CIS High Idle
 

My 74 2.7 has a very high idle now. The engine fires up fine and runs around 2500 rpm, then settles down to about 2000 rpm when warm.

The idle adjustment screw on the throttle linkage is backed all the way down, so it is not that simple.

(My vacuum advance is not connected, and I understand it not should be, right?)

Any suggestions to troubleshoot this? I suspect I have a vacuum leak, but I am a bit stumped.:(

Idle mixture, timing, anyone...?

its probably your AAV stuck open

Jason,

I'm new to the board, but have been reading it for quite a while. I've read a long thread you started on a high and erratic idle on your SC. I am having the exact symptoms you described. It seems you solved your problem by cleaning the AAV contacts (??). I'm not sure if PBH's '74 would be the same setup (or the same problem, for that matter), but I am curious about the resolution of your high idle problem.

Thanks,

Joe

had the same problem with my 74. tried everything with no joy. sensor plate was riding too high. the plate spring clip had slipped off. replaced clip, everything good again.

PBH, You don't have an AAV.

If you've got the idle adjustment screw tightened all the way and the idle is still high, then it could be the decel valve (3" bell shaped device on the left side with three vacuum lines running to it.). Test by plugging the lines.

It could be that your throttle is not closing all the way. Put your foot under the gas pedal and pull up. If the idle slows, lube the linkage.

You might have a vacuum leak.

Doug
75 911S

One last thing, vacuum advance: should I connect it or plug it?

Seems to have been a combination of mixture and timing, I got it down to 900 last night, I will double check today. Thanks for your help.