Hi guys. I have a 69 Skylark and am having some serious idle problems. The choke opens up all the way on startup, and wont ease up. It sounds like someone has the gas floored. When I took a look under the hood, there didn't seem to be any tension on the arm to ease up on the choke coming from anywhere...I'm at work right now, but I believe my carb is a 2 barrel Rochester. This happened a few ties before, but ususually with a couple of good revs, the idle would die down. Bear with me cuz I'm a bit new, and don't know much about carbs yet... Any ideas? Eric
Typically, the cold idle is controlled by a cam on the driver's side of the carb. This cam is controlled by the choke bimetal coil in the housing mounted on the side of the carb. As the air enters the air cleaner, it is heated by the exhaust manifold. The heated air is drawn into the intake manifold crossover, where it is futher heated, and drawn into the choke housing via a small intake manifold vacuum leak on the carb itself. This heated air is used to heat the bi-metal choke coil, which opens the choke, and allows the fast idle cam to slowly drop. Ths cam controls the idle by holding the throttle open, until it is fully down, where the normal idle returns. If the choke opens completely, it is likely a sticking cam or linkage. If the choke is not opening completely, look for a defective air cleaner heater, leaking choke housing, or binding linkage. Let me know...
aha....i had the air cleaner off so this is probably why the fast idle stayed on. ou: This makes sense regarding the times this happened before as well, since the return to the air cleaner was not always firmly attached. is there a diagram or picture somewhere so I could see which screw is the fast idle? it seems way too high... Eric
Eric, here's how I set fast idle cams. It's hard to explain, but it will get you into the ballpark..........first make sure nothing is binding.......spray everything really well with carb cleaner, especially where the choke shaft goes through the sides of the carb. THEN, warm up the motor, and make sure the ckoke is opened all the way. Then shut off the motor, and place the fast idle cam all the way down to the lowest step......that's the one where it's at when fully warmed up. Then, with your finger, open the throttle just a little and place the cam on the next step......that'll be the one just above the lowest step. Your idle should only be about 50-100 rpm's higher on this step than on the lowest one. (This equates to about 1/2 turn on the screw from the point where the surface of the second step just touches the tip of the screw.) You could set your fast idle to about 1500 RPM on the highest step, but the way I explained it always worked better for me on my old Skylark. Do you get what I am trying to say? o No:
Normally, the hot idle, at the curb idle setting is the way to go. With the engine warm, set the curb idle to the factory settings, and the fast idle will take care of itself. Though it is possible to adjust the fast idle separately, it will require modifying the fast idle cam. This goes for the two barrel carb only. The four barrel carb has separate fast and curb idle screws. Let me know... Ray
ou: I should have read his original post more carefully, I was thinking he had a Qjet. It really sounds like the problem is sticking linkage, you might also want to make sure your choke pull off is working and adjusted properly. :bglasses:
I think what he means is that on start -up the choke goes fully closed (not open), and won't come off, Most chokes are adjusted by backing off the three screws on the housing and turning the housing(black plastic) until the choke opens/closes. Hope this helps.
My carb says Rochester 2 Jet on the top. I'll try to find the number on it later. Have to go get some tubing at Autozone for the air cleaner to valve cover connection. I didnt see a fast cam screw on the passenger's side. Only the large one on the driver's side. Does this control both the fast and regular idle speed? The two screw pointing forwards on the front are the mixture screws, correct? o No:
Correct. The slow idle is part of the fast idle setting. The two barrel was very difficult to adjust the choke properly. Be sure that the choke is getting sufficient hot air, and be sure that the heated air cleaner is supplying sufficient hot air to the housing. If the chain here is broken anywhere, the result can be a choke not opening. Do this before making any adjustments. Ray
update Well, I finally had a rain free weekend to fix one of hoses from the valve cover to the air cleaner, but my high idle is still stuck. Should/can I replace the choke altogether? Or go whole hog and replace the carb and go electric? How hard is this? Eric
