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Old 02-07-2008, 01:41 PM   #1
chip4761
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Default Horrible Mileage

Ok, here's the story...

I had a CEL about 3 or months ago, but never got it checked. The reason? I looked under the hood and a vacuum line or two were d/c'ed. Bad news there. Anyway, I reset, and no CEL since then.

The weird thing is the way my car has been running in general. When I accelerate, the rpms stay up around 1.5K even after I put the clutch in. It's like a super high idle speed. This problem is persists even after the car starts to warm up, and really only ceases after the car has been on the highway for awhile.

I've been averaging 16-18 mpg. Not cool. This could be any number of things, but I'm thinking maybe an O2 sensor, or something like that. Any ideas?
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Old 02-07-2008, 02:10 PM   #2
Subydude81
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Have you ever changed out the fuel filter? Dirty air filter? I don't think its a 02 sensor since your not throwing any codes. I know that is not a definite guarantee but since its not throwing a code I doubt its an 02 sensor.

Check that tire pressure. Its a 95' so it might be worth it to throw in a bottle of fuel injector cleaner. I am not one for these but I've always had new cars so I cant state if they work or not.
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Old 02-07-2008, 07:02 PM   #3
ToastermonkeyPat
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Hmm, I've been averaging about the same mileage and my car does the high idle thing just for a couple seconds after I put in the clutch sometimes. I'm thinking it may just be due to a dirty air filter. I changed out my fuel filter a while ago and it made a little difference too. I'm cleaning my air filter tonight. I'll let you know the results. Also, I've heard the pcv valve can cause bad mileage.
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Old 02-07-2008, 07:09 PM   #4
Spore
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I've also been logging my fuel mileage for a few months now and I've been getting 15-19 MPG and no CEL. I'm not sure why is it happening. I've brought it for servicing and got my fuel and air filters replaced. But the mileage is still not going up. I thought it was bad gas so I tried another brand and octane (from 87 to 89), and my mileage plummeted down to 10! I'm still trying to find out why is it happening...
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Old 02-07-2008, 07:32 PM   #5
naimouasta
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check the brakes? my dads 98 forester had terrible gas mileage, 16-18mpg. turns out it was the pistons in the brake caliper sticking. replaced and gas mileage returned to 22-23mpg average. messed up thing is the other calipers started sticking also within 4-5months. they are all replaced now and all is well; it just hit 161k miles. also when i replaced the first caliper i did fuel filter, air filter, pcv, and new spark plugs. definitely made a difference, engine became more responsive and idle was perfect.
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Old 02-07-2008, 07:46 PM   #6
JustinJS
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Quote:
Originally Posted by naimouasta View Post
check the brakes? my dads 98 forester had terrible gas mileage, 16-18mpg. turns out it was the pistons in the brake caliper sticking. replaced and gas mileage returned to 22-23mpg average. messed up thing is the other calipers started sticking also within 4-5months. they are all replaced now and all is well; it just hit 161k miles. also when i replaced the first caliper i did fuel filter, air filter, pcv, and new spark plugs. definitely made a difference, engine became more responsive and idle was perfect.
yeah that same thing happened to my 96. i had to replace 2 so far.
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Old 02-07-2008, 07:50 PM   #7
naimouasta
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yea its pretty easy to spot, if after driving, one wheel is noticeably hotter than the others, a stuck caliper is usually the case.
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Old 02-07-2008, 09:01 PM   #8
ITB H4
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Don't you guys hear any funny sound or perform different if a caliper got stuck??
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Old 02-07-2008, 09:33 PM   #9
RaceFaceXC
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Quote:
Originally Posted by chip4761 View Post
Ok, here's the story...

I had a CEL about 3 or months ago, but never got it checked. The reason? I looked under the hood and a vacuum line or two were d/c'ed. Bad news there. Anyway, I reset, and no CEL since then.

The weird thing is the way my car has been running in general. When I accelerate, the rpms stay up around 1.5K even after I put the clutch in. It's like a super high idle speed. This problem is persists even after the car starts to warm up, and really only ceases after the car has been on the highway for awhile.

I've been averaging 16-18 mpg. Not cool. This could be any number of things, but I'm thinking maybe an O2 sensor, or something like that. Any ideas?
When you discovered the vac lines off was it obvious where they were supposed to be connected? maybe they are not just vac lines but sense lines for something and they were swapped? just an idea.
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Old 03-28-2008, 10:54 PM   #10
chip4761
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Sorry to ressurrect, but still no dice. I think I'm going to check the pcv or whatever that little bugger is. Can't you test it by sticking your finger over the hole when it's idling?

A new and fun trick the car has been doing lately is jumping to a high idle on start. So fast and high that the starter gets stuck on the flywheel and I have to sometimes turn the car off and start it again hopes that I don't break teeth of the FW.
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Old 03-29-2008, 02:25 AM   #11
stormsubaru
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to check the pcv valve just pull it out and shake it. if it shakes back and forth it's still ok. if it stays in place then it's stuck and needs to be replaced. does your temp gauge read in the middle because sometimes high idle can be a faulty coolant temp reading (the car thinks it's really cold) and double check to make sure all your vacuum lines are in the right places, not mixed up. or maybe your throttle is sticking take the intake off and make sure the butterfly is returning all the way, if not spray some carb cleaner in there and even wipe it out with some lint free shop towels. there are a lot of things it could be but hopefully that will help...
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Old 03-29-2008, 11:25 PM   #12
00LGTP
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i am getting around 16, i have changed fuel filter, rear o2 sensor (it was bad anyway), pcv , spark plugs 10k ago, the only thing else i can thing of is the front 02 sensor. would that make a difference? my valve cover gasket it starting to get bad also, would the oil going onto the spark plug boot/plug make a difference also?
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Old 03-30-2008, 12:16 AM   #13
cmiovino
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I removed my spare tired and gained a whopping 3-4 MPG from 18-19 to 22! Now, that was my first fill up, we'll see how the others go. I look to be getting the same though... it's odd. I wouldn't image it would make that much of a difference... I was thinking 1 MPG at the most.
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Old 03-30-2008, 01:07 AM   #14
Chi_San
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Fuel filter. I changed mine and it made a huge difference.

O2, no. You would be getting 10-12 mpg with a bad O2.
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Old 03-30-2008, 02:33 AM   #15
imprezkid
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Im not sure if this helps, but now and then i take my throttle body off and apart and clean it out with some carb cleaner, can't hurt, im yet to even find the pcv on my 02rs, but have changed a fuel pump, could be a problem.

Bad cat? My car has one but doesnt through a CEL, dealer tested, but to low for them to get it on a lift. should i be sad or happy about that
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Old 03-30-2008, 12:48 PM   #16
00LGTP
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Quote:
Originally Posted by imprezkid View Post
Im not sure if this helps, but now and then i take my throttle body off and apart and clean it out with some carb cleaner, can't hurt, im yet to even find the pcv on my 02rs, but have changed a fuel pump, could be a problem.

Bad cat? My car has one but doesnt through a CEL, dealer tested, but to low for them to get it on a lift. should i be sad or happy about that

i am catless now, i have the O2 spacer in and the CEL is fine. anyway, my IM and TB as as clean as can be because i just P&P them about 2 months ago.
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Old 03-31-2008, 05:32 PM   #17
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I randomly got 170 miles on 3/4 of a tank the other day. My personal low. Usually its like 220
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