455man

I have a quadrajet 1708213 from a 1980 chevy 350(5.7l) truck. I put an electric choke on it when it was rebuilt. I'm having problems with cold idling. I have to keep my foot on the gas or it will die. After a couple of minutes it idles fine. It's 70 degrees here in the morning and 95 in the afternoon. I turned up the fast idle so it would stay running but then once it's warm it idles about 1300 RPMs. I assumed at this temp the choke does not need to be on but maybe it needs adjusted too. I have the heat crossover welded shut on the heads. Also I couldnt find a ported vacuum on this carb so I'll assume it does not have one. Air/fuel has been set using a vacuum gauge. Anyone know the process for setting this carb?

Oldsmaniac

There is the curb idle screw for idle and there should be a fast idle screw that controls when the choke is on. Is this the one you are adjusting? It should not come into play when choke is off so you should be able to set idle with the curb idle screw to most any speed you wish. If you cannot you may need to adjust idle mixture screws as they may be set too rich or fuel could be passing from too high float setting or casting plugs leaking in the fuel bowl. You should also make sure your choke pulloff(s) are operating.

455man

Idle screw is on the drivers side and fast idle is on the passenger side. I know which one is which. So the fast idle should not come into play if the choke is not on. I'll assume at 70 degrees or so the choke wont need to be on. When i set the idle screw to idle at say 800 rpm cold then when it's warm it idles at about 1300 rpm. Idle screw seems to work fine. It's the cold idling that's the problem. Choke pulloff seems to be working. Vacuum sucks it in when it starts.

MDchanic

Your description is not completely clear.

You should adjust both of these screws (and the mixture screws) when fully warmed up, only.

There is a specified engine speed for a specified step of the fast idle cam when the engine is fully warm (for either the 1980 truck or for your car - take your pick). You do not adjust the fast idle with the engine cold.

- Eric

455man

Ok. I was not aware of the fast idle needing to be set when it's warm. Do i set it to a certain RPM? Also I did not see multiple steps on the fast idle cam. I'll see if I can take pics after work.

oldcutlass

The stepped linkage of the choke fast idle screw overrides the normal curb idle setting. When the choke is engaged it lifts the linkage higher than the normal curb idle setting. Once the temp rises and the choke disengages the linkage drops and then the normal curb idle screw takes over and sets the minimum operating rpm.

MDchanic

Yes, take a close look, you should see two or three steps.

The tune-up instructions in the CSM for either the Olds or the 1980 truck will tell you where to set it.

I should have a scan of the truck manual at home if you want it.

- Eric

455man

Checked wild about cars on a 81 Olds carb. I'll give it a shot again tonight and see what i can figure out.

MDchanic

Not an 81 Olds carb.

Your car is a '72 with a 455.

Depending on your engine's modifications, you need to use the original specs of the carb ('80 Chev truck), the original specs of your engine, or some logically derived combination that makes your engine run well.

- Eric

455man

Gotcha. I was trying to find something similar to the carb I had. I made some adjustments last night. Found the 2 steps on the fast idle. It idled better this morning but when i got to work it was idling at 1300 RPM's in park. So I'm back to square one.

oldcutlass

Seems to me it's not coming off the choke settings. It also could be binding linkage.

MDchanic

Yes, are you sure that the fast idle cam is falling all the way to the bottom step when the choke is off?

- Eric

455man

I'll double check that tonight MD.

455man

A little update. I noticed my air cleaner housing was rubbing against the choke lever and keeping it partially shut. I had a spacer under the housing that caused that. Took off the spacer. Runs better now but still wanted to die this morning when cold. I'll play with it this weekend.

455man

It has not been cold enough to mess with the choke til recently. So i found out my electric choke was bad which explains why I was having problems setting the fast idle. Put on a new one. It runs better but still trying to get the fast idle set right.