NathanVos

Got an issue that had me stumped. Wondering if anyone else had any ideas or has had this happen. 1982 22r pickup. This problem just appeared three days ago. The engine was running fine before. Carb rebuilt about 1 1/2 years ago. Engine runs fine at idle when cold. In fact, as long as the engine is running from that first start in the morning, there are no issues of idling or power. Also, if the engine is turned off and immediately started, there are no idling or power issues. However, when the engine is turned off and sits for a half hour or even a few hours, upon starting, the engine sputters when revved and cannot idle as though it is cold with a stuck open choke (which if you read on looks like what it is). It will die if my foot is off the gas pedal. If I rev it for at least a minute or so, the engine will eventually smooth out and be drive-able and the engine will keep a smooth idle.

I pulled the air cleaner top off the engine, the engine had been sitting for three hours after being ran (ran 30 minutes). The choke was completely open. The engine bay was still warm as was the air cleaner assembly. After revving it for a minute and the idle smoothing out, I drove it home and let it set for 30 minutes. Upon inspection, again the choke was wide open. When started, the engine would not idle and sputtered when revved. I forced the choke closed and started the engine, the engine ran at fast idle until I tapped the accelerator. The choke immediately went wide open and the engine sputtered and died. I put the engine at 3/4 choke, started it, and the engine again idled and was smooth on rev if I kept my thumb on the choke to keep it partially closed. If I let up on the choke, it would spring wide open and the engine would die. Letting it run for 30 seconds with the choke closed I let the choke spring wide open, the engine sputtered but was warm enough to keep running. After letting it set about 45 seconds more the engine was warmed up and the idle smoothed out.

It appears that although my choke will eventually reset itself if the engine is completely cold, it will keep itself stuck open if the engine is remotely warm from a previous drive, even if several hours before. I was wondering if something happened with my choke or if there is an underlying issue that an enriched choke setting is compensating that I am missing. It seems like a choke problem, but you never know. Other vehicles I have owned with a stuck open choke generally ran fine if the engine was remotely warm, maybe with a small wait to let it warm up some more before driving, so that is why I am suspicious. Thoughts anyone?

13Swords

Given the detailed info you outlined (good job!) it sounds to me like the choke may be out of adjustment for some reason. Cold engines need a richer air fuel mixture (more fuel than air) to keep running. As an engine warms up a leaner mixture (less gas) is sufficient. Your experiments outlined in the second paragraph show this. The 22R Carburetor has an electric/mechanical choke mechanism. Mechanical chokes do NOT reset themselves just because the engine cools off; they usually stay in the open position, even if the engine is now cold. The choke only returns to the closed position with some input from the throttle linkage, from gas pedal to throttle cable to carb linkage. To verify this, wait until the engine is completely cold, take off the air cleaner and look. The choke should still be completely open. Then give one "pump" to the gas pedal or one full pull on the throttle linkage & release, and the choke plate should snap to the closed position. If it does this the choke is functioning, as far as the general mechanicals of it are concerned. I would check to make sure the whole choke linkage was connected & working, & make sure it's clean & not binding or sticking. Spray carb cleaner applied to the linkage usually takes care of any sticking issues.

Now about the electric part of the choke. There is a bi-metalic spring & a small electric heater in the choke housing. Example picture below (not a Toyota carb choke but this is similar):



The heater gets power anytime the ignition switch is on (engine running or not) & heats up the coil spring, which expands (unwinds). The end of the spring is connected to your choke linkage or it has a small tab on the end that pushes on the choke linkage. As the spring expands (at a preset rate) it gradually pushes on the linkage more & more, progressively opening the choke plate. When the ignition switch is turned off the heater turns off & the spring eventually cools & contracts back to it's original position.

Barring any other problems, either the choke spring has slipped out of adjustment opening the choke plate too quickly, or the spring has lost some of it's "spring" & gotten a little larger over time from use. You may be able to adjust this. The choke housing usually has a retainer ring on it with three screws that you can loosen & rotate the housing to make an adjustment. I say "usually" because I have run across a few that had rivets in them instead of screws; you'll have to see what you have. If riveted you can (carefully) drill out the rivets & replace with small nuts & bolts with spring/lock washers. In either case, loosen the retainer ring and rotate the housing towards the driver's side of the vehicle a bit. There should be marks on the housing on top; rotate back 1 mark, tighten down the retainer ring & test again as you have done before. While you're there also check that the electric connection to the housing is on firmly & is clean. There should be only 1 wire going to the housing (hot wire); the heater is grounded through the carb so there is no negative (-) wire. By the way, it sounds like the heater part IS working, as you are able to "kick it down" after running for a bit, so that's why I think it's an adjustment problem.

Hopefully this will get it solved. If not let us know & we can try & go from there.

NathanVos

Thanks for the response. Now that you mention this, that gives me a theory. When I rebuilt the carb a while back I did have to drill out the rivets for the choke housing, and I had to use small bolts and nuts to keep the thermostat on. I bet vibration has made the housing loose causing it to go out of adjustment. I will update on this when I get a chance to give this a look.

13Swords

No problem, that's why I mentioned using spring or lock (star) washers; keeps the nuts from backing off. Of course the easiest solution to it not happening again is using a drop of Loctite Blue threadlocker on each screw/nut connection. Will keep them from vibrating loose & can be undone later if needed with handtools.