HELP! Throttle stuck!

[dzwestwindsor]

I have a 71 C20 with a 350 and Quadrajet carb.

I've never driven it at wide open throttle, but today I let my friend drive the truck and he drove it around the block hard, and floored it a few times. Then, the throttle got stuck and now it idles at 3000 RPM!

The linkage seems to be fine- it's returning all the way and is responsive to the pedal. So where should I look now? What could be the problem? I'm thinking it's stuck somewhere because the truck doesn't get driven hard often and maybe today after the throttle opened up all the way something got stuck.

Any help or suggestions?

[JointTech]

sounds like the needle is stuck.
im not much help but I have a funny story.
I just dropped an engine and trans into my 75 blazer. I was with a friend in the car. All of a sudden the engine went to WOT. brakes hold but the tires are smoking. im a kid and sort of paniced. I suppose I could have shut off the engine or put it in park... i was worried if I went to neutral or park it would blow my motor.

Anyway my buddy jumps out and pops the hood and whacks the linkage and it calms down.
after we thought about it we had a good laugh. 4500 lbs truck, tires smoking and he gets in front of it to open the hood and fiddle with the linkage trusting my foot would hold on the brake.

still laugh about that.
it was ony about 20-30 seconds of total time of the incident but it felt like minutes.

talk about monkey butt.

[sKnNyPpY]

Broken return spring? There are usually two for safety.

[dzwestwindsor]

Hey guys, got it fixed. The secondary valves were stuck open so I just pushed them closed with a screw driver. How would i prevent this from happening again? Is it okay to spray WD40 down a carb? Seems like it just got stuck from not being in use very often.

@JointTech, funny story! You got a real friend there

[Bears63]

How dirty is the carb? A good cleaning with some actual carb cleaner probably wouldn't be a bad idea.

[FirstOwner69]

Don't use WD-40. Try spray carb cleaner... Gumout,etc.

[88fordf150]

Originally Posted by dzwestwindsor

I have a 71 C20 with a 350 and Quadrajet carb.

I've never driven it at wide open throttle, but today I let my friend drive the truck and he drove it around the block hard, and floored it a few times. Then, the throttle got stuck and now it idles at 3000 RPM!

The linkage seems to be fine- it's returning all the way and is responsive to the pedal. So where should I look now? What could be the problem? I'm thinking it's stuck somewhere because the truck doesn't get driven hard often and maybe today after the throttle opened up all the way something got stuck.

Any help or suggestions?

Note to self: Never let my buddy drive my truck.

[Fitz]

Originally Posted by 88fordf150

Note to self: Never let my buddy drive my truck.

Where my truck is concerned, I don't have any buddies.

[Fitz]

Originally Posted by dzwestwindsor

I have a 71 C20 with a 350 and Quadrajet carb.

I've never driven it at wide open throttle, but today I let my friend drive the truck and he drove it around the block hard, and floored it a few times. Then, the throttle got stuck and now it idles at 3000 RPM!

The linkage seems to be fine- it's returning all the way and is responsive to the pedal. So where should I look now? What could be the problem? I'm thinking it's stuck somewhere because the truck doesn't get driven hard often and maybe today after the throttle opened up all the way something got stuck.

Any help or suggestions?

Install a throttle stop.

[no1udknow]

Originally Posted by Fitz

Where my truck is concerned, I don't have any buddies.

Amen to that! I value my toys almost as important as my wife , and I wouldn't let anybody take her for a spin.

[69chevytrucker]

Originally Posted by 88fordf150

Note to self: Never let my buddy drive my truck.

x2

[69chevytrucker]

Originally Posted by no1udknow

Amen to that! I value my toys almost as important as my wife , and I wouldn't let anybody take her for a spin.

lol i seen a sign at a car show that said ( if you run your fingers over my truck i will run mine over your wife)

[dzwestwindsor]

Hey guys so when I went to start it up today, it idled at around 700ish rpm. However, after spraying carb cleaner and opening/ closing the choke by hand to clean everything, I go to start it again and now it idles at 1050 rpm, even up to 1400 rpm on one of the starts. I made sure the secondary valves were closed all the way, and they are. The idle kinda has impulses now and is not perfectly smooth as before. I backed out my idle speed adjuster all the way. But still idling high, around 1000 rpm.

I'm really clueless now.. Any suggestions?

[geezer#99]

Check the high idle screw. It's below the choke pull off.

[dzwestwindsor]

Originally Posted by geezer#99

Check the high idle screw. It's below the choke pull off.

Seems to be fine, I didn't touch it at all earlier so it's still in the same position as when it was running right.

I'm starting to think that it could be a vacuum leak, or something is wrong with the choke/high idle kickdown. But it's probably a vacuum leak issue, because it doesn't seem to run smooth either, and I smell gas. But I don't see any vacuum leaks, everything seems to be plugged off.

Can vacuum leaks cause high idle? This can't be an ignition issue right, cause the RPMs are higher than normal?

[geezer#99]

Plan B!!
Take a pic of your carb.
Might be something obvious we can see.

[dzwestwindsor]

I'll try to get some pictures in tomorrow.

But just a little more information, even with the primary choke open all the way, it still idles high. So not a choke problem I'm assuming? Does the choke mechanism keep the throttle open wider at high-idle? Or does it only just close of the choke valve and that's it?

[Sammy]

I have had this happen twice. Mine was the throttle plates just barely were catching on the intake holding it open only at certain times after warm and high speeds. My fix was to install a 1 inch carb spacer never had a problem again.

[88fordf150]

Originally Posted by dzwestwindsor

Seems to be fine, I didn't touch it at all earlier so it's still in the same position as when it was running right.

I'm starting to think that it could be a vacuum leak, or something is wrong with the choke/high idle kickdown. But it's probably a vacuum leak issue, because it doesn't seem to run smooth either, and I smell gas. But I don't see any vacuum leaks, everything seems to be plugged off.

Can vacuum leaks cause high idle? This can't be an ignition issue right, cause the RPMs are higher than normal?

Spray small squirts of starting fluid around your vacuum hoses and gaskets, if you have a leak anywhere the idle will raise when it finds it.

[dzwestwindsor]

I just waited a night and everything was back to normal. Not really positive what was wrong...

Originally Posted by Sammy

I have had this happen twice. Mine was the throttle plates just barely were catching on the intake holding it open only at certain times after warm and high speeds. My fix was to install a 1 inch carb spacer never had a problem again.

How does the carb spacer work to help in this situation?

Originally Posted by 88fordf150

Spray small squirts of starting fluid around your vacuum hoses and gaskets, if you have a leak anywhere the idle will raise when it finds it.

Thanks for the suggestion, I'll keep the tip in mind.

[Sammy]

Since installing it the throttle plates on the carb no longer can make contact. To check if this is your problem..after the engine is good n warm..remove the air cleaner operate the linkage fully open n release allowing the spring to pull the throttle closed. Watch the plates from the top of the carb n see if they fully retract with out binding or hanging. Also check the 4 securing nuts for tightness allowing the carb to slightly shift.