What is normal hot idle speed for a 1987 C4?
Any one know?

Tanks

 

my 86 idles at 600-800 when warmed up, it used to surge up to 1500 and make this big Hissing noise when I hit the brake, but that only happens every now and agian, im sure that will be another story

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My '86 Cast Iron L98 idles between 800-900. Now and then, I have to tap the accelerator to get it to drop down from 1200-1300 though. Hasn't happened since spraying the throttle linkage with good ol' WD-40.

 

Base idle is set with a torx head screw on throttle plate, but do not use that for setting normal idle speed as that is controlled by computer via idle control motor. Spanner, your hissing noise you are hearing might be the brake booster, which if the diaphragm is leaking will cause an idle surge. [8D]

 

hmmm, yeah I knew it had to be some brake prob the servo or something, will this just go out one day leaving me on the side of the road? In other words should I go ahead and fix it?

 

When it goes out, you will notice no power assist on your brakes. Won't leave you, but sure will make it hell stopping at a fast speed. [8D]

 

my 87 idles at 600rpm.

 

Could be your Idle Control motor, need to clean throttle plates periodically for carbon buildup.

 

My '87 work-in-progress idles at 600

 

where and how do you clean the idle control motor, mech ??? My 84 has had all the pollution taken off except for the air pump and she starts at around 2000 and slowly winds down to around 900 after a couple of minutes.