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1998 Forester fuel economy


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12 replies to this topic

#1 Mr. Carb

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Posted 14 July 2014 - 11:13 PM

I've done a lot of searching but really haven't found much information.  It appears most solutions to the fuel economy question has been that it's just normal after age.

 

So, I have a 1998 Forester S, EJ25D with the auto transmission with the clock at 234k miles.  The car gets about 20mpg on the highway, around 14-16mpg around town. It's only about 1-3mph better than my old 6.9L Chrysler.  The previous owner is a family friend so when he tells me it averaged 24-26mpg before it broke I believe him.  Bought the car for cheap because headgaskets were blown (combustion chamber to coolant passage). With help from friends I replaced the headgaskets and all the associated gaskets with it. I suspect something may have been missed, or possibly done wrong that could have comprimise the fuel economy. So anyway, here's what I have replaced, checked etc:

 

Torque bind - was repaired

Spark plugs, wires, pcv valve, timing belt, timing belt pullys (tension and idlers), tires, front O2 sensor, fuel filter and air filter replaced.

I've cleaned the MAF with MAF cleaner and ran seafoam in the gas tank.

Replaced cracked and broken vacuum/crank ventalator hoses and checked for vacuum leaks.

 

No engine check light or codes.  Does anyone know of anything else that I can check before spending hundreds on more parts? or to find out if I need to buy more parts?  I'm kind of suprised that even though it's a smaller lighter car than the 2001 Outback I used to have, it does worse on gas, even with the same sized engine.  I'm wondering if maybe the cat is gummed up from when the car had blown head gaskets.

 

Any ideas would be great to hear, thanks! :)


Edited by Mr. Carb, 14 July 2014 - 11:17 PM.


#2 Fairtax4me

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Posted 15 July 2014 - 10:09 AM

Those aren't known to get great mileage but should be a little better than that. 24-26 should be attainable if driven conservatively.

Head gaskets will foul O2 sensors. Did you replace the front sensor? If so, what brand?

What brand of spark plugs did you put in?

#3 grossgary

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Posted 15 July 2014 - 10:36 AM

1.  what kind of driving are you doing?  

are you doing long 60 mph stints?  if you're doing lots of city driving or highspeed interstate the mileage will suffer.

 

fuel injectors, valve clearance?

 

compression and leak down test it.

 

removing the roof rack and lowering it will help.



#4 Gloyale

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Posted 15 July 2014 - 10:50 AM

I've done a lot of searching but really haven't found much information.  It appears most solutions to the fuel economy question has been that it's just normal after age.

 

So, I have a 1998 Forester S, EJ25D with the auto transmission with the clock at 234k miles.  The car gets about 20mpg on the highway, around 14-16mpg around town. It's only about 1-3mph better than my old 6.9L Chrysler.  The previous owner is a family friend so when he tells me it averaged 24-26mpg before it broke I believe him.  Bought the car for cheap because headgaskets were blown (combustion chamber to coolant passage). With help from friends I replaced the headgaskets and all the associated gaskets with it. I suspect something may have been missed, or possibly done wrong that could have comprimise the fuel economy.

 

Buckets mixed up for vavles?  that would make some valves tight and others loose.......either way not good for milegage.

 

Also.....Different people drive different.....and people's perception of the mileage they are getting is often not the actual "by the numbers" mileage figure.

 

I'd check compression, and run Lucas Fuel injector treatment.....that will help some....but honestly I think the EPA only rated that car at 18 city and 24 hwy  (avg. 20)  NEW.



#5 Mr. Carb

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Posted 15 July 2014 - 09:34 PM

Replaced front O2 sensor with a bosch.  Plugs are NGK.  Idle is rough when the car is stopped and in gear at times, smooths out when I put it in neutral. For some reason the extra load of the transmission makes it rough. (not the brake booster as it does it even when using the parking brake to hold the car in place while in drive.) When the car is at full operating temp the rough idle isn't as common.

 

Mostly freeway 60-70mph, rpm's vary from 2500-2800 rpms depending on what range of speed I am driving on the freeway.  Only about 20 miles of around town driving per tank of gas, rest is on the freeway (180-220 miles or so).

 

We actually did not remove the valves or lifters at all, to avoid getting them mixed up or back in the wrong spots.  Compression, valve clearance have not been checked.  That seems like a lot of work to get 3-4mpg back.

 

If that's really the "average" for that car on the highway, I'm kind of bummed.   Maybe I'll try an early 90 ej22 long block swap when I get bored.

 

I'm pretty sure it's not driving style, as I said, the 2001 outback got 25-28mpg on the freeway when I drove it, my old 86 XT turbo did about 32mpg average driving on the same commute route.

 

Given how unfimuliar I am with fuel injection tuning I was hoping that maybe there was something minor I missed that could cause a rich fuel mixture. If not, then I guess it is what it is.



#6 86BRATMAN

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Posted 15 July 2014 - 10:03 PM

The coolant temp sensor could be on its way out. my buddy's ej22 swapped 97 Legacy gt was getting similar mileage to yours after we swapped it due to a completely fubar'd ej25d. He chased all kinds of stuff for aboutb2 months before he finally listened to me and replaced the sensor. During this time his mileage degraded to about 12-14 highway. I replaced the sensor and it went back up to the upper 20s.

if the coolant temp sensor is bad it won't usually trigger a cel, it just tells the ecu the motor is very cold and it dumps loads of extra fuel in to "warm" post the engine up. On your motor there will be two, one single wire sensor for the dash guage and a two wire for the ecu. It's the two wire one I'm talking about. Removing the idle air control valve will provide pretty easy access to the sensor.

#7 Mr. Carb

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Posted 15 July 2014 - 10:23 PM

That makes total sense! I wasn't sure if they were seperate for the gauge and ecu or not.  I know where the ecu one is because we forgot to plug it in initially when we got done with the headgaskets.  I'll try a new one of those and see what happens.  I will report back with info and if that solved the problem.



#8 1 Lucky Texan

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Posted 15 July 2014 - 11:05 PM

Idle is rough when the car is stopped and in gear at times, smooths out when I put it in neutral.

 

that's the front axles - known problem 99% due to aftermarket rebuilt/new chinese axles. Re-booted used (or new - $$$$) Subaru axles will probably be the only fix for that.

 

Knock sensor could be bad.



#9 Mr. Carb

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Posted 16 July 2014 - 12:52 AM

that's the front axles - known problem 99% due to aftermarket rebuilt/new chinese axles. Re-booted used (or new - $$$$) Subaru axles will probably be the only fix for that.

 

Knock sensor could be bad.

 

Knock sensor is new, OEM. Forgot to add that to the list of new stuffs.   I do know one of the front axles clicks sometimes, and I have records that it was done at a none subaru repair shop, so probably aftermarket.  When I'm bored I'll get an OEM axle and replace it.  I'm assuming they arn't any different to do than the ea81 series subarus were.

 

Anyway picked up a new coolant temp sensor, I'll probably install it tomorrow or Thursday, will report back once I've gone through a full tank of gas on the new sensor.



#10 Mr. Carb

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Posted 16 July 2014 - 12:57 AM

For the record, the original brochure that came with this car states 21mpg city, 26mpg highway, so it's not even doing the city economy it's advertised to do.



#11 Gloyale

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Posted 16 July 2014 - 11:09 AM

Yeah....the brochure is Fuji Optimism......

 

They don't get that kinda mileage unless you are "hyper-miling".......driving less than 65mph on freeway and accelerating very slow and steady in city......never more than %30 throttle opening.  Who drives like that?

 

Here's the EPA page

 

http://www.fuelecono...mes/14773.shtml



#12 Gloyale

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Posted 16 July 2014 - 11:19 AM

We actually did not remove the valves or lifters at all, to avoid getting them mixed up or back in the wrong spots.  Compression, valve clearance have not been checked.  That seems like a lot of work to get 3-4mpg back.

 

How did you keep all the buckets in their bores?  Even if the buckets stayed in......didn't some shims fall off???  You didn't send out the heads for surfacing?

Valve clearance would have been easy to check while heads are out.

 

One more thing to remember is the 2001 legacy had an updated ECU system, and a SOHC 2.5......Not the DOHC......and 2001 Legacy is much less boxy, more areodynamic than Forrester.



#13 Mr. Carb

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Posted 19 July 2014 - 05:44 PM

How did you keep all the buckets in their bores?  Even if the buckets stayed in......didn't some shims fall off???  You didn't send out the heads for surfacing?

Valve clearance would have been easy to check while heads are out.

 

One more thing to remember is the 2001 legacy had an updated ECU system, and a SOHC 2.5......Not the DOHC......and 2001 Legacy is much less boxy, more areodynamic than Forrester.

 

We were very careful.  :-)  We did take a straight edge to the engine block and heads and everything looked good. Didn't have anything machined.  Headgaskets are working as far as coolant and oil goes, so I don't think it's an issue.

 

At anyrate, I do drive very light on th gas pedal, if I really push it (no heavy accel at all on the entire tank of gas) I can squeeze about 21mpg out of a full tank. That includes keeping the speed under 65mph, etc.

 

I just replaced the coolant temp sensor, and took the car out to get it topped off on gas (it was at 1 quarter). The idle and acceleration is already feeling better than it did before today's work.  We'll see how this tank of gas goes and I'll report back.  Old coolant temp sensor was very corroded.  Also found that the little Y plastic fitting for the PVC plumbing (one hose to the air intanke, other to the pvc valve) had so much oil hardened dirt in it that one of the fittings was completly blocked. Cleaned the heck out of all that too while I was at it.






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