idle???

porski · 03-23-2003, 06:35 AM

On my 79sc 3.0L,my idle when cold (first start up),goes from
550rpm-1200rpm,and gets a little better when warmed up.
I also recently installed new fuel injectors,spark plug wires,spark plugs,cap+rotor,and a fuel filter, all OEM from dealer. I was thinking this problem may have something to do with the cold start valve?,or could this be ajusted.. Any help would be great
thanks a head of time.

1979 Porsche 911sc targa WB
1992 chevy blazer
1990 chevy camaro Z28

Jim Sims · 03-23-2003, 07:14 AM

Is it going back and forth between 550 and 1200 rpm? What does a little better mean? Once the engine is running the cold start valve usually doesn't cause any problems unless it is leaking. The cold start injector only operates while the starter is cranking. A leaking cold start valve will cause the mixture to be too rich which causes a rough idle; the roughness will get worse as the engine warms. Instead I would check the WUR (warm up regulator) pressures, AAR (auxilliary air regulator) and their electical connections and hoses. One needs a pressure gage rig to test the WUR pressures. Cheers, Jim

porski · 03-23-2003, 07:53 AM

a little better meaning 750rpm-1000rpm when warmed up to operating temp. Thanks for your help Jim.

Jim Sims · 03-23-2003, 08:07 AM

If you recently installed new fuel injectors then the mixture may need to be adjusted; a CO gas analyzer is needed to properly do this. Jim

stlrj · 01:28 PM

I it's hunting between 750 and 1000rpm, your mixture is too rich and needs to be leaned out.

Test it yourself by creating a vacuum leak by removing your oil tank cap and see how it stablizes your idle.

Joe