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> High idle problem, Hunting
Flyinlow
post Mar 31 2026, 05:39 PM
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Nearing the end of my restoration drove car today for first time in 30 years!! Start up is 1000 rpm a little high…. Then on its own goes to 3000 rpm then seems to settle to 2500 rpm.. when shifting rpm rises? I checked throttle cable for routing… all good and it did decel but not quickly as it seemed to be hunting any help much appreciated.TIA Dennis (IMG:style_emoticons/default/blink.gif)
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Flyinlow
post Mar 31 2026, 05:44 PM
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Car is 74 2.0 D jet and I had no response from idle adjustment screw
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emerygt350
post Mar 31 2026, 05:49 PM
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If you just start the car and let it sit, what does it do? Cold or hot?
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mgphoto
post Mar 31 2026, 05:53 PM
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Big air leak in the intake.
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Flyinlow
post Mar 31 2026, 06:14 PM
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QUOTE(emerygt350 @ Mar 31 2026, 04:49 PM) *

If you just start the car and let it sit, what does it do? Cold or hot?

Hot then idle goes wacky
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Flyinlow
post Mar 31 2026, 06:16 PM
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QUOTE(mgphoto @ Mar 31 2026, 04:53 PM) *

Big air leak in the intake.

How would you determine that?
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mgphoto
post Mar 31 2026, 08:37 PM
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If it changes when it gets hot must be something with the AAR, Auxiliary Air Regulator, for cold weather starting.
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mgphoto
post Mar 31 2026, 08:41 PM
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If the idle undulates, it usually is the idle air screw out too far, but you said screwing it in made no difference.
The next possibility would be an air leak.
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porschetub
post Mar 31 2026, 11:54 PM
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QUOTE(mgphoto @ Apr 1 2026, 12:53 PM) *

Big air leak in the intake.

Certainly sounds like it, quick test on the throttle cable ,when the engine is up to temp disconnect it and see what it does .
The vacuum leak is a telltale of loose /leaking air hose/s or many other reasons ,D-jet isn't happy with air leaks ,even a small leak will render the air screw to no non -op .
Go back and check everything ,cheers.
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Geezer914
post Apr 1 2026, 03:59 AM
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Do a smoke test to find the air leak.
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rfinegan
post Apr 1 2026, 05:50 AM
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Disconnect and plug the vacuum Lines to AAR and the decal valve and confirm your Idle settings.
Also just a few degrees to much on your timing will give you a high idle too.
A visual inspection for vacuum leaks or a smoker(cheep on amazon )will help pinpoint any vacuum leaks
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