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Vacuum Gauge Specific Reading Help

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Thread replies: 14
Thread images: 1

>be me
>4 banger
>hook up vacuum gauge
>steady reading of 18 inhg at idle when it should be 21 inhg (yes i know the elevation math)
>open and close throttle quickly, drops to 15 inhg and back up to 18 inhg when it should be dropping to 0-3 inhg and back up
>looked all over diagnostics sites and can't find that specific reading anywhere
>Already tried advancing the timing on distributor, that didn't work
What could be causing this reading?
>>
>>17802511
what's an inhg?
>>
>>17802522
inches of mercury vacuum
>>
does it have any other symptoms? sounds just like not much ignition advance
>>
>>17802528
yes there are
when the choke kicks off, the car idles roughly and eventually stalls, also surges in rpms in idle
when not in idle (driving mode), no problems.
Also, I don't think the valves have been adjusted in over 20 years.
>>
>>17802540
also in idle, it does not want to stay at the normal 800 rpm's. whenever I give it gas, It drops below 800 rpm's and then stalls out.
>>
>>17802592
*let off the gas
>>
>>17802592
i would check the entire ignition. the advance, timing, strength of spark, everything.
>>
>>17802604
I already did, it's all good.
>>
>>17802540
Are you connected to manifold or ported vacuum? They will behave differently and you may be getting a false reading.

The idle dying when the choke comes off indicates lean running. Have you checked for intake vacuum leaks?
>>
>>17803132
This.
Also the iacv maybe?
>>
>>17803132
1. Manifold Vacuum
2. Yes I've checked for intake vacuum leaks and I have none.
I'm also thinking that the valves itself (not computer controlled) may attribute to it considering it hasn't been adjusted in over 20 years.
>>
>>17803154
I've already replaced the anti-dieseling(idle cut) solenoid and nothing.
>>
so there's nothing wrong with the ignition system, carburetor and no vacuum leaks (did the smoke test)
Thread posts: 14
Thread images: 1


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