[FIXED] Really, REALLY high idle problem

[danzo620]

So yesterday morning I get in my truck to go to work. Start's up fine, I throw it in reverse and start backing out. Then when I put the clutch in, it revs to 3500 rpm and stays there. Now it won't idle lower than that.

I checked the choke heater and sprayed some carb cleaner while moving the fast idle cam to make sure it didn't somehow get stuck. I tried looking up other threads to see if people have had this issue and what to do about it. Datzenmike mentioned checking the voltage and when the truck is off I get a 12v reading on the choke heater, but when the truck is on I get nothin. I'm not great with electric shit so maybe I'm not doin that part right.

When the engine gets to temp (which is pretty freakin fast sitting there idling at 3500) the choke is open. And when I turn it off, it diesels like a mofo for a few seconds. So, if anyone has any suggestions or knows what I can do to fix this, I would really appreciate it. It's a '76.

Thanks, guys.

[datzenmike]

To be revved up like that, air and gas must be getting in somewhere.

 

 

Check that the throttle cable is properly seated on the rotating part of the carb.

Check that the throttle cable is returning to idle and is not sticking.

 

Look down the secondary throttle with a fleshlight. Is the butterfly completely closed? What about the primary? Is there something stuck in it?

[metalmonkey47]

Is the choke opening all the way when warm? If not, then the fast idle cam isn't releasing.

[KlassicMotion]

Look down the secondary throttle with a fleshlight. Is the butterfly completely closed? What about the primary? Is there something stuck in it?

 

Did you buy one of those?

[danzo620]

The choke is open all the way when warm

 

And the throttle cable is properly seated on the rotating part of the carb.

 

I'll try and jam my fleshlight down in the carb, but I don't know how much that'll help, mike.

 

I'm gonna go run and make sure somethin didn't get stuck in it right now.

[datzenmike]

Did you buy one of those?

fucking auto correct....

[laotsu]

fucking auto correct....

auto-correct says volumes aboot the users vocabulary D-Mike... volumes. :rofl:

[danzo620]

Ok,

 

It was hard to see down in to the carb but it looks like there was something holding it open just a little bit, I don't think it's enough to have it idle so high but I took some oics.

 

Throttle cable looks properly seated and felt like it was returning all the way.

 

 

[datzenmike]

 

Looks like something jammed in there on the left holding the secondary open. Bet that's it. If driving, don't hammer it hard enough to open the secondaries or it may dislodge and get sucked into the motor.

[danzo620]

Alright, so I just got home from work and got back in there.

 

Here's what I pulled out of the carb.

 

Thank god that shit was magnetic.

Here's the other side of it

 

Any ideas what that little piece of metal might be?

I'm hesitant to go start up the truck and see if it runs in case that piece of metal actually belonged somewhere.

 

While I was pulling that out, I noticed some weird marks on the side of my carb.

 

That rectangle cut out on the side looks like it has been recently damaged a bit. Don't know how that could've happened.

[GRpufnstuf]

Wow that's a big weird hole.

 

I'm guessing that metal piece might be from the air cleaner? Maybe a piece of the temp sensor that opens the preheat tube?

 

That cutout 'hole' doesn't look as chipped up in your fleshlight, down the barrel pic. Did it get chipped while you were working at it?

 

I'm pulling my carb today to look for air gaps and leaky spots. I'll look for similar parts that are hopefully still in place

[datzenmike]

Well that's probably it. There's a thermostatically controlled warm air valve and a separate temp sensor that could have come apart. It's inside the air filter and free to go directly into the carb. Maybe have a look at it.

[danzo620]

Wow that's a big weird hole.

I'm guessing that metal piece might be from the air cleaner? Maybe a piece of the temp sensor that opens the preheat tube?

That cutout 'hole' doesn't look as chipped up in your fleshlight, down the barrel pic. Did it get chipped while you were working at it?

I'm pulling my carb today to look for air gaps and leaky spots. I'll look for similar parts that are hopefully still in place

  

 

That's a good point. I probably did that somehow jamming my fleshlight in there and didn't realize it. Good catch.

 

 

Well that's probably it. There's a thermostatically controlled warm air valve and a separate temp sensor that could have come apart. It's inside the air filter and free to go directly into the carb. Maybe have a look at it.

Sounds like you guys might have this figured out. I looked around in the air filter after I pulled that piece out but didn't see where it came from. I'll go check it out again here in a minute.

 

Thanks guys.

[GRpufnstuf]

Grabbed a pic of the parts I was talking about in the air cleaner while I was under my hood today

 

 

'76 probably looks different or maybe there's more?

 

ALSO, if you have the same amount of pine needles under your air cleaner... That might be your problem!

[datzenmike]

Look just under that black plastic cover on the far side. Just to the left of that hole? Does that look familiar????

 

 

 

 

The black thing is the temp sensor and opens and closes the vacuum door in the air filter's snorkel to mix cold and manifold heated air.

[danzo620]

FIXED IT!!!

 

I'm glad I waited to fire it up again after getting that piece out because when I went back I saw a little gasket from the small venturi sitting there on the butterfly that had the piece of metal jammed in it. So after FINALLY getting that little bastard out, I noticed on the primary venturi that there was a similar looking piece of metal that's acting like a shim on the backside to keep it in place. In the pic, it's the little piece sticking out that I'm trying to point to with the screwdriver.

 

 

So after getting that shit back together and in there properly, the truck runs better than it has in a loooong time. So obviously this was an ongoing problem that I had been missing. No more dieseling when I shut it off, steady idle once I got that tuned back in after fucking with it trying to lower it when it was crazy high, smooth acceleration. SUCH a relief. 

 

So thanks for the help guys, problem solved!

[danzo620]

Is there a way to edit the title so it says [FIXED] or something like that?

[laotsu]

use full editor

[danzo620]

Word

Thanks

[datzenmike]

Take a look on the back side of the carb near where the missing piece fell out. There should be a fastener that locks the venturi in place... maybe a screw?. If loose this may fall out again. California carbs are non removable venturi.