A mystery on my daily driver, an 85 Caprice with 305 and qjet .

Temps are 20 to 40 degrees. I can start the car, drive it down to a certain intersection, about 3 miles away. At this point, if I am at a light, I can hear the engine start to idle a little rough. I take off from the light OK, then it will stall as I am going about 20 to 30 mph. I have to put it in neutral and restart, hoping I don't need to make any evasive maneuvers with no power steering and no poewer brakes !! Then am on my way , except once there was bad hesitation for a few minutes after the stall.
It doesn't stall every day, really more like once every 4 or 5 days.

My ideas are :

1) Electric choke not quite right.

2) My 180 thermostat is too cold. ( 195 stock)

3)Water in gas.

4) I need to rehook up the hot air intake thing, which I disconnected just before this started. It was stuck on always taking in hot air, so I disco'd it.

5) Head gasket leaking coolant into some cylinders, only at certain engine temp.

Thanks for any ideas.

 

Do you let it warm up or just start it and run?

Check out the distributor too, here's a link I think this would cover another possiblity. It's on the page somewhere http://www.camaros.net/techref/ftecref5.html

 

Finally figured this one out. Disabling the hot air flap setup in the air intake was causing the stallout. I cleaned out the sensor with carb cleaner, hooked everyhing back up, and now it's fine.

 

Glad to hear! It's always the simple things that get you worried too.

------------------
--Steve S--
1984 Trans Am 305 LG4, 5 speed
Daily Driver, Flowmaster 80 Series

 

Yeah, what you're experincing is called "carb icing." With no hot air going into the top of the carb water vapor (from the air) starts to freeze onto the throttle plates gradually choking off air supply and causing idling and off-idle problems. In extreme cases it can actually start icing in the VENTURI and the engine will start to get sluggish even on the highway!

The reason it restarts OK is that once the engine stops the ide IMMEDIATELY melts! It's the evaporation of the fuel going past the throttle plate that super-cools it and allows the icing to take place. Engine stops, no more fuel, no more super-cooling, no more carb icing. But it's damned mysterious the first time you have to diagnose it, huh? All carbs have this problem to some extent.

Once it gets above about 45* outside you can again deactivate the hot air stove with no adverse effects (summertime).


[This message has been edited by Damon (edited February 14, 2001).]