O2 and Knock sensors

[lefty2053]

Trying to figure out what all this Subie needs. Took it for a ride around a 3 mile block. Ran good until it warmed up. Then it started to spudder and if I gave it much fuel ti would die.

First off the O2 Sensor Bank 1 Sensor 2 Malfunction Also Knock Sensor Malfunction.

Questions are: Can either of these cause the car to run that way? Run good until warmed up? Sorry I am no mechanic but try to learn something new all the time. I know neither of these are expensive but I would like to know if they can cause the poor running.

 

So far I found it needs:

2 tires on back to match the fronts.

Knock Sensor

O2 Sensor

Front Drivers side CV shaft

Muffler with some pipe

Spare tire

Jack

Every thing else seems to work well. No leaks of oil nor Tranny fluid.

 

I figure I can get everything for around $400 or less. I have about $600 in the car from the trade of an ATV.

I just don't want to put too much into the car as it will be just a spare car for when a family member has a break down.

 

Thanks for any help.

[porcupine73]

Hi. What model and year? (Good to include in any post asking for help since advice can vary based on that info).

 

I'd probably start with the knock sensor. If it has a code for that, it is retarding the timing to the maximum in its map. I have driven a couple soobs when that code comes on, and it really makes it hard to drive them, almost dangerous I would say. Absolutely zero power and often feels like it is going to stall out.

 

Knock sensor code is often the knock sensor itself, but could also be wiring or other issue. Ditto on oxygen sensor codes. Your oxygen sensor code sounds like it is for the rear?

 

Tires must match within 1/4" circumference, so there isn't a whole lot of room for existing/old tires on front or rear. People often say in this case to mix them up, one old and one new on the front, ditto on the rear but on opposite sides. That supposedly works with open diffs anyway. If it's an auto could put FWD fuse in until tire issue is addressed.

 

Oh if you are getting tires anyway, could maybe just keep one of the old ones if you can find a spare soob wheel to use. It probably won't fit neatly in the spot for the thin spare though.

[Rooster2]

It would be helpful to know what year and model car this is. If it is a '95 or newer, it would be OBD 2, and you could take it to an auto parts store, where they could pull the codes, if there are any. Pulled codes would tell you if the knock sensor or 02 sensors are reading bad.

 

My experience with a bad knock sensor, is that my car still ran good, but was noticeably down on power. With a bad knock sensor, the computer goes to running in "limp mode," by that I mean that the computer electronically retards the timing to prevent detonation or ping. The retarded timing prevents the engine from putting out max horse power. This said.......I doubt it is the knock sensor causing severe driveablilty when engine is warmed up.

 

I am thinking this is more likely a problem with the MAF or MAP sensor. Someone in a recent post was having a similar problem. You may want to read that post and responses.

 

Since you said the motor ran well until warmed up, I am thinking there isn't that much wrong with the motor. Others will chime in, but I am thinking it won't cost much to fix the driveability problem.

[1 Lucky Texan]

just putting in the possibility of temp sensor. Could allow good running at 'true cold' start, but over-rich when warmed up. Might not throw a code.

[lefty2053]

This is a 1997 Legacy GT Automatic.

 

The Codes are P0141 For the O2 Sensor and P0325 for the Knock sensor.

 

Both are Malfunction.

I will see if I can find the Knock sensor and see if it has the crack in it or a wire problem.

 

One thing I should mention is, after clearing the codes the O2 Sensor comes back first and then after driving it the Knock sensor code shows up.

Edited January 6, 2012 by lefty2053

[lefty2053]

OK I found the Knock sensor,can't tell much about it.

 

I also found the O2 Sensor(second one) is unplugged. Looks like they went on a very muddy road and might have pulled it out. I had to crumble the dirt off the connection just to see where the 3 wires went. I just need to know what wire goes where on that sensor. One black wire with copper connector and the other two are white wires with silver connectors.

 

The connection has one prong on one side with 2 on the other side of it.

Any ideas?

On a side note, the tranny looked like it might have been rebuilt as there was newer looking seals around it.