New legacy owner - Poor MPG and fluttering speedo

[wqbang]

Hey folks,

 

A new Subaru owner here. Love my legacy so far other than poor fuel mileage! I have read several threads here already addressing p[oor fuel mileage and I am trying to develop a plan of attack here to isolate the issue in my particular vehicle.

 

Details:

- 1996 Legacy Brighton AWD

- 2.2L

- 95K miles

- 4EAT tranny

- Tires are new and in grat condition all at 36psi.

- No evidence of torque bind, but plan on a complete ATF flush in the near future.

- Fuel is 87 octane with 10% ethanol as mandated by the State of Washington suring winter or something.... whatever.

- The speedometer needle flutters during acceleration below 20mpg. I not sure this is even related to the MPG issue and is a minor inconvenience.

- Recent plugs, wires, fuel filter and professional injector cleaning.

- Observed MPG is 18 city/ 24 hwy. EPA estimates for this car is 23 city /29 hwy

 

The suggestions I have heard so far is clean/replace the MAF, clean/replace forward O2 sensor, replace the engine temp sensor, replace PCV valve.

 

I may run by Schucks today and pull the OBDII data and can post it here.

 

I plan to attempt cleaning the MAF by spraying electrical contact cleaner and replacing the PCV valve first.

 

What are your recomended troubleshooting steps, and do you think the speedo issue could be releated in some way?

 

Thanks!

 

wqbang

Auburn, WA

[northguy]

Is this the 2.2 or the 2.5 engine? If you can determine it's not the fuel system, try doing a compression check. That may tell you something.

[wqbang]

Is this the 2.2 or the 2.5 engine? If you can determine it's not the fuel system, try doing a compression check. That may tell you something.

 

It is a 2.2L. I have updated my original post.

[nipper]

well the bouncy spedo affects the odometer. I do belevie thie is an electronic sped, so it can either be the spedo head, the board behind the head, or the speed sensor.

 

Winter fuel will reduce the mpg, and i think there is still alot of crap gas out there as per the EPA edict ... which if im correct should be ending soon.

If the car has over 100K on it do the o2 sensor as it probalably needs it anyway, and has the biggest influance on mpg over anything else.

Why did you get the injectors cleaned in the first place?

 

 

nipper

[wqbang]

well the bouncy spedo affects the odometer. I do belevie thie is an electronic sped, so it can either be the spedo head, the board behind the head, or the speed sensor.

 

Winter fuel will reduce the mpg, and i think there is still alot of crap gas out there as per the EPA edict ... which if im correct should be ending soon.

If the car has over 100K on it do the o2 sensor as it probalably needs it anyway, and has the biggest influance on mpg over anything else.

Why did you get the injectors cleaned in the first place?

 

 

nipper

 

Check engine light came on and had my mechanic look at it. Short term fuel trim was 10%. They recommended a tuneup and injector cleaning. Car runs great, but still gets poor fuel mileage. I normally try to do most of my own work (but I am just a mechanically inclined novice)... but time has been at a premium lately.

 

BTW, I have only owned the car for 3-4 weeks.

[wqbang]

I have cleaned the MAF with Electrical contact cleaner with no canges detected. I do notice that the exhaust when idling smells like fuel.... However, it had no trouble passing emissions. O2 sensor?

[TheBrian]

Are you sure your MPG is abnormal?

 

I have a '96 Brighton, 5MT. My worst tank of gas ever was about 21mpg. 0% highway driving, low temperature, snow, and winter gas. Yet the EPA figures sound about right for summer driving.

 

If your speedo is off, you're actually travelling more miles than the odometer records. Compare it against the highway mile markers on some long trip.

 

My car stinks of gas, too, at idle. The colder it is, the stronger the odor. I guess Subarus run richer than most cars during warm-up.

 

Definately do get your check engine light read before you start throwing sensors at it. Also, many sensors can be tested, which saves gobs of money vs. throwing parts at it.

[jcniest5]

If you want to improve gas mileage, use synthetic oil and do a motorvac. I gain 4MPG from using synthetic oil. I was getting 25 MPG when using regular oil, now I get around 29-30 MPG with synthetic oil. I haven't tried motorvac, but I heard it's great for improving gas mileage as well.

[SQ93]

When comparing against the highway mile markers, also use a stopwatch or watch and time the miles and see if the speed is being shown correctly. -CW

 

 

Are you sure your MPG is abnormal?

 

I have a '96 Brighton, 5MT. My worst tank of gas ever was about 21mpg. 0% highway driving, low temperature, snow, and winter gas. Yet the EPA figures sound about right for summer driving.

 

If your speedo is off, you're actually travelling more miles than the odometer records. Compare it against the highway mile markers on some long trip.

 

My car stinks of gas, too, at idle. The colder it is, the stronger the odor. I guess Subarus run richer than most cars during warm-up.

 

Definately do get your check engine light read before you start throwing sensors at it. Also, many sensors can be tested, which saves gobs of money vs. throwing parts at it.

[rweddy]

If you want to improve gas mileage, use synthetic oil and do a motorvac. I gain 4MPG from using synthetic oil. I was getting 25 MPG when using regular oil, now I get around 29-30 MPG with synthetic oil. I haven't tried motorvac, but I heard it's great for improving gas mileage as well.

I agree on the synthetic, I get better mpg since I switched.

[wqbang]

Are you sure your MPG is abnormal?

I have a '96 Brighton, 5MT. My worst tank of gas ever was about 21mpg. 0% highway driving, low temperature, snow, and winter gas. Yet the EPA figures sound about right for summer driving.

 

My BEST mpg city is 19, worst is 18. My best mpg highway is 24. This is significantly off from the EPA estimates by about 20%. This is calculated using the method of filling up and dividing by miles driven since last fillup.

 

If your speedo is off, you're actually travelling more miles than the odometer records. Compare it against the highway mile markers on some long trip.

 

I don't believe my speedo is off, it is simply fluttering occasionally below 20 mph. I will check my speedo using my GPS.

 

Definately do get your check engine light read before you start throwing sensors at it. Also, many sensors can be tested, which saves gobs of money vs. throwing parts at it.

 

Check engine light is not on currently.

 

I can try synthetic oil, but I am not sure that will make a big difference, only marginal. I am familiar with synthetics and understand that the lubricating quallties are significantly better but not enough to deliver a 20% improvement im fuel mileage.

 

Thanks everyone!

[Tiny Clark]

IMO, you won't see that much of an improvement with syn oil. My mpg seems to be about 25mpg average all the time, 2.2 with A/T, dino synth oil.

 

Your air cleaner is new, yes?

 

Maybe you could take a 100 mile trip or so and see how much gas you use to be certain of your MPG.

[wqbang]

IMO, you won't see that much of an improvement with syn oil. My mpg seems to be about 25mpg average all the time, 2.2 with A/T, dino synth oil.

 

Your air cleaner is new, yes?

 

Maybe you could take a 100 mile trip or so and see how much gas you use to be certain of your MPG.

 

Air cleaner is new.

 

I recently took a 600 mile round trip resulting in 24 mpg average.

[nipper]

600miles at what avg speed. How much stuff was in the trunk. 24 is a bit low, as i got between 24 (with spurts of triple digits) and 34 staying around 70mph. It could just be that when the car was new it wasnt broken in right when new.

What tires do you have on the car

 

 

nipper

[jcniest5]

Like I said earlier, synthetic oil + motorvac, that should give you close to the 20% you are hoping to get.

[TheBrian]

I just installed synthetic oil, and my fuel economy has plummeted. Because winter fuel and driving conditions have arrived.

 

No, you should be able to get close to the EPA figures on dino oil at any speed below 80mph. There's either something wrong with your speedo/odo, or something wrong with your fuel/air ratio, or both.

 

wqbang, I bought a used instrument cluster off a '95 L wagon last year, because I wanted its tachometer. Thus, I have a spare speedo, temp. gauge, and fuel gauge. I'd happily offload them for $(small)+shipping.

 

Brian

[wqbang]

TheBrian,

 

Thanks for the offer on the speedo. If I decide to replace it I will shoot you an email and take it off your hands.

 

To answer the other questions...

 

Tires are newish Bridgstones all inflated to 36 psi.

 

600 mile trip was at 75 MPH, including 2 trips over Snoqualmie pass. 4 passengers plus luggage. No winter driving conditions (cool, dry and 35 degrees).

 

My next steps will be:

 

1. Check my speedo using GPS.

2. Get a printout of the current OBDII at Schucks.

3. Replace O2 sensor

4. Complete ATF flush (needs anyway to prevent the dreaded torque bind).

 

The reason a motorvac is not on my list is because I just had the injectors professionally cleaned.

 

I will report back after these.

 

Thanks everyone!

[nipper]

Actually with that weight load, thats not a bad mpg.

 

 

nipper

[bfg9k]

My BEST mpg city is 19, worst is 18. My best mpg highway is 24. This is significantly off from the EPA estimates by about 20%. This is calculated using the method of filling up and dividing by miles driven since last fillup.

 

I have the identical problem to you (and have started at least one thread like this one which you've probably read!). My '98 Legacy L wagon with the 2.2L, 1-year old Nokian NRW tires, and a rebuilt 4EAT gets 21-22 mpg highway traveling between 60-70mph.

 

I have: cleaned the MAF, changed the air & fuel filters (OEM), have new plugs & wires, a new front O2 sensor, tried synthetic gear oil (Royal Purple 75w90) in front & rear diffs, tried synth oil in crankcase (pennzoil plat 5w30), semi-synth ATF (Specialty Formulations Autoglide) in the tranny, and maybe one or two more things I can't recall.

 

Benefits of all this: synthetic gear oil helps with steering effort in low temps , same with using synth ATF (I use Royal Purple MaxATF) in your power steering. The Autoglide stuff makes the tranny shift very nicely. No difference with synth oil, except for louder startup piston slap. Havoline dino 5w30 makes the engine run nice & smooth and is just $1.40 a quart. ZERO effect on mpg's, unfortunately.

 

Oh yeah, I'm in the midst of an AutoRX cycle (www.auto-rx.com) to clean out the engine and see if that helps. So far, nothing to report.

 

About the only things I haven't tried are ultrasonic cleaning of the injectors and replacing the rear O2 sensor. I came across a post recently that claimed the REAR sensor is the culprit for the gas smell when cold: http://www.ultimatesubaru.org/forum/showthread.php?t=43624&highlight=outback+sport

Easy diagnostic on the o2 sensors, if you are bogging down and shuddering on the low end, but dissappears with higher RPM's... Most likely o2. If you get bogging all over, fuel issue. But, if you can idle INSIDE an OPEN garage for about 20-40 seconds, shut off, get out and smell gas... You prolly need some new o2 sensors.

 

Also, some people around here are under the impression that only replacing the front o2 sensor will quell your probs... They are mistaken. I tested that theory on a couple of tanks of gas. Save your self the time, $$$, and trouble and do both at once. OEM ONLY FOR THE REAR.

Once my work bonus arrives just before Xmas I will invest the $85 in an OEM rear O2 and see what happens.

[wqbang]

Actually with that weight load, thats not a bad mpg.

 

 

nipper

 

But how do you explain the 18 in the city with one passanger and an infant?

[nipper]

hehe HEY im not perfect

 

like i said what kind of tires are you running. Tires can have a big effect on milage, and what pressure are you running them at.

[HooptyGL]

hows your flow? after i put a bigger intake in and did borla 2.5 from the headers to the tail i noticed about 4 mpg difference. maybe your cat(s) are shrapnel and causing your pipes to choke the flow.

 

just a thought.

 

neal