83

This all first started when I tried to make sure my carb was adjusted...so I set the idle mixture the way the manual describes, but I can't get the idle speed screw to drop the idle any farther, and I'm at around 1200rmps. I'm supposed to have the idle mixture screw turned out to the point where it no longer increases the idle, then set the idle where I want it with the idle speed screw.

I've had this issue with 3 carburators now (don't ask), and I've got a rebuilt one on now with less than 20 miles on it. Same issue. The only way I can get the idle down is with the idle mixture screw, but that's not the correct way to do it, so...Either I'm missing something and not adjusting it right, or it's obviously not a carb issue, since it's happened with all three of them.

At a certain point, the idle speed screw no longer drops the idle. It still turns out more, but doesn't affect the idle. There's plenty of slack in the cable, and I can drop the idle by pulling the throttle closed more. So is there any adjustment point on the actual throttle linkage, or what?

I can get the idle where I want it by using the idle mixture screw, but when it gets down to 8-900ish, I hear a lot of sputtering out the exhaust.

1983sumdaycrawler

I have the same problem right now, but I think I might be going with propane soon. Got a buddy that is gonna sell me a kit, My carb has a bunch of vacuum issues. think thats my idle problem.

83

I don't think I have vacuum issues...but who knows. I've got a vacuum diagram and I've checked & rechecked how it's all hooked up. I guess maybe some of my emissions stuff could still be plugged up or something. If this wasn't my daily driver and road trip vehicle, I'd look into propane.

crazykooter

Pull your throttle all the way open and then look under the leakage. There is a flathead screw there. Its not easy to see but it is another idle screw. This is your high idle screw. Yours may be set to high. If all the adjustments are correct then you have a vacuum leak on manifold or on base of carb. For the idle to increase it needs to be a bigger leak. With your idle mixture screw just shut off motor then turn it in all the way till it stops then back it out 5 turns. Leave it there. Adjusting it will only screw you up more.

83

I didn't think the high idle screw did anything once the truck was warm? I shouldn't have a leak at the base of the carb. This is my 3rd carb, and I just replaced the spacer with a new one from Toyota with the gaskets glued to both sides.

The factory settings for the idle mixture screw is 4 turns out. But the FSM proceedure for setting it is to turn it out till you get the highest idle possible, adjust the idle back down with the idle speed screw, and repeat, until the idle mixture screw no longer raises the idle, then set the idle speed screw to where you want the idle.

So like I said I know that adjusting the idle speed with the mixture screw isn't the correct way, but so far it's the only way I can find to drop the idle. I'll spray around with carb cleaner a bit to see if I can find a leak.

crazykooter

Ya backing it out till it wont raise idle anymore is correct. I just found that its always been around like 5 turns out for me every time.
It may not be a gasket issue. Im thinking along the lines of your intake manifold is not flat. When you installed the manifold did you use red gasket material ? These 22r's and 20r's are know for not having perfect mating surfaces. If thats all correct then you have a vacuum line hooked up incorrectly. When you pull the 2 lines off the distributor is the one closest to the valve still pulling vacuum ?

83

Ok. Yeah that makes sense, I'm sure it's not exactly 4 turns for every carb. I'll spray around my manifold. After removing it and putting it back on twice and still leaking some coolant...I did the unthinkable. I brought it in to a shop. I think that may be the last time in was in a shop. Looks to me like they just used a gasket. Are you talking about red rtv, or what? I'll see if I have a leak there. I shouldn't have a vacuum leak anywhere in the lines, but there could be one at the manifold. I could certainly have lines hooked up wrong, I guess. There is no one vacuum diagram that matches my set up just right, so I'm always guessing a bit on a couple hoses. It could also be that some emissions piece is clogged up.

When I set my timing, I noticed the vacuum advance was working, if that's what you're getting at?

crazykooter

Yes red RTV is what you use. You dont even have to use a gasket, just use the red and lay down a 1/8" bed around the whole thing. Little extra isnt gonna hurt anything. If ur gonna use carb cleaner to check for leak then make sure you use chemtool. Its the best out there for not only cleaning carbs but also finding leaks. Also a good trick if you want to call it that is to get your engine warm and use a longer vacuum hose to put to your ear and move other end around the manifold to listen for the leak. It does work. There is also this http://www.sears.com/shc/s/p_10153_1...0070921x00003c which is made for this purpose. Another way to find very small leaks is to use an air compressor to pressurize your intake system. Max psi for this is about 8 psi I believe. Then get a spra bottle with some dishwashing soap and water mixed. Spray it all over the intake and carb area and see if you see bubbles.
To be honest I find using carb/break cleaner to find leaks very hard since it sprays over a broad range so you can isolate the area but not the specific part or area.
Oh and another thing is if you have a vacuum pressure gauge that will hook up to the intake manifold, messure your manifold pressure and watch the needle. That can tell you almost everything bout the motor because the way the needle reacts can very much help you isolate the issue. Your motor is new I believe so your manifold vacuum should be 18-22 psi or higher. Mine is around 22 psi at idle. Low manifold pressure can tell you it is in fact a vacuum leak while normal pressure tells you to look at an incorrect vacuum setup.
Sorry for long post but thought I would throw some more info hoping it would help.
Laters Josh

83

Ok thanks a lot. No problem on the long post. I'm pretty guilty of writing long posts, but I like to get a lot of info across so people responding know exactly what I'm talking about and what I've tried already so I don't waste too much time.