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blue62 · 08-09-2021, 11:35 AM

It would be best to just put the vacuum gauge directly into the intake vacuum port and plug the check valve off.
So NO TEE fitting just what ever you need to hook the gauge directly to the intake. If you need a length of hose between the gauge and the intake so you can sit in the car and work the throttle and watch the RPM thats fine.

With that check valve (which connects to the EVAP system) connected and involved in the test there is the possibility that the EVAP system could run it's test while your trying to do the exhaust restriction test.

What happens is that the DME/ECU sends a signal that puts the entire EVAP system under vacuum then checks for leaks over a period of time.
So it draws on vacuum from the intake. If that happens at the same time your holding RPM at 2000 and watching the needle the needle is going to slowly drop just like an exhaust restriction.
So you could get conflicting results.
hope that makes sense.

You may throw EVAP codes or other codes because the EVAP vacuum line it is unplugged during the test.
If you do just clear them after you done testing.

08-09-2021, 11:35 AM	#49
blue62 Registered User Join Date: Aug 2018 Location: Woodland Wa Posts: 1,309	It would be best to just put the vacuum gauge directly into the intake vacuum port and plug the check valve off. So NO TEE fitting just what ever you need to hook the gauge directly to the intake. If you need a length of hose between the gauge and the intake so you can sit in the car and work the throttle and watch the RPM thats fine. With that check valve (which connects to the EVAP system) connected and involved in the test there is the possibility that the EVAP system could run it's test while your trying to do the exhaust restriction test. What happens is that the DME/ECU sends a signal that puts the entire EVAP system under vacuum then checks for leaks over a period of time. So it draws on vacuum from the intake. If that happens at the same time your holding RPM at 2000 and watching the needle the needle is going to slowly drop just like an exhaust restriction. So you could get conflicting results. hope that makes sense. You may throw EVAP codes or other codes because the EVAP vacuum line it is unplugged during the test. If you do just clear them after you done testing. Last edited by blue62; 08-09-2021 at 11:46 AM.