So I installed 2.5" cat back with a new muffler and I'm getting about 18mpg now, down from 22ish. Is this right? I had a similar setup on another impy and it didn't really change the mpgs.. Made it better actually. Ideas? I don't have a CEL or anything..

 

 

-Justin

I also noticed that when I install new air filters, I get awesome mileage for the first fillup like 24+ then it goes down again to 20-22ish. Now that its saying 18 it got me wondering.. Rear O2? Maybe

 

-Justin

This sounds like an ongoing problem, 22mpgs is low as is, maybe mass air flow sensor needs to be cleaned. I think the front o2 is what controlls air fuel mix and the rear one is just emissions related. Possibly leaky injector o-ring?

Did you reset the ECU? May need to "relearn" what normal A/F ratio is for your motor and because new exhaust=different flow rate could change the composition of your exhaust (i.e different A/F, egr recirc, ect)

I thought that the ecu on the 95 ej22s didn't retain that? That it cleared air/fuel at each shutdown?

 

I must be mistaken? Oh we'll, it's worth a try.

 

 

 

 

-Justin

My last 3 fill ups show the decline.. https://www.fuelly.com/driver/crazyman03/impreza?fu=4187199

 

-Justin

I live in a hilly area and my ej22 gets around 26 avg and both my mom and stepdads ej22 cars get between 25-28 of course that's not town driving either, but the worst milage I've ever seen out of an ej22 is 20mpg on my moms legacy with 250k and having to warm it up and go through a muddy driveway. I think there's something else going wrong, it sounds like the new cat made a differance, but even your best mpg seems low.

Front o2 deals with air fuel mix i dont think rear one affects the engine. I do know that changing the exaust can cause your engine to run differant, but I've never seen it decrease fuel milage.

Any exhaust leaks before the front O2 sensor? Manifold leaks at the heads or at the front cat flange can cause a lean reading from the front sensor. ECU sees lean voltage so gives more fuel to compensate.

no leaks that i can see/hear. The car at one point did have the manifold not attached to the heads; when i bought the car a year ago. Nothing now, that i can tell, and I've been crawling under there listening for leaks with the new exhaust. The only thing i can think of is the flange after the cat, the bolts broke off after i installed the new pipe. I fixed the gasket and installed new bolts.

 

I disconnected the battery for about 30 min on sunday. hopefully that'll help clear the A/F mixture settings?

 

It does feel a bit sluggish though. I wasnt able to pull the MAF off to clean it. Though, i didnt try too hard since i dont have any brake cleaner to clean it with. 

 

 

-Justin

Brake cleaner may damage the MAF element. Use MAF sensor cleaner or electronics cleaner.

 

Last time I had the manifold off of my car I could see tracks on the head where there are small leaks but I can't hear or feel them.

I have some new manifold gaskets to install now and thinking my mileage might come up by a few mpgs if I get rid of the leaks.

good to note.

 

as for leaks. I might just have to grab a new gasket for the cat-back flange. I did kinda have to make-shift it to quiet it down. I didn't think that a slight leak would make *that* much of a deal.

 

I'm thinking maybe MAF or O2, if i stomp on the gas, the fuel gauge drops. It drives kinda sluggish.. unless i just need a clean air filter and i'm just retarded??

 

 

-Justin

change the fuel filter? verify you are getting the correct PSI at the intake?

A leak AFTER the cat won't make a difference. The leaks that MAY affet mileage will have to be in front of the front cat. After the front O2 sensor it makes no difference.

A leak AFTER the cat won't make a difference. The leaks that MAY affet mileage will have to be in front of the front cat. After the front O2 sensor it makes no difference.

thats what i thought. I'm pretty sure its solid cat-front. I might have to poke my head back under there... when its not snowing that is :-/

 

 

-Justin

is this a larger diameter system? maybe it's worse at scavenging the CC due to lower velocity. Does it weigh more?

 

I have no experience with 2.2s , just a coupla thoughts.

Right side was leaking worse. Still couldn't actually feel a leak around the manifold though.

I think, that both (at least the D/S) manifold gaskets are new within the last year. maybe i should look at that too. maybe tighten up or get new bolts

 

 

-Justin

This pic was supposed to be part of the past post. Guess it didnt make it.

Well, i finally got around to getting gas. got 22.7 out of it. I cant say that was an accurate reading because i went up some mountain road and had a bit of highway. a video attached ;-) yea, i'm a dork..

 

 

https://www.facebook.com/video/embed?video_id=10152899622860727

 

Not to jinx it but usually this happens. I get great milage then it shoots down. i'll post at my next fillup.. probably wednesday or so.

 

 

-Justin

Edited April 27, 201312 yr by crazyman03