Engine Stall at idle

[Trev87]

I have a 1973 Camper Special 3/4 Ton with a 350. While driving today when I was stopped at a light or stop sign and took my foot off the gas, the engine would stall. After a few minutes I was able to get it going again. Even when in park or reverse the engine sputters and eventually dies. It drives fine but as soon as I take my foot off the gas it wants to sputter and die. Any ideas of what this could be? Clean the EGR? Faulty Fuel Pump? Clean the throttle body? Any help is appreciated. Thank you

 

[1987 GMC Jimmy]

It’s some kind of fuel/air problem. I’d check to make sure your choke is all the way open at operating temp. Make sure the air filter hasn’t gone bad. Vacuum leaks could also be part of the issue. It’d take a pretty serious one to act up like the brake booster, the carb base gasket, PCV valve... Otherwise, your carb is having issues that would warrant a rebuild, you need a new fuel filter, or your fuel pump needs replacing. If you can draw gas from a can, you can rule out anything behind the pump. If the pump can fill a 20 oz equivalent container in appx. eight seconds, the pump is fine. I would suspect the carburetor if all else fails, but you have to rule everything out first.

 

[Charlie]

 

[75gmck25]

Is the engine original? A '73 Camper Special should have a GVW high enough to qualify for HD emissions, and I didn't think there was an EGR with HD emissions in '73.

First check - If its a Quadrajet, there is an idle speed screw on the driver's side of the carburetor linkage, and you can try just turning it in (clockwise) to set the idle higher. You want it to idle at about 700 RPM while in gear (drive or reverse), so the idle in neutral/park will probably be about 900.

Idle mixture screws on a Quadrajet are a PIA to reach with the engine running because they are tucked up under the front of the carburetor. Too much chance of coming close to a spinning fan. However, there are some simple checks for the mixture.
- With the engine running and warm, put your gloved hand over the carburetor venturi. If the speed goes up, the idle may be too lean due to fuel starvation (plugged filter, etc.) or a lean mixture setting.
- With the engine running and warm, clamp a vice grips over the rubber fuel line near the carburetor. If the engine smoothes out as the float bowl empties and it begins to run out of fuel, it may be running too rich. This might mean a bad float (hole?), debris keeping the needle open, or a too-rich mixture screw.

Bruce