How to identify an engine, is it EJ251 or EJ253?

18324 Views 3 Replies 3 Participants Last post by Bill Stewart, Dec 11, 2013

Bill Stewart

Discussion Starter · Dec 10, 2013

The title says it all. I've got a 2005 Forester 2.5X that has had a blown engine replaced with a used one. How can I verify which engine they actually put in, EJ251 or EJ253 (should be EJ253)? I'm about to buy a new front oxygen sensor and the distinction is important.

The the new (used) engine was installed by my regular mechanic, not through a dealer, and they had a little trouble locating a used engine. The replacement runs great, but they couldn't get the computer to recognize it and had to send the car to a Subaru dealer to sort that out. The only troubling thing is that the speedometer runs about 4% fast and the gas mileage isn't quite as good. I had been getting 31 mpg on the highway, more that what it was rated, so I was quite disappointed that it fell to 28mpg.

Thanks for any help.

Bill

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dave5358

· #2 · Dec 10, 2013

Bill Stewart said:
The title says it all. I've got a 2005 Forester 2.5X that has had a blown engine replaced with a used one. How can I verify which engine they actually put in, EJ251 or EJ253 (should be EJ253)? I'm about to buy a new front oxygen sensor and the distinction is important.

The the new (used) engine was installed by my regular mechanic, not through a dealer, and they had a little trouble locating a used engine. The replacement runs great, but they couldn't get the computer to recognize it and had to send the car to a Subaru dealer to sort that out. The only troubling thing is that the speedometer runs about 4% fast and the gas mileage isn't quite as good. I had been getting 31 mpg on the highway, more that what it was rated, so I was quite disappointed that it fell to 28mpg.

Bill: This engine information was on a plate inside the engine compartment of the donor vehicle. I'm not sure where else it's located. How did you decide the new engine might be an EJ251? Or, an EJ253, for that matter? FWIW, my 2006 has an EJ255.

As for the speedo issue, why would changing the engine affect this? Did they swap transmissions as well? The only reason I asked this is because Subaru changed the final drive ratio in 2006 - made the car a bit more long-legged.

Is it possible that the dealer flashed the wrong firmware or something?

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GEORGEROV

· #3 · Dec 10, 2013

Hi Bill , To help identify the engine :

EJ 251 uses a map sensor to help with the air/fuel setting , whereas the EJ253 uses a Mass Airflow Sensor . If it has a maf then you will find this on the air induction tubing . If a map sensor then this will be located close by /on the inlet manifold .

On the speedo side then manufacturers build in a 5% error in the reading .

28miles per US gallon for an auto sounds good to me .

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Bill Stewart

Discussion Starter · #4 · Dec 11, 2013

@dave5358
My engine is not turbo-charged, so I assumed it was not the EJ255, which is DOHC. I got my inof from the Subaru EJ Engine wiki page.

I don't see any connection with the speedometer either. I'd just thought I'd toss that out to see what others thought. It's possible that it was always fast.

@GEORGEROV
Yeah 28mpg is fine. I never understood how the car was getting 31mpg, but for three years, that's what I got. It was a former rental when I got it. I'd sure like to know if there was anything they did to goose the milage. :icon_wink:

Bill

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