Question 2, High Idle - yet again Options

[BenNC]

I know, there have been a gazillion posts about high idle. Most of them seem to end with check al the hoses and set the timing.

I have replaced all the hoses, and set the timing. With the idle adjust screw all the way clockwise I idle at about 1800 rpm. Per my Haynes manual, turning the screw counterclockwise whould lower the speed, butthe idle increases for me. Is this an error in the book, and what should I look at next.

By the way. It idled fine until the points of undetermined age froze on me. It idled fast with new points and has continued with the new Pertronix.

Thanks

[mightyohm]

Clockwise should reduce the idle speed. You're screwing in the bypass screw and making the bypass passage smaller.

For the first few minutes the engine is running the AAR will be letting extra air in and raising the idle. You can block the input to the AAR to check this.

Check to make sure the throttle plate is closing all the way also. If not that will let air in too.

You should be able to stall the engine by screwing the idle screw in all the way and plugging the AAR.

[Dave_Darling]

Which idle adjust are you turning? The one on the ECU (the FI's "brain box") sets the idle mixture, not the idle speed. Though having the mixture incorrect can affect the idle speed...

If you screw in the screw on the throttle body, the idle should drop.

Sounds to me like you either have a vacuum leak or your ignition timing is over-advanced. Since this behavior started when you changed out your points, I would guess it's the latter. Try turning the distributor until your idle gets back to where it was before your old points froze up on you. Betcha that gets the timing pretty close.... I've set my timing that way (just to approximate it after pulling the distributor out) and wound up being dead-on when I checked with the timing light...

--DD

[BenNC]

I'm putzing with the screw on the throttle body. At this time it is all the way in, and the motor came like that.

I'll check the AAR when I get home.

Aside from hoses where are my other likely leaks?

I agree Dave. I don't think that it is a coincidence that the problems cropped up right after the points change. I give that a shot to.

[Bleyseng]

If the screw on the throttle body doesn't slow it down:
1. AAR valve stuck open
2. Vacuum leaks or misplaced hose
3. Vacuum retard hose is not set up right
4. Timing way advanced
Plug AAR hose first.
Warm up car, disconnect and plug the hoses to the dizzy. Set the timing to 27 degrees BTDC. Hook up dizzy hoses, idle should drop. Reset idle with the AIR BYPASS screw on the throttle body and set mix on the ECU.
If its still high check for leaks with small amounts of starting fluid spray.

Geoff

[mightyohm]

Did you retime the engine after you changed the points?

You really have to, like Dave says that has a big effect.

[BenNC]

Timing was set after adding the Pertronix. The new points were only in the car for a couple of days.


You guys will teach me to post two questions at once.

[Bleyseng]

Likely leaks?
injector seals
throttle body to plenum seal
MPS hose
PVC hose if you still have the weird rubber y fitting that the the decel and PVC hose go to.
PVC rubber elbow at the oil filler
the plenum-it will split or crack
Throttle body at the throttle shaft- steel on aluminun slowly wears until its sloppy and leaks. Can be bushed with a brass bushing and makes for smooth throttle petal
The big plenum to manifolds hoses
Manifold to head gaskets
Check each area with a small shot of starting fluid, [B][/B]small shot[B], otherwise you will flood the engine compartment with starting fluid and the engine will rev up because of that not what you are testing.
If there is a leak say at the #3 injector seal, when you spray it the engine rpms will go up at few hundred. AH HA! a leak!

Thats how you can track this down.

One other thing, unstable idle is a problem with a wornout distributor. Pull the dizzy and check to see if there is ANY side to side slop of the shaft. If there is, get a rebuild one as you will chase idle problems forever.

Geoff