I guess this is the place to ask. I have a 84 GMC truck I use for wood cutting and the sand dunes and lately it stays on high idle. It has a 355 Q jet 4 bbl electric choke. I have cleaned the carb inside and out and it still has a high idle ,is this the choke controler on the carb that wont let it come off or something else? Any help would be appreciated.
Q jet ??? non buick
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Just some random thoughts
It's been years since I've even seen a Q-Jet but it sounds more like a vaccum leak to me. I would check all the vaccum lines for leaks/cracks. There is also an idle screw on the leakage that may need adjusting. I also had an issue once with the A/C idle control sticking and causing the idel to run high. It's a little eletric solenoid that should be mounted on the Carb. When you cut the A/C on it clicks the solenoid on to ajust the idle. The one I had ended up magnitised or something and always tried to ajust the idle.
It's been years since I've even seen a Q-Jet but it sounds more like a vaccum leak to me. I would check all the vaccum lines for leaks/cracks. There is also an idle screw on the leakage that may need adjusting. I also had an issue once with the A/C idle control sticking and causing the idel to run high. It's a little eletric solenoid that should be mounted on the Carb. When you cut the A/C on it clicks the solenoid on to ajust the idle. The one I had ended up magnitised or something and always tried to ajust the idle.
jhanson1750
just a 10th quicker
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You may need to adjust the choke. If you look on the pass side around the choke eletric plug are three screws you have to loosen the screws and the black round thing will twist. You have to play with it as I've not messed with them in years. But if memory serves me it has some printing on it that may help. It sounds like the change in the temps has made the choke no longer close. Or it may just be stuck. I agree with checking the vac lines as well. If you look on the pass side there is also a idle screw for the choke at least I think it is on the Qjet.....Been a LONG LONG time sence I worked in a leaker!!!! Good luck Jon Hanson
The truck has no A/C and yes I know how bad the Q jet can be but the cost of a new edelbrock is rediculous for what I use the truck for. I will check for vacume leaks. It started acting up this summer so temp is not an issue. Im no good at carbed vehicles. I need a computer to figure things out. lol. I do have a Holly 600 that was given to me I could rebuild but the truck has ran great for years and I dont want to mess with it. Thanks for the help.
Now I can tune the Eldlebrocks for some reason but I still perfer the Holley over both w/electric choke.Nothing wrong with Q-jets..It maybe in the choke, when warmed up is the blades open all the way??? also if the wire going to the choke isn't on right or fallen off it idles high. A good book on rebuilding and tweaking Q-jets is Doug Roe's book.
Like as not, it's the choke. The electrical connector likes to break and lose contact. Usually has an Oil/Choke light at the same time.
Check the choke connector to see that it's on. If it is then get it running and after a couple of minutes look at the choke plate. It should be vertical. If it's closed a bit (or a lot) grab a test light and check for power to the choke. If no power then you'll have to troubleshoot the electrics. If power then the choke heater is probably bad.
edit:also, sometimes the fast idle cam sticks. If the choke opens and idle stays high, push down on the fast idle cam counterweight located just inboard of the choke housing (you can't miss it). If that lowers the idle then lube the area with a spray lube.
Check the choke connector to see that it's on. If it is then get it running and after a couple of minutes look at the choke plate. It should be vertical. If it's closed a bit (or a lot) grab a test light and check for power to the choke. If no power then you'll have to troubleshoot the electrics. If power then the choke heater is probably bad.
edit:also, sometimes the fast idle cam sticks. If the choke opens and idle stays high, push down on the fast idle cam counterweight located just inboard of the choke housing (you can't miss it). If that lowers the idle then lube the area with a spray lube.
It stays fast idle till I hit the cam and push it down that you talked of but once I give it gas it ratchets the choke on I guess and I have the high idle. I havnt checked for power thou cant find the dang test light. I Sprayed carb cleaner and lube on it to no avail. I guess I dont know what keeps the choke from coming back on when I touch the gas. I hate carbs....
That's what the electric power is for. It runs a heater element that heats a bimetal spring. The spring uncoils as it warms and that's what opens the choke. Without the power it just doesn't get hot enough. If there is power then the heater element probably fried and the choke thermostat would need replacement. I didn't see this all that often, mostly it was bad connections and other electrical issues first.
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