# bogging down



## hunsberger1 (Mar 3, 2014)

the more I have been reading thru previous post a lot of people are talking about a cat coverter being plugged does anyone know if I do an exhaust backpressure test what it should read on an 01 Altima thanks


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## rogoman (Dec 16, 2004)

If you use a vacuum gauge connected to a front O2 sensor port, the reading should be no more then 1.0 psi.


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## smj999smj (Jan 1, 2006)

You don't use a vacuum gauge at the O2 sensor port to measure back pressure; you use a low pressure gauge, one capable of reading 0-15 psi, generally looking for a reading of less than 1.5psi. I have an exhaust back pressure tester which makes it fairly easy. It comes with a hose that screws into the O2 sensor bung and the gauge shows green, yellow and red zones, along with psi readings, to show the back pressure readings when testing. You can usually pick these up for around $40-60. Here's a good article on testing:

Exhaust Backpressure


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## rogoman (Dec 16, 2004)

rogoman said:


> If you use a vacuum gauge connected to a front O2 sensor port, the reading should be no more then 1.0 psi.





smj999smj said:


> You don't use a vacuum gauge at the O2 sensor port to measure back pressure; you use a low pressure gauge, one capable of reading 0-15 psi, generally looking for a reading of less than 1.5psi. I have an exhaust back pressure tester which makes it fairly easy. It comes with a hose that screws into the O2 sensor bung and the gauge shows green, yellow and red zones, along with psi readings, to show the back pressure readings when testing. You can usually pick these up for around $40-60. Here's a good article on testing:
> 
> Exhaust Backpressure


The only reason I said that you can use a vacuum gauge is that many good vacuum gauges have a double pointer and a second psi scale from 1 - 7 psi.


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## smj999smj (Jan 1, 2006)

That would make it a vacuum/pressure gauge, wouldn't it? 
You can use the vacuum gauge on a ported vacuum source on the intake to test for a clogged exhaust, however. Or there's always the "old school" way of removing the converter and driving around with open exhaust...but neighbors and police officers aren't particularly fond of that method!


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