Honda Civic / Del Sol (1992 - 2000) EG/EH/EJ/EK/EM1 Discussion

Undetected vacuum leak

 
Old 06-09-2019, 08:16 AM
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Default Undetected vacuum leak

Iím not very familiar with the d series but I have d16y7 I just pulled to put new bearings in,I didnít remove the head or intake and now I have consistent idle at 4500 I traced all the vacuum lines I can see tighten the Im nuts, aside from the im gasket leaking I donít know what to do.
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Old 06-09-2019, 09:01 AM
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Default Re: Undetected vacuum leak

A faulty IACV can give the same behavior as a vacuum leak.

A bad brake booster can also cause a vacuum leak.
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Old 06-09-2019, 12:11 PM
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Default Re: Undetected vacuum leak

I didnít know the brake booster would interfere with it. Is there anything aside from swapping it out I can try
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Old 06-09-2019, 12:41 PM
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Default Re: Undetected vacuum leak

To test for a booster leak, remove the booster hose and block it off so air can't get into the engine. A properly working booster doesn't let any air flow when the brake pedal is not being pressed.

That much air kind of suggests the throttle plate isn't closing. Make sure the throttle cable is slack when not pressing the gas pedal. Pull on the throttle linkage to confirm it is all the way closed against the stop.

Other tests are to remove the intake pipe and cover the throttle body inlet. The engine should stall out. If it doesn't, air is getting in somewhere other than the throttle body. The throttle body has three ports before the throttle plate. One goes to the air adjust screw, one to the IACV, and one to the FITV. Only the first one should be sucking any air when "idling" at 4500 rpm. Block them off and see if speed changes.
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Old 06-09-2019, 04:23 PM
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Default Re: Undetected vacuum leak

This is a lot of help I will report back soon
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Old 06-09-2019, 06:44 PM
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Default Re: Undetected vacuum leak

Originally Posted by mk378 View Post
Other tests are to remove the intake pipe and cover the throttle body inlet. The engine should stall out. If it doesn't, air is getting in somewhere other than the throttle body. The throttle body has three ports before the throttle plate. One goes to the air adjust screw, one to the IACV, and one to the FITV. Only the first one should be sucking any air when "idling" at 4500 rpm. Block them off and see if speed changes.
OP mentioned it's a D16Y7 motor (OBD2 98-00). I believe the 6th gen cars didn't utilize an FITV so should only have 2 ports, IACV and Idle adjust screw port.
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