How much vacuum should it have?...

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May 30, 2003 | 08:21 AM

RPO-B4Z

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Joined: Aug 1999

Posts: 30

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From: St. Charles , MO

Car: 1989 IROC-Z 72Kmi.

Engine: L98

Transmission: 700R4

Axle/Gears: 2.77 aussie 9 bolt

How much vacuum should it have?...

How much vacuum should I be seeing while the car is idling. I am taking the reading off of the port that supplies vacuum to the fuel pressure regulator. I'm getting maybe 14Hg. My car is shuddering (worst at 1500rpm). Can't pinpoint the cause.
It's an 89 IROC L98.
Thanks

May 30, 2003 | 11:38 AM

Viprklr

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iTrader: (5)

Joined: Feb 2002

Posts: 3,462

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From: N. Illinois

Car: 92 GTA/ 00 TA

Engine: 383/350

Transmission: 700R4/T-56

Not sure what the magic number is but I get 17 with the stock cam. 92 L98

May 30, 2003 | 12:04 PM

CamaroX84

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Joined: Sep 2000

Posts: 1,230

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From: Michigan

Try taking the reading from a different spot. Now I'm not sure if this applies at idle or not, but you may need the vacuum for the fuel pressure regulator to be working to it's fullest effect and to get a proper vac reading.