1980 SC lumpy idle plus
 

My 1980 SC had a top-end rebuild, re-ring, reseal, SSI's installed with Flowmaster muffler and runs great. The idle is not really smooth and it sometimes sputters on up-shift below 3000 RPM. But what is most annoying is the gargeling and spitting when coasting in any gear. Aside from tweaking the mixture some more, what gives? This is a standard 3 liter CIS with vacuum advance/retard on the distibutor and SC cams. There is no more CAT or OX sensor and it runs on 5 degrees BTDC. Very good at anything above 3500, really wants to go. Has anyone had similar experience with sputtering below 3000 and lumpy idle plus this aweful ruccus when coasting? Thanx anyone.:confused:

got yer frequency valve workin? it has to function. disconnect the computer relay under the right seat. if the idle doesn't change, that's the problem.

Thanks John: I'll try your suggestion and I noticed the relay under the seat, but where is this frequency valve you are refering to?:eek:

the frequency valve is in front of, and below the sensor plate housing. it looks like an electric injector with a black snap on plug. it makes a distinct buzz/rattle when it is working. they don't fail much, it's usually something else upstream. if the idle falls off when the relay is unplugged, you don't have to worry about it.