I have a 1984 Trans Am with a Q-Jet carb. I was driving home from a cruise night when my "Choke" light came on. When I came to a stop the engine would not idle unless I held the gas pedal down slightly. The choke light now stays on and the engine does not seem to be running smoothly. This happened once before and it turned out to be a blown choke heater fuse. This time the fuse looked OK but I changed it just to be sure, but the Choke light remains on. Any ideas?

 

Choke light bulb grounds through the choke heater. The choke heater gets its power from the oil pressure switch on the back of the block. Without the choke heater functional the choke is likely staying atleast somewhat closed.

 

'You sure about that? That's not how it is on my '83. Why would '83 be different from '84?...

 

Is your alternator charging?...

 

I think TL is right, I seem to recall the choke heater relay being controlled by the alternator, such that in normal operation if the alternator isn't spinning & putting out power (usually meaning the engine is not presently running) that the choke won't be being heated on an engine that isn't running & warming up. When the alternator fails it of course acts as if the engine isn't running......

Bonus points; if the relay itself has failed, you CAN get a choke light and still have a functioning charging system, the alternator controls the relay, which controls the heater......

Now, I could be wrong, it's happened once or twice before (and, , , Sofa is usually right there to point it out to me, bless his heart )

Here is your 1984 wiring diagram showing the choke heater relay connected to the "Generator" at the lower left side of the diagram on the brown wire

 

They used a whole bunch of schemes for that circuit in various years.

However all that might be, the "Choke" light is ACTUALLY the "Alternator" light. For whyever, probably EPA regulations or some such, it was thought more important to warn the car's user that the choke wasn't working right, than that the battery wasn't getting charged. The reason for all this is that the charging circuit and the choke heater circuit are intertwined such that the choke heater won't get power (and therefore won't pull off) unless the alt is charging, which prevents the choke heater from getting heated if the key is on but the engine is not. And if the choke doesn't pull off, the car will be MASSIVELY rich, like black smoking rich, and obviously this is an emissions issue. Butt rather than tell you what's REALLY wrong ("I'm having a heart attack"), it tells you about some minor symptom ("my face is turning grey"). W/E.

So, first thing to check when the "Choke" light won't go off, is the alternator. About 99.999% of the time that's the problem. The other .001% of the time, it's some one of ALL OTHER possible causes. No need to even start thinking about those yet.

Start at the alternator. Use your digital multimeter to measure some voltages. What's the voltage between the Big Red Terminal on the back of alt and the case, when the car is running? What's the voltage across the battery terminals - the TERMINALS themselves, the physical parts of the battery itself, NOT the connectors, NOT the wires, NOT ANY OTHER parts - at the same time?