High idle speed - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tx71smallblock · 01-30-2008, 10:25 AM

My truck is running fine but it idels almost at 1200 rpm. the electric choke is not hooked up and the timing is almost at 18* btdc. whats going on?
really need some help with this
thanks ahead of time
cody

dadsbrew · 01-30-2008, 11:40 AM

check for vacuum leaks, either around the base of the carb or any vacuum lines, possibly internal vacuum leak in the carb. 18 degree's is advanced alot is the advance still hooked up when your setting the timing.

cruiserman · 01-30-2008, 12:58 PM

Turn down the idle speed?

Shyguy · 01-30-2008, 01:51 PM

I had a similar problem and fixed it by putting on a heavier return spring.

Danny

dadsbrew · 01-30-2008, 02:05 PM

yes, I would definetly return the throttle by hand to see if it can come back farther, if it does use a heavier spring, good idea shyguy

tx71smallblock · 02-01-2008, 08:30 AM

Has after market heavy spring, brand new carb, idel screw is backed all the way out

haysonj · 02-01-2008, 11:52 AM

Your secondaries are partially open could be bent rod or just dirty or out of adjustment try to manually close them or look down in the carb to see if one of the screws has come off the butterflies. You should also check the choke cam to make sure it is not holding the throttle open

Kager67 · 02-01-2008, 12:40 PM

Something you could try is to hook up the choke and turn the choke housing a quarter turn counterclockwise (lean). This should make sure the choke isn't part of the problem. My 72 did the same thing and this fixed it.

Kage

68gmsee · 02-01-2008, 12:59 PM

Quote:

Originally Posted by tx71smallblock

Has after market heavy spring, brand new carb, idel screw is backed all the way out

Has it run normal before or is this problem since the carb install?

I would remove the carb and check to make sure that butterfly closes almost shut when at rest. Should have just a small clearance.

If all the mechanicals check out, then possible vacuum leak. Don't overlook cracked hoses or possible transmission modulator if auto.

tx71smallblock · 02-05-2008, 10:56 AM

ok fixed the high idel, the choke cam was holding the throttle open. but now i have a timing question, is the listed 8* btdc before or after you hook up the vacuum advance back up? should i be ideling at 8 with everything buttoned up? or ideling at 8 with the vacuum pluged and then it jump to 10 or 12 with it connected?

cruiserman · 02-05-2008, 12:41 PM

8* base timing, so with vac advance disabled.

tx71smallblock · 02-06-2008, 09:46 AM

thanks cruiserman, is that what most of you are running? with what i put on it should i run somthing different?

01-30-2008, 10:25 AM	#1
tx71smallblock Registered User Join Date: Jun 2007 Location: Georgetown , TX Posts: 166	High idle speed My truck is running fine but it idels almost at 1200 rpm. the electric choke is not hooked up and the timing is almost at 18* btdc. whats going on? really need some help with this thanks ahead of time cody __________________ 70 Chevy C-10 short step 250/3 on the tree Owned: 71 longbed Cheyenne 70 swb

01-30-2008, 11:40 AM	#2
dadsbrew Registered User Join Date: Jan 2008 Location: Federal Way, WA Posts: 53	Re: High idel speed check for vacuum leaks, either around the base of the carb or any vacuum lines, possibly internal vacuum leak in the carb. 18 degree's is advanced alot is the advance still hooked up when your setting the timing. __________________ 1970 K-10 400CID, to much cam--not enough compression Stan's Headers and a 4" lift / 1990 R1500 Suburban 4X4, 350CID with vortec heads, edlebrock intake, TBI, 10:1 compression and Stan's Headers "The probability of someone watching you is directly proportional to the stupidity of your actions"

01-30-2008, 12:58 PM	#3
cruiserman Registered User Join Date: Dec 2006 Location: Idaho Posts: 210	Re: High idel speed Turn down the idle speed? __________________ 72 C2500 LWB 402 Sierra Grande 05 Odyssey 08 Tundra

01-30-2008, 01:51 PM	#4
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: High idel speed I had a similar problem and fixed it by putting on a heavier return spring. Danny

01-30-2008, 02:05 PM	#5
dadsbrew Registered User Join Date: Jan 2008 Location: Federal Way, WA Posts: 53	Re: High idle speed yes, I would definetly return the throttle by hand to see if it can come back farther, if it does use a heavier spring, good idea shyguy __________________ 1970 K-10 400CID, to much cam--not enough compression Stan's Headers and a 4" lift / 1990 R1500 Suburban 4X4, 350CID with vortec heads, edlebrock intake, TBI, 10:1 compression and Stan's Headers "The probability of someone watching you is directly proportional to the stupidity of your actions"

02-01-2008, 08:30 AM	#6
tx71smallblock Registered User Join Date: Jun 2007 Location: Georgetown , TX Posts: 166	Re: High idle speed Has after market heavy spring, brand new carb, idel screw is backed all the way out __________________ 70 Chevy C-10 short step 250/3 on the tree Owned: 71 longbed Cheyenne 70 swb

02-01-2008, 11:52 AM	#7
haysonj Registered User Join Date: Dec 2007 Location: Santa Maria, Ca. Posts: 1,423	Re: High idle speed Your secondaries are partially open could be bent rod or just dirty or out of adjustment try to manually close them or look down in the carb to see if one of the screws has come off the butterflies. You should also check the choke cam to make sure it is not holding the throttle open __________________ 69 Chevy 4x4 383 Power Last edited by haysonj; 02-01-2008 at 12:00 PM.

02-01-2008, 12:40 PM	#8
Kager67 what knocking sound? Join Date: Feb 2005 Location: good ol North Dakota Posts: 148	Re: High idle speed Something you could try is to hook up the choke and turn the choke housing a quarter turn counterclockwise (lean). This should make sure the choke isn't part of the problem. My 72 did the same thing and this fixed it. Kage __________________ 1968 C-10 1953 belair two-door post 1955 chevy 3600 big window 1950 studebaker starlite coupe 1968 Impala SS

02-05-2008, 10:56 AM	#10
tx71smallblock Registered User Join Date: Jun 2007 Location: Georgetown , TX Posts: 166	Re: High idle speed ok fixed the high idel, the choke cam was holding the throttle open. but now i have a timing question, is the listed 8* btdc before or after you hook up the vacuum advance back up? should i be ideling at 8 with everything buttoned up? or ideling at 8 with the vacuum pluged and then it jump to 10 or 12 with it connected? __________________ 70 Chevy C-10 short step 250/3 on the tree Owned: 71 longbed Cheyenne 70 swb

02-05-2008, 12:41 PM	#11
cruiserman Registered User Join Date: Dec 2006 Location: Idaho Posts: 210	Re: High idle speed 8* base timing, so with vac advance disabled. __________________ 72 C2500 LWB 402 Sierra Grande 05 Odyssey 08 Tundra

02-06-2008, 09:46 AM	#12
tx71smallblock Registered User Join Date: Jun 2007 Location: Georgetown , TX Posts: 166	Re: High idle speed thanks cruiserman, is that what most of you are running? with what i put on it should i run somthing different? __________________ 70 Chevy C-10 short step 250/3 on the tree Owned: 71 longbed Cheyenne 70 swb



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