I just bought a 1982 econoline e150 with a 300 inline 6 that ran fine but it needed a head gasket replaced.

Last night I tore it down, replaced the gasket and put it back together, but when i went to drive it today it will idle fine until it warms up and the choke turns off. then it surges down to probably 300 rpm, nearly dies, and then comes back up near 1000 repetitively. the only thing that stops it from surging is giving it throttle.

Checked my vacuum lines for cracks with no luck,
I dont have any idea how much of this van would be computer controlled but I was thinking I might have to retorque the intake manifold or it might have air in the coolant lines.

Anybody have any ideas?

 

Hi Renotay,

The 82 doesn't have ANY computers at all. It should be the duraspark ignition system, which has an ignition control module on the driver's side fender, and the rest is controlled by vacuum.

It sounds like you have an air leak somewhere. Possibly a brittle gasket cracked while you were working on it? Did you remove the carburetor or anything during the procedure?

Those color coded vacuum lines (if you still have the originals) generally get filled with hairline cracks which are difficult to see. Enough of the cracks can cause a problem. This is usually remedied by replacing all of the vacuum lines with new, fresh rubber ones.

Lastly, the exhaust manifolds are known to warp after many years of use. If you removed yours, it's possible it "relaxed" when you pulled it off and is now too warped to put back on correctly. If this is the case, you won't be able to retorque it enough and you'll need to take the intake/exhaust manifold down and have them planed. (This is usually less expensive if you leave them bolted together. Change out the gasket between then when you're done.)


As for checking the choke, if the choke is mostly closed (about 1/8" open) when the engine's cold, and straight up and down when it's warmed up, your choke is working fine.