Bad gas milage?

[TBFK]

Ok, so i'm only getting 13.5 MPG!!!! I'v used Seafoam, changed the fuel filter, spark plugs, spark plug wires, and replaced a few things having to do with my EGR system. My Gas milage is only getting worse. When I bought the car on 1/28/11, it was getting 16-18 MPG, and now it's only getting 13.5.. I don't have a lead foot, I don't race, I don't get on it very much at all because i'm getting horrible gas milage, and I don't have that kind of money to spend. Is their anything else I can try?

[evolutionmovement]

O2 sensor, knock sensor, check if injectors are leaking.

[TBFK]

The injectors aren't leaking, and I haven't replaced either of those sensors yet. Would any DTC's be popping up if my knock sensor is bad?

[evolutionmovement]

I think it stores a code for the knock, but will only display it in check mode. Mine went and I never got a code (though, in my case, it seemed to just not work and the ECU had no clue). Does the car feel slow? When it detects knock, or what it's SUPPOSED to do when it fails, is go into limp mode, which retards timing and increases fueling. Of course, it may have been in limp mode since you bought it. The knock is a common failure and an easy fix, as well as the O2 (though that depends on how stuck that bastard is). Generally, the body of the knock sensor will be cracked when bad, but I don't necessarily think that not seeing a crack means it's definitely good.

[Legacy777]

Can you please clarify which car you're talking about. I'm assuming it's the 97 Legacy, but it would be good to confirm.

[evolutionmovement]

Uh, yeah, in that case you should probably be getting a code for the O2 if it's bad and maybe the knock sensor as well. Reading comprehension fail.

[TBFK]

Can you please clarify which car you're talking about. I'm assuming it's the 97 Legacy, but it would be good to confirm.

It's the 97 LSi.

I think it stores a code for the knock, but will only display it in check mode. Mine went and I never got a code (though, in my case, it seemed to just not work and the ECU had no clue). Does the car feel slow? When it detects knock, or what it's SUPPOSED to do when it fails, is go into limp mode, which retards timing and increases fueling. Of course, it may have been in limp mode since you bought it. The knock is a common failure and an easy fix, as well as the O2 (though that depends on how stuck that bastard is). Generally, the body of the knock sensor will be cracked when bad, but I don't necessarily think that not seeing a crack means it's definitely good.

I don't happen to know where the knock sensor is, and I haven't had any codes thrown recently. I doesn't feel to slow. It feels like it pulls pretty good for being stock. So if it is in limp mode then I can't imagine how well it does with a good knock sensor. The knock sensors look like they run about $130

[evolutionmovement]

I was thinking you have a 1st generation OBD1 car. I think yours has the later, improved knock sensor. Anyway, it's at the back of the block on the left side in front of the bell housing.

[TBFK]

I was thinking you have a 1st generation OBD1 car. I think yours has the later, improved knock sensor. Anyway, it's at the back of the block on the left side in front of the bell housing.

No, i'm sorry. I have the OBD2 edition. I also have a Diagnostics tool which lets me view the codes, and check the monitors.

[Legacy777]

You should be getting way better mileage than that. Have you checked to see that you're getting all cylinders firing. If you remove one spark plug wire at a time, I assume the engine will run rougher. Try all four and see if there's any differences between cylinders. You could also try removing the electrical connector for the fuel injector and perform the same test to see if the engine runs any differently.

[TBFK]

Alright Josh I did what you told me to do and unplugged everything one at a time, and the injectors and plugs are all working. I don't know what else it could be. What else do you think it could be?

[wtdash]

HI,
.02 here.....O2 sensors are common issue, once you get up there in mileage. Still my vote, even w/out codes. You do NOT have to buy from the dealer. If you're willing to do some wiring, the universal (for your car) will work.

Did you use the recommended NGK plugs (either $$$$ plats or coppers) and wires? Yours has the 2.5, correct? If not, someone did a swap and the 2.2 may not be hooked up properly.

Also, the CatCons could be bad/clogged/etc....not sure how to test, but if the catalyst breaks up inside they'd cause issues.

BTW, check out the USMB site...they deal a lot more w/the 2nd Gen stuff.

GL,
TD


"run ruffer" - Really Josh? Really?

[TBFK]

Hello O2!

I used BWD Platinum Wires, I have the EJ25. I've thought about buying new O2 Sensors, but I really don't have the money. A total of $120 for both O2 Sensors:( Are they the three wire or two wire Sensors?

I checked out that site, but I didn't find it very helpful.

Do you think that this MagnaFlow Universal Catalytic Converter will work? Part # 99194HM

[TurnNburn]

I notice when i use additives in my gas the milage drops a lot. Like 3-4 MPG. A friend of mine gave me like 30 bottles of SPT injector cleaner for free. I started using it and watched my power and fuel economy drop off. So ran it almost all the way dry and filled it back up without that stuff, then the car ran much better. And i stopped using it.

Fuel additives
http://www.youtube.com/watch?v=2jbcCr2ll3c

As for the cats, if you able to take off that part of your exhaust and shake it there shouldnt be any rattles or debris coming out. Thats the only test i know of that doesnt involve cutting holes in before and after your cat and using a 5 gas machine to mesure the difference. Iv seen some that sounded like rain sticks with all of the honey comb stuff broken off in there. But the one you have posted is not 50 state legal, which means that it doesnt work very well at converting emmissions and you wont be gaurenteed to pass smog. Thats why its cheap. You get what you pay for.

[TBFK]

My gas milage did go up to 14.6MOG after that tank of gas. As far as the Cat goes, I live in Oregon so we don't have any emissions. But i'll still check it out my Cat before I buy a new one. Thanks for the help guys!

[TurnNburn]

yeah im from bend, or. My car is registered up there still, thats how i can run no cats down here. I would say ditch the cat and straight pipe it, but i think that only works for turbo'ed cars. 14 is still pretty low, but im not getting much better @ 16. Although, on the freeway i get like 25mpg cruising @ 70mph.

[TBFK]

Bend huh? lol. What made you move south? If I ditched the cat and straight piped it, would that trigger my engine light or throw a DTC? I've thought about doing that before but I don't wanna mod my car if it's gonna cause it to throw codes or not work like it's supposed to. I plan on selling it some where in distant future for a down payment on another Subaru, hopefully.

[TurnNburn]

Im only down here to go to school at UTI (universal technical institute). Mostly for the diesel program as that is where the money is at, but im also taking the auto program too. Im actually taking 3 ASE's tomorrow. I graduate in a few months and will be moving back to bend shortly after.

Now back on topic. lol . Removing the cat will almost definitely throw a check engine light. P0420 is probably what will show up since that is the cat efficiency code. If your cats not there its not efficient. And thats what i was getting at in my last post, because even when you put on that new cat it might not be efficient enough to keep that code from popping up. Iv seen it happen, especially with some high flow cats.

But there are some ways around it. I used this on one of my impreza's. Im sure there are some threads on how to's on here for a write up. But basically put this on your rear O2 (I used both to work). The rear sensor isnt actually sensing the cat is working, but rather comparing the front to the rear. So by pulling the sensor out of the exhaust stream, a lot, the sensor thinks the cat is working and wont throw a code and will not affect the performance of your car besides excess emissions. This will not fix your gas milage though... It will probably make you get less because your car is going to sound so much more awesome your just bound to drive it harder
http://www.rockauto.com/catalog/raframe ... 002-513400