Truck is not running right. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

skokie · 03-04-2008, 10:41 AM

Ok I changed the oil in my 01 sierra and then pulled up the 68 to change its oil. After it was done I started it and after a minute or so it started running bad. It was going down to 500 rpm and would try to go dead unless I gave it gas. Since I was planning a putting the new qjet with the electric choke on it I left it and came back to it tonight.

I put the new carb on qjet 17066553 and it is running a little better but it will idle at 800 then go down to 650-700 then back up to 800. Its got me stumped on what it could be. Any one seen this before?

Thanks in advance.

CCCC · 03-04-2008, 12:16 PM

With the little bit of info available, my first thought would be a vacuum leak - that is, some vac line or connector is open - and the intake is sucking air after the carb mix. With the idle speed fluctuation, sounds like it may be an intermittent leak. Maybe a line or connector was bumped in the oil change operation - posibly at the brake vac booster or ??? Hope this helps.

72swb_327stroker_? · 03-04-2008, 12:45 PM

yup,

sounds like a vacuum leak.

berencam · 03-04-2008, 12:47 PM

i agree with the vacuum leak also but its kinda odd it happened right after a oil change..... did you mabee nick a vacuum line or something while you where in there?

skokie · 03-04-2008, 10:14 PM

I checked the vac lines behind the intake. One goes to the 400 turbo and the other is to the vac guage. I will check the other end of the line going to the tranny and the brake booster. Also when I changed the carb I put on a new gasket on the intake.

skokie · 03-05-2008, 01:45 AM

One more thing to add to this is could my hei coil be going out?

Bus Ted Knuckle · 03-05-2008, 02:06 AM

Vacuum leak, not your coil going out. Could be a vac line cracked, or worn throttle shafts, or bad power brake booster, or vac line going to the power brake booster.

skokie · 03-06-2008, 09:47 AM

Ok here is the latest. I checked/changed where needed my vac lines so that is good. The only thing that I did was go from a wix 51060 oil filter to a 51061. I called the parts store and was told the only difference between the two was that the 51060 had the drain back valve and the 51061 does not. Just for the heck of it I am going to go down there tomorrow and pick up a 51060 filter. I dont see why it would work but it why now.

skokie · 03-07-2008, 07:30 AM

Ok I have checked every vac line I can find and put in the same part number that I took out same thing. Dont know what else to check so I will be taking it into the shop tomorrow. Will post back when they tell me what it is.

AlienYouth · 03-07-2008, 07:38 AM

I'm having the same problem, im not too worried cause i'm puttin in a new motor soon, but it would be nice to have fixed for the next few weeks

68C15 · 03-07-2008, 07:38 AM

it sounds to me like you have had 2 seperate problems. HAD 2, now just one. the first sounds like a stuck float, plugged air bleed in the carb, etc. doesnt matter much now that you changed the carb.
the current problem with the hunting idle sounds like it may be a vacuum advance on the verge of advance. pull the hose and see how it acts.
I remember recently someone here had a link to a retired GM engineer who did a write up on vacuum advance tuning. any leads people?

Sport/Truck · 03-07-2008, 07:40 AM

Use an unlit propane torch to find your vacuum leak. I know sometimes you want to light the torch! But you'll regret it later.
use the propane to check the shaft seals on the carb too.
s/t

joedoozer · 03-07-2008, 09:28 PM

Yeah and that Power Brake Booster idea is a good one. You did drive it, and hit the brakes. Possible it went bad.

skokie · 03-09-2008, 04:08 AM

Had the truck towed to the shop. As I was leaving they started it up and it was blowing blue smoke out of both pipes.

haysonj · 03-09-2008, 04:17 AM

Sounds like you did something to the carb when you changed the gasket. maybe stuck the floats

skokie · 03-10-2008, 01:14 AM

Ok I got a call from the shop and it was a few different things.
1. carb out of adjustment (guilty I tried) LOL
2. dizzy cap loose
3. and the biggest one was that most of my valves were to tight.

The mechanic said that my valves were over tightened. It was probably like that since I got the crate motor. I have not touched the valves. In short he said its running great. He adjusted the valves, adjusted the carb, and set the timing.

He also said that he had a 68 LWB a few years ago and sold it. My truck reminded him of what a mistake he made

Said that he loved how easy it was to work on these. On my way to pick it up. Thanks for all of the suggestions for the help. It is greatly appreciated.

Sport/Truck · 03-10-2008, 01:20 AM

skokie · 03-10-2008, 02:28 AM

Quote:

Originally Posted by Sport/Truck

hahhahahahah

skokie · 03-11-2008, 03:22 AM

I drove the truck today. Big difference even sqweaked the tires when going to second

**Boog** · 03-11-2008, 07:41 AM

Well now. That's sounding better. You've gotter on the road now.

skokie · 03-11-2008, 08:49 AM

Yep. It was like it was sick and when it chirped 2nd it was saying im all better now

03-04-2008, 10:41 AM	#1
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Truck is not running right. Ok I changed the oil in my 01 sierra and then pulled up the 68 to change its oil. After it was done I started it and after a minute or so it started running bad. It was going down to 500 rpm and would try to go dead unless I gave it gas. Since I was planning a putting the new qjet with the electric choke on it I left it and came back to it tonight. I put the new carb on qjet 17066553 and it is running a little better but it will idle at 800 then go down to 650-700 then back up to 800. Its got me stumped on what it could be. Any one seen this before? Thanks in advance. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-04-2008, 12:16 PM	#2
CCCC Registered User Join Date: Mar 2007 Location: San Pedro River, SE Arizona Posts: 734	Re: Truck is not running right. With the little bit of info available, my first thought would be a vacuum leak - that is, some vac line or connector is open - and the intake is sucking air after the carb mix. With the idle speed fluctuation, sounds like it may be an intermittent leak. Maybe a line or connector was bumped in the oil change operation - posibly at the brake vac booster or ??? Hope this helps. __________________ CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp

03-04-2008, 12:45 PM	#3
72swb_327stroker_? knuckle buster.. Join Date: Oct 2007 Location: Frisco Posts: 613	Re: Truck is not running right. yup, sounds like a vacuum leak. __________________ _______________________________________________________________________________ Eric THIS SITE ROCKS!!! Check out my suburban on 20's with fresh paint! Click here to support the site Check out the Member Photo Gallery here StreetCruizin FAQ thread Site vendors list (scroll down to vendors in red) join the the smilies fight club

03-04-2008, 12:47 PM	#4
berencam Registered User Join Date: Aug 2007 Location: branson mo Posts: 933	Re: Truck is not running right. i agree with the vacuum leak also but its kinda odd it happened right after a oil change..... did you mabee nick a vacuum line or something while you where in there? __________________ 69 chevy c10 350 3 speed manual wood bed build thread here r.i.p. 70 c10 auto 350 build here

03-04-2008, 10:14 PM	#5
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: Truck is not running right. I checked the vac lines behind the intake. One goes to the 400 turbo and the other is to the vac guage. I will check the other end of the line going to the tranny and the brake booster. Also when I changed the carb I put on a new gasket on the intake. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-05-2008, 01:45 AM	#6
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: Truck is not running right. One more thing to add to this is could my hei coil be going out? __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-05-2008, 02:06 AM	#7
Bus Ted Knuckle Son of a gun Join Date: Jan 2007 Location: Hot Springs, Arkansas Posts: 1,636	Re: Truck is not running right. Vacuum leak, not your coil going out. Could be a vac line cracked, or worn throttle shafts, or bad power brake booster, or vac line going to the power brake booster. __________________ Bill BEATERS ARE NEATER Last edited by Bus Ted Knuckle; 03-05-2008 at 05:00 AM.

03-06-2008, 09:47 AM	#8
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: Truck is not running right. Ok here is the latest. I checked/changed where needed my vac lines so that is good. The only thing that I did was go from a wix 51060 oil filter to a 51061. I called the parts store and was told the only difference between the two was that the 51060 had the drain back valve and the 51061 does not. Just for the heck of it I am going to go down there tomorrow and pick up a 51060 filter. I dont see why it would work but it why now. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-07-2008, 07:30 AM	#9
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: Truck is not running right. Ok I have checked every vac line I can find and put in the same part number that I took out same thing. Dont know what else to check so I will be taking it into the shop tomorrow. Will post back when they tell me what it is. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-07-2008, 07:38 AM	#10
AlienYouth Registered User Join Date: Apr 2007 Location: Westminster, Maryland Posts: 411	Re: Truck is not running right. I'm having the same problem, im not too worried cause i'm puttin in a new motor soon, but it would be nice to have fixed for the next few weeks __________________ Picturesss 71 C10 383/TH400 13.65 @ 99... 2.06 60' spinnin :/

03-07-2008, 07:38 AM	#11
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	Re: Truck is not running right. it sounds to me like you have had 2 seperate problems. HAD 2, now just one. the first sounds like a stuck float, plugged air bleed in the carb, etc. doesnt matter much now that you changed the carb. the current problem with the hunting idle sounds like it may be a vacuum advance on the verge of advance. pull the hose and see how it acts. I remember recently someone here had a link to a retired GM engineer who did a write up on vacuum advance tuning. any leads people?

03-07-2008, 07:40 AM	#12
Sport/Truck Sierra Grande Club Join Date: Jan 2007 Location: New Mexico USA Posts: 2,433	Re: Truck is not running right. Use an unlit propane torch to find your vacuum leak. I know sometimes you want to light the torch! But you'll regret it later. use the propane to check the shaft seals on the carb too. s/t __________________ 1971 GMC Sierra Grande, 1/2 ton short wide, original 4 bolt 010 020 block & heads. (matching #'s). 383 stroker, SMI q jet 750 cfm, Lunati Voodoo 60102 cam, Scorpion roller rockers, Spin Tech pro street mufflers with X pipe. Last edited by Sport/Truck; 03-07-2008 at 07:42 AM.

03-07-2008, 09:28 PM	#13
joedoozer is Certifiable Join Date: Feb 2008 Location: Hinesville, Georgia Posts: 160	Re: Truck is not running right. Yeah and that Power Brake Booster idea is a good one. You did drive it, and hit the brakes. Possible it went bad.

03-09-2008, 04:08 AM	#14
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: Truck is not running right. Had the truck towed to the shop. As I was leaving they started it up and it was blowing blue smoke out of both pipes. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-09-2008, 04:17 AM	#15
haysonj Registered User Join Date: Dec 2007 Location: Santa Maria, Ca. Posts: 1,423	Re: Truck is not running right. Sounds like you did something to the carb when you changed the gasket. maybe stuck the floats __________________ 69 Chevy 4x4 383 Power



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03-10-2008, 01:14 AM	#16
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: Truck is not running right. Ok I got a call from the shop and it was a few different things. 1. carb out of adjustment (guilty I tried) LOL 2. dizzy cap loose 3. and the biggest one was that most of my valves were to tight. The mechanic said that my valves were over tightened. It was probably like that since I got the crate motor. I have not touched the valves. In short he said its running great. He adjusted the valves, adjusted the carb, and set the timing. He also said that he had a 68 LWB a few years ago and sold it. My truck reminded him of what a mistake he made Said that he loved how easy it was to work on these. On my way to pick it up. Thanks for all of the suggestions for the help. It is greatly appreciated. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-10-2008, 01:20 AM	#17
Sport/Truck Sierra Grande Club Join Date: Jan 2007 Location: New Mexico USA Posts: 2,433	Re: Truck is not running right. __________________ 1971 GMC Sierra Grande, 1/2 ton short wide, original 4 bolt 010 020 block & heads. (matching #'s). 383 stroker, SMI q jet 750 cfm, Lunati Voodoo 60102 cam, Scorpion roller rockers, Spin Tech pro street mufflers with X pipe.

03-11-2008, 03:22 AM	#19
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: Truck is not running right. I drove the truck today. Big difference even sqweaked the tires when going to second __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

03-11-2008, 07:41 AM	#20
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,118	Re: Truck is not running right. Well now. That's sounding better. You've gotter on the road now. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

03-11-2008, 08:49 AM	#21
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: Truck is not running right. Yep. It was like it was sick and when it chirped 2nd it was saying im all better now __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

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