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exhaust leak before O2 sensor cause engine to run rich?


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#1 OFFLINE   ahardb0dy

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Posted 19 December 2012 - 06:35 PM

I always thought I had a leak in the exhaust some where, I thought it was under the truck. Monday after having the tires rotated and balanced I took the truck to a exhaust shop for a free inspection, the guy said it was leaking from the drivers side exhaust manifld but he couldn't tell if it was the gasket or the manifold was cracked, I said it was probably a broken stud as we all know that is a common failure.

Anyway I was thinking since the O2 sensor is after the exhaust leak could the leak be sucking air in causing the O2 sensor to think the engine is running lean and than tell the ECU to make it run richer?

94 pathfinder by the way


Thanks

#2 OFFLINE   Alkorahil

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Posted 19 December 2012 - 07:59 PM

In short, yes it can do that.
Is it enough to worry about? On a WD21 probaby not, the leak would have to be REAL bad as the sensor is so far back.

#3 OFFLINE   ahardb0dy

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Posted 19 December 2012 - 08:43 PM

Not worried really, the truck always seems like it runs rich, haven't checked using the ECU yet, but mileage seems lower than it should be, even though MPG is low to begin with. Think I got better mileage with my 4.7 V8 Dakota I used to have.

#4 OFFLINE   Tungsten

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Posted 20 December 2012 - 06:35 PM

Yes, it will most definitely run improperly if there is a leak before the oxygen sensor. You are better off unplugging the sensor and running the default mapping. I suppose you have the stock exhaust right?



#5 ONLINE   Precise1

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Posted 20 December 2012 - 08:06 PM

In short, yes it can do that.
Is it enough to worry about? On a WD21 probaby not, the leak would have to be REAL bad as the sensor is so far back.

I don't get this. A leak is a leak and will dilute the gasses regardless of the distance to the sensor, no?

 

B



#6 OFFLINE   ahardb0dy

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Posted 22 December 2012 - 08:15 AM

Yes exhaust is stock



#7 OFFLINE   Tungsten

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Posted 29 December 2012 - 12:28 AM

Unplug the sensor then so that it does not pick up the leak. It's not the best solution but should be good until you fix the source of the leak.






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