K5 starts fine but stalls in drive or reverse

[Daners]

Hey guys,

I'm a new K5 owner and recently bought a 1984 K5. The truck starts great, idles well but stalls when I put it in drive or reverse and give it a little gas. After I warm it up for a while and drive it for ten or fifteen minutes it doesn't stall but still hesitates from a stop once I step on the gas.

I brought it to a mechanic to get it ready for smogging, he cleaned out the manifold and checked the fuel system. He said everything checked out fine. I've been doing a little research and haven't been able to find anything that fits this problem exactly. I have made no modifications to the truck since I bought it except putting cats on it, it made no noticeable difference to how it ran.

The carb is pretty small (not the original) and I have a Holley 4bbl carb I can put on it. However, before I do that, I want to make sure it isn't something else. One problem at a time.

It also looks like I've got a bad freeze plug and cracked rear engine seal. Again, one problem at a time.

Any help identifying the stalling issue would be appreciated.

 

[Deuling]

Could it be something with the torque converter/tranny? Like its locking up right away and the engine just stalls? I have no Idea just sounds like a tranny problem to me...

 

[paratrooper307]

Could also be a choke not working properly. When the truck is cold it needs more gas. When you put it in gear it lowers the RPM and can stall out if the choke doesn't compensate. When the engine is warm you don't need the choke and it isn't an issue. Mine did this same thing until I replaced the choke on my quadrajet. The hesitation could be a timing issue or a weak distributor or fuel pump.

 

[shady]

Vacuum leak. thats exactly what mine was doing and I found that the vac ball on drivers side firewall was leaking. disconnected it plugged line and it runs good now.

 

[Deuling]

Vacuum leak. thats exactly what mine was doing and I found that the vac ball on drivers side firewall was leaking. disconnected it plugged line and it runs good now.

Good call, I did the same on my van.

 

[K85 Octane]

Do you have access to a timing light?

What is the carb? Get us some identification labels from it and we can go from there.

Carb
vacuum
timing

even if two cylinders were dead (nvm the bad idle), it could still move itself, so spark plugs and their wires...meh

 

[Daners]

My money is on the vacuum leak. As soon as the rain stops here I will check it out.

It's not the timing because it idles fine, accelerates, and there is no shaking or vibrations when the engine is running. It's only when I accelerate from a stop when the truck has been running less than 15 minutes or so and it gets better as the truck warms up.

If their is no vacuum leak, i'll check out the choke.

Thanks guys.