any ideas would be great! 97 legacy outback, 5spd. was getting 28 on high way, now getting 18. had a check engine code for cat, so removed it and cleaned o2 sensors, had a misfire, fixed plug wire. gas milage had been deceasing for 6 months then hit bottom. Any sugestions?

I suggest you replace all spark plugs and the wires. Also, replace the EGR valve. I would also run a can of Chevron Techron injector cleaner through the gas tank.

 

Did cleaning the 02 sensor remove the CEL code? The misfire over an extended period of time may have damaged the 02 sensor.

if it threw a code for the O2 sensor, go get a new one and replace it - seriously. you can get a direct fit replacement (Denso) for about $65.00 from Advance Auto - or Bosch Premium for about $100 - look it up. (personally, I stay away from the ones that have to have the plug end spliced in - just asking for trouble with those IMHO)

 

I went from an average of 24-25 mpg to hitting 30 mpg by replacing mine.

 

Also, do a basic tune up - plugs, wires, air filter, etc

just checking, but the removal of the cat won't cause problems?

just checking, but the removal of the cat won't cause problems?

 

he didnt remove the cat - he removed the O2 sensor & cleaned it.

any ideas would be great! 97 legacy outback, 5spd. was getting 28 on high way, now getting 18. had a check engine code for cat, so removed it and cleaned o2 sensors, had a misfire, fixed plug wire. gas milage had been deceasing for 6 months then hit bottom. Any sugestions?

 

 

Put the cat back, as that is rarely an issue, and will usually result in rattles and a loss of power. You can not clean O2 sensors, you replace them. They are not meant to last forever. The front one is OE the rear can be generic. In the future do only ONE thing at a time as it makes it tough to diagnose. The front one does all the fuel manegment the other checks the cat.

 

Do not do a laundry list of items like listed above, that is just throwing money away. Start with a good tuneup and the O2 sensors. Use OE wires and OE recomended plugs.

 

How old is the timing belt.

timing belt, head gaskets, water pump, plugs, and clutch were all done this past summer, 16k ago. used ngk plugs!

used ngk plugs!

 

Those must be some spark plugs if getting them used warrants the use of an exclamation point!!! How much are they new?

timing belt, head gaskets, water pump, plugs, and clutch were all done this past summer, 16k ago. used ngk plugs!

 

i do not see a pcv valve (just a good idea to do it every three years), fuel filter, ignition cables, and i will assume the air filter has been done.

 

I am sticking with draging calipers, and my second would be a dying O2 sensor.

 

How well is it starting in winter ?

Haha , no the plugs were new, was just saying the brand i used was ngk. my mistake. also has new egr, fuel filter, brake pads (rotors seemed ok, and everything was free moving.

Starts fine, that is when i found the mis fire though, and replaced the wires. not sure if the coil pack might be going too, is there a real good way to check the packs?

Thermostat?

replaced thermostat too

replaced thermostat too

 

With what?

Do another highway run (pure highway) and a purely mathmatical MPG figure. Try to stay around 60-65 (over 70 the MPG really takes a dump) and let us know what you come back with. At 18mpg on the highway, you should be getting like 10 around town. You would be seeing CEL lights and smelling rotten eggs or unburnt fuel etc

 

 

Since you have plenty of power I am going to discount the collapsed exhaust pipe.

 

Hrmmm .........................

 

How old is your clutch?

replaced thermostat with oem

clutch was done this past weekend due to the last one i put in being advanced auto clutch and one of the springs fell out of the clutch plate replaced with Sachs Clutch Kit

 

exhaust pipe is free breathing

 

since i have cleaned front o2 sensor there has been no cel for a week.

 

i drive a total of 100 miles a day round trip to work and it is all highway i always to the mathimatical way of figuring gas mileage. I have been averginge 17 mpg

between fill ups approximately 170 miles on 10 gallons of gas, i don't even get 2 full days of driving without filling up

Aproxamitly?

 

You do the gallons purchased divded into the miles driven.

 

We havent mentioned the obvious, my fault. Tire condition and pressure?

 

WHat has the air temp been?

correct with the mpg calculation.

tires are new as of 3 months ago, not aggressive all weather, tire pressure is good.

good heat in car, 20s outside, weather conditions haven't changed as the mileage has.

Then i am going with the Engine Temp sensor, though i really really do no believe in cleaning O2 sensors, I think that is the issue, but a CTS is much cheaper. Since I do not have the car in my driveway I cant tell. NO I change my mind, lets replace the front O2 sensor. They wont always throw a code if they are getting sluggish.

 

Have you put a scanner on this to make sure it is going from open loop to closed loop?

I replaced the engine temp sensor 3 months ago (can't remember the exact reason). I did replace coil pack this week, due to a misfire on every cylinder.

Runs somewhat better, but not as it should be. Do you think replacing the front O2 sensor will make a huge difference with out the cat being in there (even though removing the cat was a suggestion from a friend I do not believe that was a good choice, these cars need the cat to run right don't they)? I have thrown a scanner on it (keep it in the car) but I am not sure what menu to go into to see if it is in the closed loop.

 

I'd do a New O2 sensor before anything else...at this rate you're losing over 20-25 bucks a week in gas money. You have already done everything else I'd do. You can see the sensor voltage and fuel trim ratios with your scanner depending on the type you have.

 

cheers

I guess we don't need to worry about this any more. I traded it in on a automatic 2007 impreza. thanks for all your help guys!