250 high idle troubleshoot. Please help!!!

[81square]

I have an 81 k10 250 i6 that I believe has the integrated head. The idle on it is VERY high and it sucks gas like no other. Sometimes when I start it the idle is a little lower and it sounds much better, but once I hit the gas and let off the idle goes back up. I'm thinking maybe the Choke is stuck? Just put a new carburetor on it a year to a year and a half ago and I don't get what the problem is. The Idle is only really high in Park or Neutral, when I put it in to drive or reverse the idle goes way down, but sometimes after I hit the gas once I let off it goes up slightly again. There is also a decent amount of slack in the throttle cable.. Maybe too much? Please help!!!!

[geezer#99]

Nice pic of your truck but maybe a pic of your motor so we can see the carb might help more.

[81square]

Originally Posted by geezer#99

Nice pic of your truck but maybe a pic of your motor so we can see the carb might help more.

I don't have a pic of my motor handy. What do you need to see?

[geezer#99]

The motor!
With the air cleaner off.
With no pic we're just guessing.
Might be something obvious.

[rwhit57]

It could be several things. Does it have a decent spring that holds it all the way back. Start there then look at choke. Spray some cleaner and lube around it. Make sure the cable isn't binding somehow,they have a plastic sheath that sometimes wears. Get some one to operate the pedal while you watch with the motor off, maybe you'll see it. There's a few things.

[nonstop]

Also check your advance mechanism. Make sure it is returning and not binding.

[81square]

Originally Posted by nonstop

Also check your advance mechanism. Make sure it is returning and not binding.

Originally Posted by rwhit57

It could be several things. Does it have a decent spring that holds it all the way back. Start there then look at choke. Spray some cleaner and lube around it. Make sure the cable isn't binding somehow,they have a plastic sheath that sometimes wears. Get some one to operate the pedal while you watch with the motor off, maybe you'll see it. There's a few things.

[QUOTE=geezer#99;7909353]The motor!
With the air cleaner off.
With no pic we're just guessing.
Might be something obvious.

Thanks for the info guys! here is a few pics of the motor and carb. Only reason the hole on top of valve cover is exposed is cause I took the aircleaner off.

[geezer#99]

Nice clean carb.
Your choke is adjustable. That black cap on the front can be rotated to a leaner setting. I can't tell if the cap is held on with screws or not. Just loosen them slightly and the cap should turn. Should be some marks on it. If not make your own in case you want to put it back where it was.
Do you know what your timing is set at?

[D13]

My initial guess would be lack of return spring, sticking choke, or worn throttle bushings although a 'proper' carb rebuild should have fixed that. They may also have turned up the idle to hide issues and turn up the fuel to compensate for vacuum leaks. If they turned it up too much and didn't adjust the linkage properly then the choke may stick on or off when it shouldn't. Integrated heads are notorious for vacuum leaks. There are miles of vac hoses and the head itself likes to crake or warp. Two favorite tests. Cap / plug all the factory vacuum attachments on the engine and carb and evaluate. If no change, reconnect. spray SMALL amounts of carb cleaner around the base of the carb, and on the intake runners (small amounts so if it catches fire it goes out quick).

[Joe Z]

I have 2 of those motor in my stick c10. I had a issue with the hight idle before and I can't remember what was the cause of it but I replaced all the vacuum lines, distributor components, and a tone of other parts. All you can really do is just check it one piece at a time. Start with the obvious culprits first and it's usually a good idea to have an friend help. I'd start with the throttle cable. Might be sticking on return.
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