Thread: Back pressure
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Old 02-11-2013, 08:21 AM   #7 (permalink)
Runs with scissors
Join Date: Jan 2013
Location: Illinois
Posts: 89

Spot - '05 Scion XA
90 day: 30.33 mpg (US)
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It's a pretty simple to check for exhaust restriction. Remove an upstream O2 sensor and screw a 5/8" spark plug adapter from a compression tester into the bung. Connect a vacuum gauge that also reads positive pressure to the adapter. Fire up the engine and observe the gauge. Less than 4" of positive pressure = a serviceable exhaust.

If it ain't broke, why fix it?
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