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rizzle84 01-23-2013 03:29 PM

MPG issues
Hey all-

I just got my 94 Wagon AWD Auto inspected and on the road after buying it a couple weeks ago. I started commuting to work in it this week (about 60 mi. round trip) and my mileage over the past few days is a really awful 18 or 19. All interstate pretty much too, NO city whatsoever (I live in the sticks). Is there something I can do to get that back on track? I'm not expecting hybrid mileage but 25 would be really nice. I checked air filter, looks old but not dirty. I just put new spark plugs in it too, Bosch platinum 2s. I'm wondering if it's some kind of O2 sensor or related intake/exhaust sensor. Any thoughts would be incredible

monkeyposeur 01-23-2013 06:37 PM

Check out the mpg sticky in the second gen forum:

I'd still replace the air filter. A good idea is to replace the air filter, fuel filter, all new plugs (I like NGKs), new wires, new pcv valve, clean the throttle body. Do you have any CELs? I get about 20-22 city and 27ish highway. Check your injectors, and ignition coil. Clean your MAF sensor too.

rizzle84 01-23-2013 06:58 PM

When I bought it I did have a CEL when the engine warmed up but after the spark plug change it hasn't come back on. I haven't figured out what the code was but it seems like it was a knock sensor. I'm wondering if the timing might be off. The engine for some reason just doesn't sound smooth, it feels kind of chunky but I know it isn't missing and there aren't any vibrations. I don't know what it' s supposed to sound or feel like because I've never owned a car with this engine. I know what an inline four would sound like out of time but this is new to me

rizzle84 01-23-2013 07:11 PM

Also, it does seem like it lacks a little power. I don't have anything to compare it to though but it feels like it could give more

snederhiser 01-23-2013 08:03 PM

First I would pull the codes that are stored in the memory before I would start throwing bucks at this. Sounds like your catalytic converter is starting to plug-up. If you ever had someone stick a potatoe up the exhaust pipe, you know what I mean. Usually I can tell by placing my hand at the exhaust pipe and checking for flow, another sign is that rotten egg smell. Maybe the muffler is coming apart inside blocking flow. Most muffler shops are going to install a universal cat and if you are handy so can you! Don't be lazy, check the stored codes first and troubleshoot from there. But my money is on the cat, Steven.

rizzle84 01-23-2013 08:07 PM

Would that affect the rhythm of the exhaust? Because it sounds uneven but doesn't feel wrong through any vibrations or anything like that

monkeyposeur 01-23-2013 09:20 PM

Start by buying a spray can of MAF cleaner. It may work wonders.

05LGTLtd 01-24-2013 09:20 AM

Does the transmission seem to be shifting OK? What are your RPMs Highway?

rizzle84 01-24-2013 10:04 AM

It seems fine. Around 2800 going 70 mph

mnstrmech 01-26-2013 09:50 AM

GET RID OF THOSE HORRIBLE BOSCH PLUGS!!!! they are a joke. Just get the NGK copper plugs that should be in there. Copper burns hotter, so you will get a more complete burn. Trust me on this one, Im an ASE certified technician.
Easy way to know if your cat is working is to look for moisture coming from the tailpipe, if you have moisture, your cat is working. Water is the by-product of a working cat.
18-19mpg in cold weather on the highway is fairly normal for your legacy. That was the mpg i was getting before i did a great mod that i will explain. Which brings me to your rpm's.
Next trip keep an eye on your rpm's. I learned about this myself. 2800 rpm's is a bit high at 70 mph. My 93 runs around 2400 fully warmed up. What i mean about this is the Subaru's ecu keeps the transmission out of torque converter lock-up (tcc lock-up) to warm the transmission fluid up faster, and takes a while before kicking it in. I noticed my tcc wont lock in for about 10 or so miles, KILLING my mpg's.
I posted in this post
on how to re-wire the "manual" button on the shifter to command the TCC on.

it was quite easy.... the "manual" button conversion i did a while ago is easy too. On the TCU module (under the dash, just next to the steering column), the one 20pin connector thats closest to the front, pin 6 is a blue w/ yellow stripe, that is the "manual" control. I snipped that wire, left at least 1 inch on the pin, and the other side of the wire i connected to a relay to turn the ground signal (which the other end of the blue\yellow wire runs to the switch, which goes to ground) into positive voltage. take the switched side of the relay that is positive and tap into the wire for the torque converter wire... which i believe is the red/yellow??? Dont quote me on that...
I should do a schematic for this.............................................. ...

"power" mode is easier.... i took the pin from pin 6 (the short 1" blue/yellow wire) and put that two spots over to pin 4... ran that to a switch that the other side is ground... so flip the switch... that pin see ground.... and power mode is active...... VOILA'!....... lol....

BTW.....IF you do the TCC switch mod..... DO NOT TOUCH THE "MANUAL" BUTTON ON YOUR SHIFTER TILL YOUR AT LEAST 40-45MPH!!!!! once you push the button... the TCC will kick in... and the amber "manual" light on your dash will light up....
I did this mod cause i drive on the highway about 20 miles one way to work, and i noticed the rpm's run about 2700 or so at 65... then when i was about to get off the highway... it was 2200... so i researched and found the tcc doesnt get locked up till it hits a certain temp,,, KILLING mpg.. so i went from approx 17/18 mpg to 25mpg by kicking on the tcc as soon as getting up to speed on the highway...... just got to remember to turn off the switch before slowing down on the ramp.......
if ya want pics... gonna have to wait...

Silly 01-26-2013 09:25 PM

Mnstrmech... This info regarding the TCC Mod is GOLD!! I have been trying to figure out how the TCC Locked and what was going on with the gearing on my '97 for some time. I had realized the same thing watching my tach. Thank You Very Much. Work is 35 miles for me, and almost all of it is highway, all down hill (one way it is anyway). Does it hurt the transaxle if you coast in neutral? From what I gather, as long as you rev match when going back into "D" it should be alright no?

mnstrmech 01-27-2013 09:11 AM

silly, you hit another great trick that i do.....coasting in neutral with an auto. I do it ALL the time, we have not a lot of hills, but enough. And once your exit ramp comes up just pop it in neutral and coast the whole way........... and you can put it back in drive ANY time you want, you wont hurt anything at all. As a matter of fact, i used to shut off my old car on this one hill(it was a manual), and coast the whole way, then when i slowed enough, i just put it in gear, release the clutch,and seamlessly keep moving.. lol
Someone asked about the TCC conversion, that was my write up. Maybe do a fresh thread on it?....

snederhiser 01-27-2013 05:46 PM

I do not believe that NGK has a copper plated core for their spark plugs. I think this is Champion marketing hype. I would use V-Power plugs, BKR6E-11(2756). I have heard that some bosch plugs do not work in certain engines? Have not seen this yet but usually go with manufacturers recommendations. Loved you lockout idea but would worry about increased cold pressure. Maybe a coolant bypass would be a good idea during the cold weather? Maybe using atf+4 synthetic fluid would help, Steven.

Silly 01-27-2013 10:00 PM

I have always coasted in my stick shifts, engine off, bump start when i would drop below 40 or so. The brake booster is the only thing I have found that could get damaged (using brakes long after all vacuum has been spent). there is about 3000ft in elevation difference from here to work. Lots of coasting opportunities.

Ihada147 01-28-2013 08:36 AM

I don't think it's a good idea to coast in neutral with an automatic, because the atf isn't being pumped everywhere including the propeller shaft, I mean if this is done all the time it could hurt the output area since there isn't any type of lubrication going back there and you'd have heat building up. Unless of course i'm mistaken about the way subaru auto transmissions work (which I probably am) isn't that the same reason they have to get dollies for the rear wheels when towing any car that isn't fwd or stick?

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