This condition started this winter. If it's ~40F or below, the choke will go in automatically, but the car will stumble then die. I have to either pull the choke out by hand or press the accelerator. When first starting I set it to idle at 2000rpm, but sometimes it will fade down to 1500 and feel like it wants to go lower. After warming up, the car will hot start normally.

Yesterday it was 60F and it warmed up with no problems.

The car is an '82 12A stock. The only changes to the cooling system is 3 row radiator, new hoses and Mazda thermostat replaced last summer. Plugs, wires, cap, rotor changed in September. Fuel filter was changed last week.

Any ideas? Vacuum leak? The carb preheater hose is intact, but I've heard of people running without one so I don't think it could be that.

 

If you are saying that the choke **** pops right back in, rather than staying out until the car is warmed up, then check in the manual. There is mention of that situation, but can't recall the details right now.

 

The choke **** works off of a magnet. When the temp needle gets past its mark the magnet stops working and it pops back in. There is no electricity supplied to the magnet anymore.

Too me it sounds like the magnet is not at its spot or its not getting enough voltage. The RPM should actually go up as its getting warmer.

It's in the manual instructions on checking it.

-nick-

 

Get a voltmeter and check the water temp sensor in the back of the waterpump per the FSM instructions. If this fails, or isnt working properly, the choke will get the wrong signal.

 

If the choke **** is not staying out on it's own during warm up, check the conection to the sensor on the backside of the waterpump housing. Be careful unplugging the wire connector. The 2 wires that come out of the sensor are brittle and easily broken.

 

Shouldnt it be the opposite though? wouldnt a sensor mess up cause it to stay out all the time?

Im confused....

 

The choke **** can stay out on its own. It's just that when it's pretty cold outside, the choke will stay out, but the rpms will drop down bit by bit to 1500 then it'll try to go lower but can't. Then when it warms up, the temp gauge will read warm, the choke **** will go back in automatically, but the car will die. If I pull the **** out before it dies I can get it back up to a little over 1000. I just have to hold it or push the accelerator till it warms up a little more.

It's just annoying to sputter out at a stop sign.

^I'll check that other stuff. Thanks.

 

Have you checked for vacuum leaks?

 

Sorry to dig this up, but I think there was just some gunk in the carb.

I ran a can of Seafoam in the gas tank for the first time, with about 4 gallons of gas, and it hasn't died since. The idle still kinda falters with the choke out, but it doesn't die. We just had another cold front come by, ~30 in the morning, where I was expecting it to.

 

I had this issue, with a fresh carb and strong motor, I had to remove the fan on the coldest days (20*F and under) because it would barely get into the gauge. Though I never had a stalling issue, just no heat really :p

 

OtakuRX: Sounds like your thermostat is stuck open. 20F isn't really cold... only time I have had trouble getting a car warmed up is when it was -20F! And even then it did warm up eventually, just... took a while.