Terrible fuel economy and check engine light on

[AEROCOOK]

After a year of sitting in my garage I finally got my 97 Legacy Outback wagon on the road, it's an automatic with the 2.5 motor.

In order to licence the car, I had to have an emissions test done and the car passed all 3 categories on the test with flying colours. Although the car seems to be running well, the check engine light is on and the fuel economy is terrible, around 400 kms to a tank. I scanned for DTC codes and came up with P1101 P0400 and P0141. Im not clear on code P1101 but I know that P0400 is EGR flow malfunction and P0141 is O2 sensor heater circuit malfunction bank 1 sensor 2. I was told that this O2 sensor would not affect fuel economy if it went bad, but at 400km / tank, I have to question that theory.

Any thoughts or advice?

[Fairtax4me]

P1101 is Neutral switch circuit, Off.

 

That could be the inhibitor switch (park/neutral safety switch on the transmission selector shaft), or a wiring issue.

 

That specific circuit of the O2 sensor won't directly affect fuel economy. As a matter of fact the rear sensor (which this code applies to) doesn't have any input in fuel control at all.

That's not to say the front O2 sensor isn't causing the problem. It may be slow due to age or clogged or damaged from sitting but just isn't throwing a code yet. Testing the sensor might reveal it is faulty.

 

I might check the rear sensor to make sure it is it's a break in the heater rather than a power delivery problem, (maybe a mouse chewed some wires) but I probably wouldn't bother to replace it unless you get a P0420 code out of it, or it becomes an issue for future inspections.

[Cougar]

The P1101 code refers to the inhibit switch for the transmission. Cleaning the contacts of the switch may clear the trouble. The code for the O2 heater may be due to a bad connection to the heater circuit or the heater itself is bad. Ohming the heater leads will tell the story about that. The code refers to the sensor after the CAT.

[Olnick]

Might help your fuel economy if you do some general tuneup--oil & filter, fresh ATF, air & fuel filters, new plugs & wires, new PCV valve and clean connecting hoses, clean MAF & IACV, check vacuum hoses, throw some Techron in the gas tank, maybe Seafoam the top end.

 

How many miles on the car? Might be time to change the front O2 sensor anyway.

 

Check your brakes too. They could be dragging a bit--make sure the sliders are properly greased.

 

Good luck and let us know how it goes.

[AEROCOOK]

Thank you for the replies. I didnt want to be too long winded in my original post so I didnt get into details about recent repairs etc. but I will do so now... Brakes rotors and pads front and rear are new including 1 rear caliper that was dragging, all is well now. Transmission fluid is new as I had to replace the lever for manual valve in the valve body. I also replaced the shifter cable and had the inhibitor switch off during that repair, I know that it is out of adjustment by a little bit because sometimes I have to give the shifter a nudge forward to get the car to start. (Would that cause P1101?) The car has 322,000 kms on it so a tune up is warranted and I will be doing it this week. I have a can of seafoam and would like some tips on how to use it, can anyone offer advice? The P0400 code has me puzzled, I manually depressed the diaphram on the valve and the idle went way down which leads me to believe that the EGR tube is not plugged, so I dont know whats triggering the code.

[Cougar]

What would cause the P1101 code? The answer is refered to in post 3.

 

For the P0400 code the EGR valve may be leaking, not plugged. Try cleaning the valve to see if that helps.

Edited June 22, 2010 by Cougar

[Leg91LS]

I've learned to replace the O2 sensor every four years, no matter what. My 91 LegoLS gets 21 mpg in city driving with an automatic and AWD with 217K miles.

[nipper]

O2 sensors can get tired without throwing a code.

 

How old is the timing belt (time and mileage))?

 

Do a real tuneup and replace the pcv valve.

 

Check tire condition and look for a stubborn brake slider. Check that the parking brake is not draging (especially after sitting).

 

What exactly is poor gas mileage and what kind of driving do you do?

[AEROCOOK]

O2 sensors can get tired without throwing a code.

 

How old is the timing belt (time and mileage))?

 

Do a real tuneup and replace the pcv valve.

 

Check tire condition and look for a stubborn brake slider. Check that the parking brake is not draging (especially after sitting).

 

What exactly is poor gas mileage and what kind of driving do you do?

 

I have no Idea how old the timing belt is so that is definately on my "To do" list. I have checked and can confirm that the brakes are not dragging and the parking brake is not dragging either. Tires are new and properly inflated. I plan on doing a complete tune up including PCV valve and new timing belt in the very near future and after a few fill ups I will let you all know if there is an improvement. BTW do you know how to decarb using Seafoam? I have a can but Im not sure on how to get it into the intake.

[Olnick]

When you replace the PCV be sure to remove the hoses that connect to it and clean them thoroughly--or replace them. They can get really gunked up.

 

For using Seafoam try a search, there have been numerous threads over the years. Here's an old one that covers a lot of ground:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=42623&highlight=seafoam

 

Good luck.

[Allpar Mod]

I Seafoamed my '99 OBW like was suggested in the past thread. Two things:

 

* It'll suck the can dry very quickly. Be ready for that.

* The smoke is impressive. Your car will look like something from a James Bond picture for a while until all of the Seafoam is burned up. So, don't do it in a garage. If you live close to your neighbors and like them, you might want to wait until they're gone to work or something.

 

My O2 sensors seemed to have survived ok. I did this last fall after I bought it and have seen no ill effects since.

[nipper]

Seafoam. If you like your neighbors go somewhere unpopulated to do it. If you hate them point your tailpipe at them.

 

[Olnick]

* It'll suck the can dry very quickly. Be ready for that.

 

True! Get a small, clean container like a yogurt cup and put the required amount in it.

 

 

*My O2 sensors seemed to have survived ok. I did this last fall after I bought it and have seen no ill effects since.

 

I've done it to several family cars over the years--never had a problem with the O2s.

 

Good luck. Enjoy the show!

[Fairtax4me]

I use a long vacuum hose (about 3 feet) attached o the nipple that sticks straight up on top of the intake manifold. Put the can where it won't tip over, dip the vacuum hose into the can and "slurp" about a half a can out with one hand while you feather the throttle with the other to keep the engine running.