I've got a problem with an extremely high idle (or possibly stuck throttle). It idles at about 3500rpm!

Stock 12A engine.

If the engine is cold, I start it normally with the choke, push the choke in half way and it drops to about 1500-2000rpm like it should. But after about 30sec - 1 min as the engine warms up the idle increases to over 3000rpm. Pushing the choke all the way in has no effect, but pulling it out all the way will increase it slightly. I took off the air cleaner and checked the choke and it seems to be operating normally, so I don't think thats the problem.

The idle stays over 3000rpm even after the engine has reached operatin temperature. And its powerfull enough to accelerate the car in 1st, 2nd & 3rd gear until it reaches 3000rpm. 4th & 5th if I don't touch the gas it will very slowly slow down, but if I push in the clutch the rpms jump back up.

It doesn't really seem like a stuck throttle because I can step on the gas and accelerate normally to 7000rpm and if I back off or push in the clutch it drops back down to 3000rpm.

If I go to the carb and manually push the throttle linkage closed it will drop down to 1200rpm and stay there (even if I rev up the engine, when I release it will drop back down to 1200rpm). However, as soon as I shut it off and turn it back on again (with or without the choke) its back up over 3000rpm.

It was running perfectly up until yesterday when this all started happening -- before that I hadn't driven it for a few days, but it used to idle nicely at 750 rpm.



Any ideas??

 

pull the cover off the airbox, and look directly down the barrels, check to see that the secondaries are closed, and the primaries also almost closed.

 

Yup, they are.

I think I found the problem, but I need some help with it. Just gonna take a few pics of it and post them in 2 mins

 

i just noticed your from Langley, i grew up in Abbotsford.

 

Cool. How come you moved out east?



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Ok, here's some pics of what I think is causing the problem. It looks like a little motor with a cable attached to the carb/throttle












1 - What is it?

2 - What does it do? (or should it do in my case...)

3 - And what would cause it to stop working properly?



After I start the car, if I pull the linkage out all the way (towards the carb) my idle will go down to 750rpm. But if I shut the engine off and turn it back on, it pulls the cable and the throttle goes up again.

There's a little green w/ red stripe wire coming from it. If I unplug this wire and start the car it does nothing and thus the idle stays at 750rpm.


I guess temporarily I could leave it unplugged, but I assume it has something to do with starting when cold, so I'd like to get it fixed.

 

thats your hot start relay, you can completly remove it, all it does is open the throttle a crack when your starting the motor hot. if you don't want to remove it pull the clip from the cable and pull the cable off the arm and see if it fixes the problem. i doubt thats you problem though, i don't think it has the capacity to open the throttle that much. you might have a vacuum leak from a cracked hose. take a look at the bigger hose on the passenger side (near the fire wall) it kindof dissappears under the black plastic shield, and goes up to the anti after burn valve attached to the carb. its known to crack at the bottom because of it's vicinity to the exhaust. if its not cracked, while the car is running spary WD40 on all the hoses, if the idle increses or changes, thats most likely the problem

yeah i moved out east, cause of my dads work, been living here for 7 years now. i still miss BC though it's way too flat here.

 

nevermind the vacuum leak stuff, i didn't see the writing on the bottom, just remove the whole hot start assist

 

lol, I was just about that say that.


Thanks for the info. I'll disconnect the wire and cable.

 

If unhooking the wire solves the issue, just leave it unplugged. I guess that is there for those not able to figure out to lightly open the throttle when starting the engine warm.

 

I removed mine completely and have had no issues. My advice is to remove it and throw it in a box in the attic. That worked great for me!

 

Good to know its not needed. But I'm too lazy to remove it, so all I've done is unplug it