Hey everyone. So I have an '89 RWD Cadillac powered by an Olds 307 and I have an issue with the car returning to fast idle after driving. I'll start the car up cold, it'll warm up but the idle doesn't come down unless I give the throttle a forceful tap. Idle comes down, I'll put it in gear and drive around for a little while. Next time I throw the car in park the idle speed goes back up and stays there unless I give it another good tap. Mind you, if I simply press and release the throttle, like a normal rev of the engine it won't come down. It has to be a forceful tap so to me that feels like something is sticking. I've sprayed everything down, moved the fast idle cam myself, I've even shot carb spray into the choke thermostat but nothing seems to help. My choke is a factory sealed part with three rivets holding it in place, so I haven't actually removed it to make sure everything is okay. Does anyone have any advice for me before I go drilling these things out? As far as I can tell everything seems to be moving correctly.

 

There isn't actually much inside the choke besides a coil. If something's binding it could be the linkages coming from the choke or some of the small parts behind it.

 

If its releasing with a tap, it most likely is the choke. Look at the flap on top of the carb and see if its all the way open when this happens.

 

Thanks for the tip. I'll have to take a look at this next time it sticks. I'm guessing if the choke is even partially closed then this would indicate sticking by the thermostat?

 

Did some searching from the "Related Topics" section below and stumbled upon one of you guys with an 80s Cutlass having the same issue. This came up.

"The secondary throttle plates are on the bottom of the carb. If they are not closing fully, the engine will race, even if the air valves are closed (the air valves do not completely seal to the air horn). If the engine is racing, shut it off without touching the throttle. NOW hold open the air valves and look down inside the secondaries. The throttle plates MUST be completely closed."

I know exactly what those are and didn't even consider looking at them. I love how on this site I find tons more helpful info about my engine than on the Cadillac board. 307 cars are a dime-a-dozen here as opposed to the 5 model years of Cadillacs to work with on the other board.

 

the choke plate has to open completely when hot or it will still be on hi idle cam,there are multiple steps on the cam.is it electric choke thermostat?

 

It's a stove pipe choke so it should only have one step. I've noticed that the choke plate is open when I'm experiencing the high idle in Park.

 

Look at the choke linkage step and see if the high idle speed adjustment screw is still in contact with it. If not look at the accelerator linkage and see if its sticking, idle speed adjustment screw is not making contact with the stop.

 

it has to be completely open,stabbing the gas pedal can draw the choke plate open and take it off the hi idle cam.i have seen many times on that vintage the vacuum port in the base plate of the carb that supplies vacuum to the choke housing causing hot air to circulate by the spring become clogged with carbon/sludge and the spring doesn't get hot enough to fully open.if you can hold your finger on the pipe to the middle of the intake it's not getting hot enough.

 

Great advice guys, I'll have to check these to make sure everything is operating correctly.

 

Okay, found the problem. As soon as I pop the throttle cable off the idle drops down where it should be. It doesn't stick any more after that so, new throttle cable it is.

 

Glad you found it.