85 Chevy Caprice High Idle When Warm

Hi,

My 85 Caprice 305 sometimes idles too high at stop signs. Sometimes it will kick down, sometimes not. The problem is worse when the weather is cold. I've sprayed carb cleaner inside the carb and on all the linkages.

Once it warms up and I shut off the engine and restart, it idles normally, but once I drive it to the next stop sign, the high idle is back (sometimes, not always) and won't kick down.

I checked for voltage at ther wire going to the electric choke, and yes, it has voltage.

Could it be I need to drill out the rivets and replace the electric choke coil?

I had the hood up on a hot day with the hot engine idling high, and the thing would not kick down as I goosed the throttle repeatedly. But then I manually pushed down the brass colored tab on the passenger side of the carb one notch and the idle dropped, engine still ran fine, then I pushed it down again one more notch, and the idle dropped again, ensine ran fine. I've sprayed the heck out of the shaft going from the choke into the carb too.

Oh yeah, sometimes, not always, I get black smoke when starting it warm, and need to hold the pedal all the way down, and get a good long screech from a fan belt.

BTW the choke pull off valve is OK and working correctly. Already replaced it a few years ago.

Is there something else I have to clean off? Time for new electric choke coil?

Thanks

Reply to
Caprice85
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"Caprice85" wrote

You'll also get voltage at any random wire dangling in the air. You need to see if there's actually current flowing through the choke coil, if it's heating up, and if there's any other mechanical problems with it.

If you hold back the various linkage "notched" parts, does the choke plate seem to be held closed by something springy, or does it just flop around?

Quite possible. The back side of the coil unit looks like this:

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The bi-metal springy thing holds the choke linkage "closed" when it's cold, and should uncoil when it's hot, dragging the linkage with it.

If the bent "tang" at the outer end of the coil isn't properly engaged with the "fork" that connects to the linkage, it won't work.

If the inner part that goes in the slot in the central locating shaft is broken, it won't work.

If the heater element inside the big flat disk part is bad, it won't work.

If there's a bad connection at the power wire to the carb, or a bad ground from the carb, the heater won't heat up, and it won't work.

If you have one of the GM models with a 2-pin oil pressure switch that runs the oil light AND the choke coil at the same time, and there's a wiring problem or it isn't plugged in properly, the choke coil won't work.

Reply to
MasterBlaster

Check to make sure your solenoid is not kicked in on other side of Carb.

Reply to
BigFoot

My 86 caprice had an idle speed motor that would advance the idle speed when the AC was on. I think it also had a pressure switch on the power steering and when the PS pressure when over a certain level, such as turning the wheels when you were not moving very fast, that also kicked up the idle speed. This may or may not be the case with your 85. If you do have the same thing it will be on the drivers side of the carb.

Reply to
Ashton Crusher

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