Fast Idle

[Gpaw44]

My 86 GMC truck is stuck on a fast idle now when I start it and it will not come off the fast idle. This happened several years ago and I took in to a mechanic. When I picked it up the next day he said he just disconnected and reconnected the cruise control and that stop it. Does anyone know what might be stuck on cruise control and what might be disconnect to make it come off a fast idle? Thanks in advance!

 

[MarineOne]

Disconnect the rod and work it in and out its probably sticky. A little lithium grease would help

 

[Ken B]

I have a fast idle start up with NO cruise control. I will look at throttle cable and see that its free, any other suggestions? No muffler right now so being a nice neighbor and letting people wake up naturally, not to a 350 with no muffler......

 

[Ken B]

SOrry 350cu T350 trans. all swapped in in the last year and never ran since really

 

[Ricko1966]

I have a fast idle start up with NO cruise control. I will look at throttle cable and see that its free, any other suggestions? No muffler right now so being a nice neighbor and letting people wake up naturally, not to a 350 with no muffler......

Your supposed to have a fast idle on cold start. After the engine warms up a few minutes you blip the throttle and it comes down. If yours doesn't do that there's many things that will make it idle too fast,first thing check hard for vacuum leaks, next make sure throttle linkage moves free and isn't hanging up. Next thing make sure you didn't crank the throttle stop screw in to make it idle. You need to get the idle down,time it correctly and set the carbureator. This may mean,backing the throttle stop screw way out and the fast idle screw way out. But you can't time it at fast Idle. Okay I take that back , you can time it, if you set it for total timing. Total timing is timing with,vacuum advance plugged and engine revved until distributor quits advancing then time it for 34* total. Total varies 28-36* depending mostly on what cylinder heads you are running 34-36* degrees is usually close for most heads. We can get into that more latter.

 

[Ken B]

Rick you are an encyclopedia of knowledge. I am checking for vacuum leaks 1st

 

[Ricko1966]

Rick you are an encyclopedia of knowledge. I am checking for vacuum leaks 1st

Thank you.Been around it my whole life,read 1969 motors auto repair manual cover to cover like a novel at 13( because dad got sick of answering questions,handed me the book and said this will answer everything)I read the whole thing. 1st no assist engine swap 14 years old,64 impala pulled the 327,bought a 70 caprice donor. Learned a ton,drive shaft lengths,spread bore vs. Qjet etc. 1st job as a tire boy,grunt in a shop a 15. Statute of limitations is over I was doing Inspections at 15 years old. I knew what passed,what to check and let the boss know,he passed them,failed tgem,decided what I could fix. You didn't want me inspecting your car I was thorough,didn't want to make a mistake. Still have that book,got it from dad decades later,because that book dictated most of my life.

 

[Ricko1966]

God that all brings back memories, 14-17 thought square bore AFBs ( now known as Edelbrock Performer) where the deal. Tore apart and modified my first Qjet at 17 and never looked back.WOW I'm having a moment! Yea I started off doing a lot of things I tell people don't do now,because I grew and I learned,and realized after time why somethings are the way they are,even when they don't make sense to us.

 

[Ken B]

well your passion for this stuff shows thru !
My 1st project started at 56years. My big brothers truck he gave me when I was too broke to afford a second car 40 years ago. Lost him 15 years ago but the truck stays with me forever.
actually just drove the truck for the 1st time in 4 years today. got the idle figured out( vacumn hose was missing) got lots of little things to tighten up and test out but its running and driving.
Paint and body.....later this year or spring with any luck!

 

[PrairieDrifter]

The number 1 high idle issue I've seen is incorrect choke adjustment. If the choke doesn't come all the way off it'll hold the carb on the high idle cam.

This will also cause many bad tuning setups, timing and carb. Because people think it's idling too high they crank everything down, then everything is out of wack. Then it comes off the high idle cam one day and won't run for ****

 

[Ken B]

makes sense.