It wouldn't idle down

[don t. - 72gmc]

Went to warm up the beast this morning in very cold N. Ill.
Started right up but something didn't "feel" right w/the gas pedal.
Figured it was just cold, let it warm. About 7 minutes later, got in to go, kicked the choke down, no problem. Put in gear, took off, no problem. Got to 1st stop sign, it didnt wanna slow down, like pedal was stuck down. Threw it in neutral, coasted to sign. By the time I got to sign, pedal back to normal. Kicked it up to 55 and decide to check it. Sure enough high idle (pedal) as before that eventually did die down.

Its warming in garage right now. Initial investigation seems that the acc. pump on the carb isn't comming up immediatly. I haven't taken it appart yet but it goes down smooth, just not comming back up right. I did rebuilt the carb (+or-) a year ago, remember replacing this part. I will post back w/what I find but any ideas on why this woulda happened??

While im there...I initially thought it might have been the throttle cable, icing or such. Can you lube/should you lube this cable. It looks ok from what I can see. Anything else I can look for?

BTW....the last time I drove the truck was last monday, no problem at all. Temp was warmer than today. Usually only gets drove on weekends and monday.

TIA....don t. ....

[don t. - 72gmc]

Have fun...don t. ...

[jhow66]

What kind of carb ?

[71GMC_3/4T]

Sounds like carb icing to me.

[COBALT]

Other than carb icing here's two other alternatives:

1. Choke pull-off not working right and slapping main throttle plate shut when the accelerator is dropped.

2. Throttle return spring is worn out.

One time I was replacing my thermostat and forgot to reconnect my throttle return spring when I was done. I got one hell of a surprise when I fired the truck up and reved it fir the first time! Engine kicked up to 3000 rpm, and wouldn't go down. I nearly freaked out until I realized my mistake.

Carb cleaner can de-ice your throttle linkage in cold weather. A little de-icer in a small squirt bottle can be useful too. The choke pull-off and return spring are easy to replace.

One thing you might consider is how much play your linkage has in the main air horn, or in the lower main throttle plates at the base of the carb. If there's too much play moisture can wick in between the rod and the body and freeze over night. Tight tolerances can make a difference here. You may need some bushings pressed in if it's an old carb.

[don t. - 72gmc]

It seems that I need a new accelerator pump spring. Not the one on the spring on the acc. pump shaft, but the one that pushes it back up, sits inside the carb body. If you press on the gas pedal, linkages push on a rod sticking out of the carb. This rod does not slide back up easily. When all is disconnected, everything else moves w/o a problem.

I did rebuild the carb last year, never noticed a problem til yesterday morning. I took it all apart, replaced the acc. pump assemb. w/the old part, works fine. The new acc. pump assemb. is tight inside the carb, especially on a full pump. On a full pump it was s-l-o-w comming back up. I would think that this "tightness" is normal for a new part. I would also "think" that the return spring prolly needs to be replaced.

Thanks....don t. ....

[Blue Beard]

I had a similar problem, mine being with and electric choke.

Friend of mine helped to adjust that and carb mixture. Ran much better after that and a few miles.

Blue Beard