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Old 07-19-2015, 08:12 PM   #1
sup_uni
Scooby Newbie
 
Member#: 426112
Join Date: Jul 2015
Location: Oregon Lat 44
Vehicle:
2005 Saab 9-2x Aero
Arctic Silver

Default ej20 o2 sensor on an ej25

I purchased a 2005 Saab 9-2x aero yesterday and almost immediately after buying,probably 50 miles down the road i toss a CEL, P0031 so I know that I am having an issue with the upstream/front o2 sensor.

I get this sensor pulled today and it looks like the tip melted in the exhaust manifold. Strait white crust like the exhaust is/was running lean as hell.

After cleaning and putting the sensor back in and resetting the CEL the issue came back almost immediately. After running the part number (Denso 22641-AA042) it states that this is an o2 sensor for an ej20 motor, the car currently has an ej25 installed (I was told that it is an ej257 sti motor, but as of this point i haven't been able to confirm the exact 25 model).

My question is, would a 25 melt the 20 o2 sensor? From my understanding of the sensors they are the same but im not quite sure then why the denso part number would only show compatibility for a 2.0 motor. Also is there a way to know for sure where this motor came from (a ej255 or ej257 or what?)

Right now the car is sputtering HEAVY under a hard excel but if i barley give it fuel it seems to boost and run fine, just takes a lot longer to get to speed.

I didnt even think of taking a photo of the o2 damage while it was out however i snapped a pic of the part number and you can kind of see the color of the lean burn at the bottom of the sensor.
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Old 07-20-2015, 10:02 AM   #2
dstroy
Scooby Specialist
 
Member#: 283711
Join Date: May 2011
Chapter/Region: NESIC
Location: Newport
Vehicle:
2012 STI sedan
Black with scratches

Default

Quote:
Originally Posted by sup_uni View Post
I purchased a 2005 Saab 9-2x aero yesterday and almost immediately after buying,probably 50 miles down the road i toss a CEL, P0031 so I know that I am having an issue with the upstream/front o2 sensor.

I get this sensor pulled today and it looks like the tip melted in the exhaust manifold. Strait white crust like the exhaust is/was running lean as hell.

After cleaning and putting the sensor back in and resetting the CEL the issue came back almost immediately. After running the part number (Denso 22641-AA042) it states that this is an o2 sensor for an ej20 motor, the car currently has an ej25 installed (I was told that it is an ej257 sti motor, but as of this point i haven't been able to confirm the exact 25 model).

My question is, would a 25 melt the 20 o2 sensor? From my understanding of the sensors they are the same but im not quite sure then why the denso part number would only show compatibility for a 2.0 motor. Also is there a way to know for sure where this motor came from (a ej255 or ej257 or what?)

Right now the car is sputtering HEAVY under a hard excel but if i barley give it fuel it seems to boost and run fine, just takes a lot longer to get to speed.

I didnt even think of taking a photo of the o2 damage while it was out however i snapped a pic of the part number and you can kind of see the color of the lean burn at the bottom of the sensor.
No, both sensors are designed for turbocharged engines. That extra half liter of displacement doesn't make the 255-257 run hotter than that thing can handle. The sensors come out white all the time. Whoever had it before you probably dropped the motor in without taking that sensor out of the manifold before they put it in, they break super easy...like even dropping it onto the shop floor from waist level and they break.

http://forums.nasioc.com/forums/show....php?t=1667168

Scope it and find out what pistons are in there, and the heads are stamped with the casting numbers. Then you'll know if you have a legit 255 or a 257 or a frankenmotor.
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