1981 250/2WD/4-Speed idle issue

[myascape]

Hi all-

I'm chasing down some POSTs (Previous Owner Stupid Tricks) on my pickup, and have come across a doozie. I have replaced all of my vacuum hoses and double checked my wiring diagrams to make sure everything is where it's supposed to be. I even timed it to 10 deg. BTDC.

I can't get my idle to come down within specs, and suspect there's an air leak somewhere.

There's a stray sensor on my air breather without a wire going to it...it's a temperature switch with a button-type connector on it. It has three ports on it that go to the temp switch under the breather and heater trap. What is this, and what color is the wire that goes to it? I've gutted my wire looms and can't figure it out.

Help!

Joe in Norwalk, IA

 

[vwnate1]

Carby Idle

O-Kay ;

Your truck has the later model Rochester _aluminum_ MonoJet carby , it's pretty good and most have two electric idle solenoids ~ one is big and fat and is turned complete with the wire _disconnected_ to set the low speed idle to 400 ~ 600 RPMs, this prevents dieseling . then , you re-connect it's wire and use a tiny (like 3/16"" IIRC) Allen hex key in the center of it , to set the actual idle speed to 700 ~ 1,000 RPMs, engine hot .

The other idle solenoid ,is for cold warmup and the air charge sensor makes it come on until the intake air is above I forget what temp .

So , you need to look at both of these , one touches the choke's fast idle cam and the other is against the throttle lever proper , mine was twisted in as far as it could go and had no wire connected so my 292 I-6 idled poorly @ 1,300 RPM's when I bought it .

You can check for intake or carby vacuum leaks by spraying WD-40 or starting fluid here & there but never , EVER use Aerosol carby cleaner ! . it's death in a can and will attack your liver & kindneys . throw it away if you have any .

I hope this helps... maybe some one who can explain it better than I will chime in , there's lots of really talented folks here .

 

[The Carpenter]

high idle

i have been fighting an intermittent high idle on my 87 r10. i spent some time trying to track down what i was sure was a vacuum leak. i think there is at least a good chance that it may be a small leak at the back of the intake gasket. my truck got hot one time, and i will never forgive myself, but i've heard it's the back that gets the hottest.
i have no idea on the wires other than check the wiring schematic.

What about the flamable brake cleaner for checking vacuum leaks? (some aren't flamable)
yes? no?

 

[vwnate1]

Vacuum Leak Testing

Flammable is best ~ I like to use a snorkel to more closely pinpoint the leak .

For me , starting fluid works best be careful ! .