Accelerating on its own/General K5 Education Advice

[EvG]

Hello, I am very much a newbie when it comes to maintaining my own vehicle (and when it comes to online forums). I have a 1973 K5 and have been relying on my auto shop for every little thing. They do a good job, but it is expensive and a hassle to take the truck in every time something goes wrong. I would like to learn more and be able to maintain my vehicle myself more. I will research these forums for specific issues, but would also love advice on other places to find good education on my vehicle. TIA!

For this issue - I could not find a thread on this topic from my rudimentary search terms. The other day when driving home on a cold evening, I flipped my heater on while on the highway and the truck seemed to start accelerating on its own. When I slowed down, I was confirmed, the throttle seemed to be wide open. The pedal was not stuck down, but the throttle was wide open. I was able to safely park the truck at home, but when I restarted it, the throttle was again wide open.

Is this an issue I could tackle on my own? What info do ya'll need to help? Thanks for any help ya'll can give.

 

[tRustyK5]

For K5 knowledge, and general mechanical knowledge you're going to be hard pressed to find more relevant content in any other place. Stick around, read lots, and ask all the questions you like. I think you'll find the response are good and usually in "almost real time". This is a very active site, with lots of really knowledgeable people.

I am going to suggest that your truck was not at wide open throttle, if it was you wouldn't have been able to hold it back with the brakes. I'm going to guess it's stuck on the fast idle cam on your carb. This can lead to "no load" engine speeds well over two thousand rpm, which sounds worse than it is. If you can, snap a few close up pictures of the driver's side of the carb from a few slightly different angles with the air cleaner off. I'm betting we'll see the high idle cam engaged. You'll probably have to double check you have 12 volts to the electric choke when the engine is running, maybe have to clean and lube the choke linkages, and finally get your choke adjusted properly so the high idle doesn't engage when the engine is warm again. Carbs suck, but with some patience can be made to be acceptable even by a novice.

 

[EvG]

Here are a couple of shots of the carb.

 

[diesel4me]

I don't see a throttle return spring...usually GM had a pair of springs,one inside the other,that went to the same lever the throttle cable is on,and anchored to the intake or thermostat housing..yours may be different depending on the year..

 

[skunked]

you can see the throttle return spring came off, see the last pic.

 

[diesel4me]

I cant see the spring.. I'll take your word for it...

 

[skunked]

I cant see the spring..View attachment 250014 I'll take your word for it...

for the blind, see the red circle

 

[Abusfullofnuns]

It was so obvious I couldn't see it either. That spring has been sprung.

That was worth the $25 to post pictures, eh?

 

[jeff in co]

Does it need a new gasket bottom of the carb too?

 

[tRustyK5]

the part of the gasket we can see is definitely looking like it is torn. Whether it's cheating air is another thing...

Pictures > a thousand words

CK5, still with the cheapest diagnostic fee around.

 

[campfire]

So has the spring been replaced yet?

@EvG

 

[EvG]

Hello all! Thank you for your help! I had to get the spring ordered as it wasn't in stock at the shops I tried.

But YES! Once replaced all is well. I did get a variety of springs and I think the one I chose might be a bit too stiff/tight as now the accelerator takes a great deal of pressure to depress. I may swap the spring for another one from the kit, but that was definitely the issue.

Thanks again! I'm sure you'll all get my next obvious question soon...
EvG

 

[JoshHefnerX]

A little late to this but you probably want to have 2 springs on it as mentioned earlier 1 inside the other - incase one spring goes away, as you've had happen...

 

[EvG]

A little late to this but you probably want to have 2 springs on it as mentioned earlier 1 inside the other - incase one spring goes away, as you've had happen...

Thanks! I did exactly that.