Truck is not running right.

[skokie]

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]

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_?]

yup, sounds like a vacuum leak.

[berencam]

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]

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]

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

[Bus Ted Knuckle]

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]

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]

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]

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]

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]

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]

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

[skokie]

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]

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

[skokie]

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]

[skokie]

Originally Posted by Sport/Truck

hahhahahahah

[skokie]

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

[Boog]

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

[skokie]

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