EGR system - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 3 (permalink) Old Dec 21st, 02, 01:07 PM Thread Starter
Senior Tech
Join Date: Dec 2001
Location: ocala, FL
Posts: 210
could someone please explain to me how the egr system opens and closes. i know its function. i asked over at and the guy told me that as rpm's increase, vaccum increases pulling the valve open. i thought that the vaccum decreased as rpm's increased. any help would be appreciated.
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post #2 of 3 (permalink) Old Dec 22nd, 02, 07:53 AM
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Join Date: Nov 2001
Location: Oxford Pa.
Posts: 503
There are 2 sources for vacuum...

Manifold vacuum, which is the vacuum BELOW the throttle plates and will drop when the plates are opened...

Ported vacuum, which is a vacuum port ABOVE the throttle plates and will have an increase in vacuum as the plates are opened...
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post #3 of 3 (permalink) Old Dec 26th, 02, 03:41 AM
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Join Date: May 2000
Location: Westlake, OH 44145
Posts: 707
Nate the way you EGR system operayes differs based on model and year. But I can summarize like this. Manifold vac will drop dependant upon engine load. as engine load is decreased maifold vac will return. Ported Vac is above the throttle plates as stated and can never be more than manifold Vac. It is a type of timed vac. Egr valves are opened by either ported vac or a solenoid using ported or manifold Vac. and sometimes in conjunction with exhaust backpressure.

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