Carb going lean
12-23-2016, 04:24 PM
#1
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Carb going lean I've been noticing that when the engine is cold (temp here is about 40 - 45*F) it idles very rich, like 10.5 - 11 afr. As it warms up, it goes into the 12's and when it's fully warmed up it gets to about 13.5, but keeps going. So after a long drive it's working itself up to 15 and then 16, until it leans out so far that the engine dies. I pulled over and opened up the mixture screws a half turn, which is pretty big, but still did the same thing. The rest of the fuel curve is fine, maybe even a little rich, just the idle that goes completely lean once the car fully warms up.
If I hit the accelerator, it bounces back to normal but then instantly does the same thing.
Carb is a holley 650 on a stock 5.3. Any help would be great. Thanks.
If I hit the accelerator, it bounces back to normal but then instantly does the same thing.
Carb is a holley 650 on a stock 5.3. Any help would be great. Thanks.
12-24-2016, 05:16 PM
#2
Does it have a choke? Electric or manual?
When it is hot and lean check for vacuum leaks. Maybe a gasket it opening up as the motor gets warm and expands.
Does the carb feel hot when it is going lean? Do you have any sort of isolator under the carb? I think they are called phenolic gaskets, basically a plastic carb gasket, something to block manifold heat from the carb base. I had to add one to my car.
When it is hot and lean check for vacuum leaks. Maybe a gasket it opening up as the motor gets warm and expands.
Does the carb feel hot when it is going lean? Do you have any sort of isolator under the carb? I think they are called phenolic gaskets, basically a plastic carb gasket, something to block manifold heat from the carb base. I had to add one to my car.
