy, Texas 77450
Posts: 31
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Re: High Idle
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#6 |
Registered User
Join Date: Apr 2006
Location: Katy, Texas 77450
Posts: 31
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Re: High Idle
I found this website that has info..http://www.jetchip.com/carbtechinfo.asp
"Fast idle screw adjustment: The fast idle screw adjusts the idle speed when the vehicle is cold started and the choke is on. Use a flat head screwdriver to adjust the fast idle speed screw shown in photo. Turn the screw clockwise for a higher idle speed, counter clockwise for a lower idle speed." ![]() |
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#7 | |
Senior Member
![]() Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,873
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Re: High Idle
Quote:
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. Last edited by WorkinLonghorn; 10-27-2007 at 09:43 AM. |
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#8 |
Registered User
Join Date: Jan 2004
Location: Whitehorse YK Canada
Posts: 2,651
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Re: High Idle
I adjusted mine just last week and it sure does run better when cold.
I also found that my choke linkage had 15 years of dirt and gunk on it and was sticking. So I sprayed down the choke linkage with penetrating oil to clean it up. That helped as well. So without a tach in the truck how can I tell the rpm of the engine?
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Blaine 59 GMC 9314 a.k.a. Whoopee 68 C20 50th Anniversary a.k.a. The Rat http://www.flickr.com/photos/northerngmc/ http://www.members.tripod.com/P-wee/index_032.htm 1.61803 is one H of a lot better than 3.14159, no really it is! |
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#9 |
Active Member
![]() Join Date: Jul 2007
Location: Centrally located between Houston, Austin and Waco. BCS area.
Posts: 7,947
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Re: High Idle
So without a tach in the truck how can I tell the rpm of the engine?
This is similar to what I have to check mine... http://www.amazon.com/Actron-CP7605-...3331942&sr=8-2 Last edited by 68gmsee; 10-27-2007 at 01:15 PM. |
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#10 |
Registered User
Join Date: Jan 2004
Location: Whitehorse YK Canada
Posts: 2,651
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Re: High Idle
Thanks.
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Blaine 59 GMC 9314 a.k.a. Whoopee 68 C20 50th Anniversary a.k.a. The Rat http://www.flickr.com/photos/northerngmc/ http://www.members.tripod.com/P-wee/index_032.htm 1.61803 is one H of a lot better than 3.14159, no really it is! |
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