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Right now, my 1991 Subaru Legacy L Wagon is just getting worse and worse mileage as time goes on. I want to assume it's because of the o2 sensor. It's approximately 18 to 20 in the best averages when I drive it like grandma. Other than that, the fuel gauge does not last long and I use 10 gallons before I know it. It used to get anywhere from 23 to 24.

 

I'm in the money struggle enough as it is and this is just making things horrendously worse. I need some help asap if possible.

Edited by Ubatz

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Always best to go back to basics. How long has it been since a tune up of new spark plugs and plug wires?? New plugs and wires can help gas millage. An O2 sensor may help as well. If you are handy with a wrench, it is not much work to do this work yourself, and save what a shop would charge you.

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Always best to go back to basics. How long has it been since a tune up of new spark plugs and plug wires?? New plugs and wires can help gas millage. An O2 sensor may help as well. If you are handy with a wrench, it is not much work to do this work yourself, and save what a shop would charge you.

I did a tune up but not the plug wires and I haven't checked the coils either honestly. Plugs don't even have 10,000 miles on em yet. Might need to check the air filter again too.

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You're not leaking fuel right? From say, the filler neck?

Nope. It's all clean around there. Replaced stuff and haven't seen any wet spots even under pressure. I'm beginning to think it's running rich because it's been smelling like it lately so I need to check for an exhaust leak before the o2 sensor.

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I suppose I could mention I haven't done the plug wires or coils yet though. Haven't really thought about that

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Is it dripping black carbon water from exhaust or is it hard starting?

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Is it dripping black carbon water from exhaust or is it hard starting?

It does have that black carbon water yeah!

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However it starts super easy. It doesn't even have to do more than do a half a crank and it starts when its warm

Edited by Ubatz

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Maybe the knock sensor is bad?? I can't remember if a 91 has a knock sensor, but probably so.

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Maybe the knock sensor is bad?? I can't remember if a 91 has a knock sensor, but probably so.

I'm not sure where that comes into play. I will check to see if there's parts for it. Where is it usually located?

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The engine doesn't feel sluggish and it runs pretty good other than an erratic idle sometimes but I think that's just because it needs to be cleaned a little bit and it's very rare that it idles weird. I looked into it and it doesn't seem like it would be a problem considering the symptoms. When I first started my car if the engine was warm and it was really cold out and occasionally it would like flash on her stay on for a few seconds but nothing more than that. I might go into my ECU press the button and get the morse code flashes to see what might be up.

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Not to mention it starts right up when I try to.

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Our daughter just went thru a LOW GAS MILEAGE time on her 2001 Outback...... Was 26-27 mpg, down to 18-19.

 

Turned out to be DRIVER ERROR....... after driving this car for about a year, she started putting it into 3rd instead of Drive.

 

After trying to diagnose and changing parts, taking a ride with her was easily diagnosed from the passenger seat,

 

Not saying this is your problem..... but another reason gas mileage can suffer.

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I found that when I drive it a bit more to around 3000 rpms til it shifts it actually gets slightly better than normal. I grandmaed it and it lugged a lot. It doesn't like lugging. So that's helped a tiny bit

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Subaru engines are not built for low rpm high tourque. High rpm is no problem.

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Yeah, still need to figure out what else is the problem

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My ecu didn't give off any codes. Not even in the memory except for 3 short flashes but that didn't show up as an actual code

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