Author Topic: very high idle. fouled plugs. idle mixture screws not responding.  (Read 21117 times)

Offline Irish_Alley

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #30 on: August 07, 2011, 04:18:28 pm »
the real thing to worry about is if it stalls and you dont want it to be to lean
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline txchainsawgogi

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #31 on: August 09, 2011, 11:37:31 am »
After it warms up...it starts idling high AGAIN. It was low two days ago...but when it gets hot...boom 700rpm/1300rpm (drive/park).

Also it dieseled yesterday like its rich but the exhaust is the cleanest looking I've ever seen it.

Offline beastie_3

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #32 on: August 09, 2011, 12:46:31 pm »
dieseling=timing usually.

Offline 1979C20

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #33 on: August 09, 2011, 12:56:53 pm »
dieseling=timing usually.
X2

Advanced too far.
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Offline txchainsawgogi

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #34 on: August 09, 2011, 07:14:39 pm »
oh yeah...got it. This high idle thing has me stumped AND p.o. big time.

Offline txchainsawgogi

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #35 on: August 17, 2011, 11:12:11 pm »
new symptom! its no longer carbon fouling the plugs, now the plugs are showing signs of the mixture being too lean. the idle is (usually) within the ballpark range of where it should be but its a very rough, sluggish idle.

if youre sitting at a stop light it'll noticeably shake and shimmy while the rpms dip around the 550 mark. idle in park is fine. driving conditions are fine.

the other odd thing i noticed is a slight bit of grey smoke on start up that doesnt happen everytime, and is so light that its hard to pinpoint where its coming from. looks like its coming from the under the front of the engine, possibly by the harmonic balancer.

Offline 1979C20

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #36 on: August 18, 2011, 02:45:20 am »
Check the plugs from both sides of the motor, if they are both lean burning, screw each mixture screw in 1/4 turn. Then check pkugs again.
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Offline txchainsawgogi

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #37 on: August 18, 2011, 05:06:46 pm »
 I thought turning it in made it leaner?

Offline 1979C20

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #38 on: August 18, 2011, 06:33:05 pm »
Turn the screws in, gives less air, makes it richer. Turn screws out gives more air, makes it leaner.
1979 SCLB C20 Q-jet 350 SM465 14b F.F. 4.10 G80
1989 GMC Suburban V2500 TBI350 TH400 4in lift 35's 14b SF

Offline Irish_Alley

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #39 on: August 18, 2011, 07:59:26 pm »
http://www.ehow.com/how_7763497_tune-quadrajet.html
love step number 5 but you need to start from scratch
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline txchainsawgogi

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #40 on: August 20, 2011, 12:32:21 pm »
when that person says "plug the tach into the vacuum port on the carb" do they mean a vacuum gauge?

Offline Irish_Alley

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Re: very high idle. fouled plugs. idle mixture screws not responding.
« Reply #41 on: August 20, 2011, 08:47:23 pm »
I hope so lol
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes