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2004 Subaru Outback Sedan H6
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Discussion Starter · #1 ·
Hello to anyone reading. I decided to make a post after following the forum a bit for some time. It has been very helpful for a lot of things I have done to my vehicle so far. I recently purchased this car about three months ago. This is my first vehicle. I purchased it from a nice couple at a fair price with 120k miles. I have put another 700 on it so far. I always thought my mpgs were terrible but didn't really pay attention until a bit over a month ago. I consistently get 10 mpg, a little better if I drive mostly highway, 13 at best. Only other symptoms it has is the smell of gas in the cabin on cold starts for a few minutes, it used to make relatively rough shifts but after I had the transmission fluid and filter changed, it really only does it when shifting into reverse. Seems to accelerate fine. A little delay when I floor it, but it really zooms. Maybe there are other subtle symptoms that I do not notice. Feel free to inquire about it.

I did purchase a bluetooth diagnostic scanner a month ago. Between idle and driving, my wideband o2s in both banks tend to sit around 3.5-3.8 volts. Short term fuel trim on both banks goes as high as -30% to 20%. Long term stays within the -10% to 10% range. I have no sort of lights on the dash or engine codes on my reader.

I have done a few things to try to address it but with no avail. I did the usual motor oil change and oil/engine air filter change. I cleaned the throttle body, used an entire can of seafoam in the tank and also did some through the vacuum line under the beauty cover for the engine. Fixed leaking exhaust between the flanges before the muffler(not that it helps but wow the car doesn't sound nearly as loud now). Also had 4 brand new tires put on for snow. I also did a bunch of other things to fix issues they mentioned and it was all fairly easy but is totally unrelated to my driveability and mpg.

I do like to do things myself but know I should go to a mechanic. I like to do things myself and save money but do not mind the idea of spending the money to have a mechanic diagnose the problem for me. But beforehand, I wanted to see if there was anything I can try to fix it or do to diagnose the issue definitively. I like learning things and any input would be great. I did try to see if I can get at the fuel injectors but it does appear to be a little over my head and I can't find much material for how to get at them.

So what do any of you reading think? Bad O2 sensors? Bad or stuck injectors? Bad TPS? Bad fuel pressure regulator? Or something else. I do have 6 new iridium spark plugs I purchased a month back as well as a pcv valve but haven't put them on yet. Was going to pay a mechanic to put them on as I doubt they were ever changed since the transmission fluid was never serviced since the car came out of the factory. But I think it may be better to save the money for whatever may be wrong with the car. I love this car. Want to make sure it is taken care of and goes for a very long time. And do as much as I can myself and do it correctly. Any input from anyone for a car noob like myself would be great! Thank you to anyone for reading!
 

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miles on this. is it a cloth seat six, a Bean, or a top dog VDC?

I would think you got a weeping gas line, (big or small) under the hood. the hard ones to find are the fuel regulator pressure releif things on the big flexible rails down each side of the engine. (you have to find such things when it is really cold out and take a pic for a mechanic to find again later,...or you have to leave it over night in the cold and just add to the clock of them looking for it).

the lines going into the PCV on these get a little brittle to work with. be careful if you try.



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what brand plugs did you buy,...Subarus like Ngk only. this came with NGK double plat. when I asked NGK about the newer Iridium IX, they said the double plats would actually last longer in the US spec year 2001-2004 EZ30D.

http://www.rockauto.com/en/catalog/subaru,2004,outback,3.0l+h6,1426867,ignition,spark+plug,7212

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here is a thread about changing them as a DIY:
http://www.subaruoutback.org/forums...-how-change-your-h6-spark-plugs-easy-way.html

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but to get to 10mpg, you might have a few things going on. is this all short trips with lots of parked idling , or in traffic?
 

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2004 Subaru Outback Sedan H6
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Discussion Starter · #3 ·
Thank you for the reply! That was fast! Very informative! It is just a plain H6 outback sedan, leather seats, bought at 120k miles, 120.7k now.

I heard a leaking gasline could be a contributing factor. However where would I check that from? Top of the car, underneath, etc?

Also I did buy NGK and everything I bought or will buy is oem or will be the brand they built the car with like denso and such. Gotta treat the car right haha. I did also hear double platinums do perform better but didn't know they last longer, thought the iridiums did, interesting to know.

I put 7 gallons of gas in the car. Drive it until the gas light comes on and fill up immediately after. I average about 70 miles every time I do that but have hit 90 when I drove 60 miles highway. I do drive about a half mile to work daily. Lots of other small local driving too. Cold winter and lots of snow so I didn't want to use my bike. Commutes of about 5 miles probably twice a week. Stop and start traffic. I also try to drive atleast 20 miles highway every fill up, give it a bit of gas, keep things clean and let the car stretch out a bit. Used to warm up car for about 5 minutes before going places however I did hear that idling does use a lot of gas so I really only warm it up for a minute or two now after not running for a few hours, especially if it is cold.

I do also think that there can be more than one factor making my mpg so bad and it is a bit concerning. I hope it is a leak and bad o2 sensors, easy fairly cheap things. Not bad injectors or something else that would be a bit more challenging.
 

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lots of limited H6 sedans poking around.

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fuel leaks are usually around the top of the engine, but there are lots of places to look and it dissipates so fast.

so when you smell it and its daylight, get out and look with a flashlight .

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the short trips, and parked idling are really killing you, typically people with these report like 16mpg on a 10 mile urban compute when its cold.

6 cylinder gets thirsty in parked idling, the only reason I do it anymore is when I am physically cold in the car and need the heat. (and I wear really warm cloths so I can shut down for a little while).

be glad you don't have a turbo 2.5 (those get even worse mpg)

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lots of things can make for bad mpg: a front o2 sensor will make a lot of codes and misfires too.
(rear ones do nothing but post a horseshit po420 code).


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this car takes high octane, if you put low grade stuff in, you get poor mpg and bad shifts. (it really hates going down in octane,...takes about half a tank for the ecu to "digest" what you put in there and adjust fuel trims, and transmission shift points). mine has run on a steady diet of 93, since new I put 91 in it a couple times to see how it would go. but went back to 93..

I would fill it. and not let it go below a third. sometimes leaving all that big void in a car makes for condensation in the tank., seafoam is a great gas stabilizer and also cleans up condensation and resins though.

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as time goes by you or a mechanic might find something else wrong, like a sticky brake or a wheel bearing. those things hanging up really waste gas in cars. (you have to put more force on the gas pedal to over come such impediments).

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if you got a windows laptop you can get Rom-raider, and a $10 Vag cable and start logging and posting up. here is a current thread about using that to get after a EZ30D with a TPS code:
http://www.subaruoutback.org/forums...e/462009-2004-h6-ez30-stalled-stop-light.html
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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do you use high octane fuel? you should

consider 1 or 2 more drain and fill cycles on the trans - check its fluid level while idling after moving the lever thru each gear. top-off slowly, a few ounces and check level frequently while sneaking up on full levle.

front diff's stick is on the other side, lower and further back, it and the rear diff could probably use new gear oil.

CEL on? what code(s) ?

get the plugs changed, look for oil on the coil boots and if any is found, do the valve cover gaskets at the same time as plugs. (I wish I had)

are the tires the correct size? if not, they could throw calculations off. I get that people want the car to be comfy in extreme heat or cold, but more than 10-15 seconds idling is a waste.

both my soobs had fuel smell in winter , still tracking-down some on the H6, get a Philips and maybe an offset philips and tighten every fuel hose.

engine temp sensor and knock sensor can possibly be bad/out-of-range and not throw a code.
 

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Discussion Starter · #6 ·
The older outback wagons are very common around here. H6 seems to be a bit of a rarity though. Took me a while to find this one for sale, no others for months.

Oh I didn't mention but I have put 93 octane in the vehicle since I bought it, says on the gas cap. Considering the car had 14 year old transmission fluid in it, they PROBABLY didn't run premium either. Heard that can really gunk things up which makes me think maybe I have injectors stuck open. But i'm sure any major issues i'm theorizing would be throwing codes or lights or showing more obvious issues with driveability. But there is the possibility that it just isn't doing those things. I did have a code after seafoaming through the vacuum line though, which was to be expected. That all went away though.

I did try to occasionally look for wet spots under my car or under the hood, but I never REALLY looked, definitely have to give it more attention and check on cold starts when I smell it. Hope it turns something up.

I did make a few calls to shops, they all seem to universally say it is my O2 sensors, maybe it is. I am half tempted to spend $200 for the pair and throw them on but I probably shouldn't.

May be worth noting but when I got my transmission serviced they said the area for the oil filter had quite a bit of oil leaking around it. However after I changed out the oil and got an oem filter on (the people I bought it from had some fram on it) I have not seen any leak like they shown me since.

I do know poor mpg is expected for the winter, stop and start short trips and such. But 10 mpg is throwing a red flag to me. Hoping it does end up being something simple, new findings here and there that end up making a difference.
 

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Discussion Starter · #8 ·
do you use high octane fuel? you should

consider 1 or 2 more drain and fill cycles on the trans - check its fluid level while idling after moving the lever thru each gear. top-off slowly, a few ounces and check level frequently while sneaking up on full levle.

front diff's stick is on the other side, lower and further back, it and the rear diff could probably use new gear oil.

CEL on? what code(s) ?

get the plugs changed, look for oil on the coil boots and if any is found, do the valve cover gaskets at the same time as plugs. (I wish I had)

are the tires the correct size? if not, they could throw calculations off. I get that people want the car to be comfy in extreme heat or cold, but more than 10-15 seconds idling is a waste.

both my soobs had fuel smell in winter , still tracking-down some on the H6, get a Philips and maybe an offset philips and tighten every fuel hose.

engine temp sensor and knock sensor can possibly be bad/out-of-range and not throw a code.
Yes on the high octane. Ever since I bought it.

And I also did not mention but I do intend on getting my differential serviced. Fluid is most definitely what was in it from the day it came of the assembly line.

No CEL or codes of any sort. Maybe there are for smaller non engine related things but my obd scanner doesn't do any more than CEL codes for Subaru.

Tires are the correct size, do currently have winter tires on, tires on it when I bought it would have probably failed an inspection haha. No change in MPG from changing them though. And also why do the valve cover gaskets? How often do they recommend swapping them out?

Wouldn't the symptoms of knock or a temp issue be obvious? Or would they be similar to what I am experiencing?
 

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valve covers / plug orings
only if they are leaking oil externally. (the one on these that likes to leak is the drivers side rear valve cover on a US spec one).

mine use to spot the floor, I bought the gaskets, but did not put them on yet as it stopped dripping.

agree with a few more drain and fills on the ATF, and diff lube swaps.

take some pics of the plugs when they come out. post them up. I want to see what 120,000 mile double plats look like.

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and look on the bright side: 1 more month of winter. (at least on the calendar).
 

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Discussion Starter · #11 ·
I'd like to thank everyone that replied so far. I am very surprised I recieved so much input so quickly. Lurking these forums I knew everyone was knowledgeable and helpful but I didn't expect this much help! Thanks again!

I should have mentioned that I had a total flush of my transmission. Heard it can make a bad transmission worse but I opted for a flush to get all that bad fluid out and convenience. They use good synthetic fluid at the shop I went to and used the correct filter for my car. Would it still be necessary to change fluid out again?

I will definitely do the diff. Cheap to do and definitely necessary with how bad that transmission fluid was.

I am very curious how the plugs held up as well. Will post pics of them when I have them changed. I am confident the iridiums will do just fine. Would be nice if doing the plugs fixed my issues though. If I do not have any gas lines leaking at all or any brakes sticking would it be recommended to have the plugs and diff fluid changed out before anything else? Or would there be something else I should do first?
 

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if the temp sensor incorrectly sends the ECU a signal representing the engine is still cold after warm-up, the ECU maintains xtra fuel thru the injectors like a 'choke' setting.

If the trans was neglected, the new fluid is quite possibly cleaning some gummy deposits from valve bodies, maybe one more drain/fill (which only gets about 40% of the fluid out) could still be helpful - hard to say. many people also report success with 'delayed engagement' problems getting better with addition of a bottle of Trans-X on the final fill. I might be tempted to wait for results of one more drain/fill and then see how it behaves.
 

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if the temp sensor incorrectly sends the ECU a signal representing the engine is still cold after warm-up, the ECU maintains xtra fuel thru the injectors like a 'choke' setting.

If the trans was neglected, the new fluid is quite possibly cleaning some gummy deposits from valve bodies, maybe one more drain/fill (which only gets about 40% of the fluid out) could still be helpful - hard to say. many people also report success with 'delayed engagement' problems getting better with addition of a bottle of Trans-X on the final fill. I might be tempted to wait for results of one more drain/fill and then see how it behaves.
that is a great point:

the EZ30D at cold start up races the engine. at like 1300rpm? while in park, ....this is the ECU trying to heat the cats up fast. and when the cats are cold and you stand by the back of the car at this time it does stink like a 1970 chevelle in a parade.:frown2:

but when the engine is warm on the coolant temp gauge: the idle speed in park should be like 700rpm.?
(if left parked running for a typical winter warm up, that should kick down on its own without a throttle input like a old fashioned car)

so I wonder what the OP's is doing now.


@Glennda5id @idosubaru etc. any advice on the transmission of a US spec 120,000 mile 2004 H6 limited sedan, that has had its first drain and fill ever?


and @KM3695 there are more ez30D and EZ30R people on this board then anywhere else in the know universe.

if you click this link, scroll down to the about my car section you can type out "04 H6 limited sedan". and maybe something for a location, as a 2004 in places outside the US / Canada is the newer body.

http://www.subaruoutback.org/forums/110-gen-2-2000-2004/...do=editprofile
 

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1. Check for dragging brakes - I wouldn't expect that low of mileage but maybe if combined with that awful abuse of a commute it has.....
A. Slides need greased with SilGlyde or other high quality grease. That permatex and other brake grease suck and some shops still use it.
B. Throw away or replace the slide pin bushings. They routinely swell and are problematic and pointless.
C. Check the brake pad retaining clips - they can be bent or have a ridge of solidified built up debris. I replace them once at some point in the life of a vehicle as a matter of maintenance.
D. Take note if any pads are unevenly warn (a given pair at one wheel, and both pairs compared to each side of the vehicle).

Your Subaru brakes, calipers, and rotors will last the life of the vehicle if you follow those directions above and change the fluid. Replacing components blindly is poor quality maintenance.

2. I wouldn't change the transmission fluid again, they already flushed it and you had preexisting conditions. Next.

3. Check the oil level and smell the dipstick or dipstick port - does it smell like gas? Is the oil high?
Take note of the oil level and check it over time and see if the oil level is "rising" - which might not be a good indicator anything on an older engine with oil leaks/consumption likely anyway.
You've already indicated gas smell so it's likely coming from the exhaust or oil.

4. Drain the oil and look/smell for gas in the oil.

5. Maybe you can inspect the injectors or plugs for signs of leaking and identify which one is bad, if it is.

6. You can swap in used injectors (they rarely fail) or RC Engineering and witchhunter are companies that rebuild them and pre and post flow test them.
Car-Part.com--Used Auto Parts Market

7. If cost is an issue you can buy 2 used injectors and swap them with two cylinders and see if it changes. If not, switch two more out and wash rinse repeat until your issues improve.

10mpg is terrible and if it's related to a leaky injector you want to remedy that immediately as gas dilutes the oil and is bad mojo.

be nice if you could do a proper check: Fill tank to FULL, drive, fill tank to FULL again and properly calculate mileage. And do this on a highway trip where mileage is consistent and gives a good base line.
 

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i wouldn't worry about the transmission fluid, unless there's some symptom you didn't tell us yet that started after the flush -
certainly not now or as a root cause of your current issue.

people routinely drive 150,000 miles without changing ATF or have high mileage transmissions flushes. the majority doesn't give a rats left testicle about car maintenance, have a 'if it aint broke dont' fix it mentality beyond oil changes and 'tune ups', and think of car forums about as much as collecting beetle larvae. i am not at all recommending that and think it's a poor idea, unwise, and pointless not to change fluid, i'm just saying that when you look at what's happening in the real world there's not much to worry about...and actually if one pays attention it's a very informative dataset and service they provide by ignoring maintenance. hahaa
 

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Fuel trims seems a bit out of whack. I would start with the spark plugs.

Can you get the car fully warmed up and report the fuel trim when driving at constant speed between 40 and 50 mph, on both banks and fuel trim at idle on both banks.
 

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Discussion Starter · #18 ·
@1 Lucky Texan
Exactly how could I diagnose a problem with the temp sensor? Any way to do it on my own? I did buy a bottle of transx. I assume I put in a quart and take out a quart of transmission fluid first? Will put it in when it isn't down pouring, hopefully tomorrow when I am off. Is another drain and fill necessary even though I had a complete flush?

@eagleeye
My car does surge to about 1300 rpm on cold starts and does smell in the cabin when doing that but it does dissipate after it goes back down to about 6-700 rpm. Used to fluctuate a bit in idle by 1-200 rpm bur after cleaning the throttle body recently it does seem to be more steady and make less noise. Should I be smelling this in the cabin on start up even without using any climate control?

@idosubaru
I will definitely give the brakes a look over soon, probably when I change the pads and such. When I got my new tires put on like 500 miles ago they said I have about 3000 miles left on the pads. Thankfully my neighbor has been a mechanic for a long time. Whenever I am working outside he'll always see what I am up to. If I can't catch an issue with anything i'm sure he will. I'll be sure to give it all a good cleaning and replace whatever else needs to be replaced when I do.

As for the oil, the oil in the car was terrible when I replaced it. Smelled and looked terrible, probably in there too long. Haven't had an issue since replacing it though. No odd smells or colors, level is consistent. What would gas in the oil look like? I really do want to look at the injectors. And get them cleanee regardless. I know off car cleaning is superior to on car cleaning however is getting the injectors cleaned on car actually helpful? I did fill the tank up today as well, i'll try to do more highway miles for a more accurate reading.

@Glennda5id
I did some highway driving today and did check out the numbers. Vehicle did warm up plenty beforehand. They are fluctuated in these ranges.
50 mph
STFT Bank 1 : -17.2 to 3.9
Bank 2 : -19.5 to 5.5
LTFT Bank 1 : -0.8 to 6.3
Bank 2 : -3.9 to 3.9

Idle
STFT Bank 1 : 0-4.7 mostly 3.1
Bank 2:-6.3 to 4.7 mostly 3.1
LTFT Bank 1 : -0.8
Bank 2 : -3.1

Numbers were a bit more wild before the throttle body cleaning. MPGs are still just as bad though.

It is crazy how many of you replied with all of these recommendations. From what I gathered so far I am going to do the easy stuff and stuff I planned on doing anyway first. Going to put transX in tomorrow, get my differentials serviced tuesday(would do it myself but no stands to keep car totally level and labor is cheap here). Soon I want to also get the spark plugs switched out. I need to do the brakes soon and will also make sure I check for any issues there. I do want to see if I can get the injectors clean but the turn around times are like a week and I do not have a second vehicle. But the cost is so low and it seems necessary. Should I definitely go that route soon as well? I am also going to give a good look for weeping lines or any leaks in general. Thank you again for all the replies, this is such a helpful forum! Sorry about all the questions, but I just want to learn as much as possible.
 

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you should not be smelling fresh gas at all.

only when you stand at the back of the car when the engine is racing cold should you smell hydrocarbons from a too rich exhaust. (hot cats take care of that).
 

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Based on your fuel trims you are rich at load and doing not too bad at idle. Since these engines are speed density, that would indicate to me incomplete ignition in the cylinder under load. Most likely worn plugs or possibly an issue with the valves. My experience says plugs are the issue though.

If you can, do a compression check with the spark plugs out (pain on these cars with engine in car), but I would probably just skip to replacing spark plugs.

If you had a leaky injector fuel trims, would be really off at idle. I see small amount of excess fuel at idle and lots of excess fuel at load. Higher the load, harder it is for a spark plug to fire and worn plugs will be very weak in these conditions.

OE plug and the only plug I would use on this car is NGK 7654 #PLFR6A11 Laser Platinum. Subaru recommends 60k interval but they will go to 100k because they are a double platinum plug.
 
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