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Hello, this is my first post here.

My wife has a 2001 subaru outback 4cyl/2.5L AWD that has been running funny for a couple years now. The knock sensor has been on for about a year. Shes been complaining that it is starting to run "worse" so I drove it for a bit. It slips when you mash down on the gas pretty bad--but seems to get better as the car heats up. This problem has been going on and off for years and I've never been able to get it fixed right. I've even flushed the transmission, no fix.

This morning I couldn't get it to start and realized she had left the lights on. The batter was shot so I changed that out, but was getting a blinking CEL. Pulled the codes and got a whole lot of them!

p0133--O2 sensor
p0328--knock sensor
p0340--CMP sensor
p0710--transmission fluid temp sensor
p0301-304--misses on all four cylinders

When you stop at a red light, the idle goes down real low almost like it going to shut off. Giving it gas cold when you are driving looses power and it slips real bad.

The plugs and wires are about 6 months old (changed them this summer). Fluid and oil levels are all okay. Cleaned the IACV this summer. Tranny was last flushed about a year and half ago. Wiring all seems okay, no changes when I jiggle it around. Checks out with the multimeter.

I know coil packs aren't supposed to go bad often on subarus, or so I've heard, but I'm wondering if it has. This is where I am thinking about starting this journey to get this thing running okay again, does this sound like a good place to start? Any suggestions?

Thanks
 

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1999 Outback Wagon Green 2.2 swap
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50 Posts
I don't really have an answer for you but a couple of questions that if answered may help someone else help you.
Did all or any of these things, besides the knock sensor, show up right after the battery change? If not how long has it been doing this and was it a gradual progression?
I can say that when I had my 98 Impreza RS i had a similar thing happen when I changed the battery out, not the same though. When I came to a stop it would almost die then the idle would shoot up to around 2k and back down again. I unhooked the battery, stepped on the brake pedal for around 10 seconds, and then hooked it back up, all was corrected. I don't know if the whole brake pedal thing really does anything but I was once told that it will clear some of the memory in the computer.
If yours is running rough and the engine light is flashing I have always been told that is due to an active misfire. That could be due to a bad coil, bad plug wires, bad plugs, etc.
Sorry that I can't say hey this is what it is but maybe someone else will be able to.
Good Luck.
 

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Premium Member
2001 VDC/SC One of a Kind
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14,436 Posts
For starters, you can't leave the lights on unless the key is on. When he key is off power is off to all accessories and headlights.

It sounds like a loose ground. Recheck the battery cables, the ground wire at the left fender, the one on top of the intake toward the back on the pass side and the ones to the firewall.

Get a new knock sensor. Use a Subaru sensor.
 

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'14 3.6R Outback
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For starters, you can't leave the lights on unless the key is on. When he key is off power is off to all accessories and headlights.

It sounds like a loose ground. Recheck the battery cables, the ground wire at the left fender, the one on top of the intake toward the back on the pass side and the ones to the firewall.

Get a new knock sensor. Use a Subaru sensor.
So they changed that on a GEN4? I can turn on my lights, when the car is off.

It would require that someone use the switch AFTER I shut down. I think that's what you meant right?

Hello, this is my first post here.

My wife has a 2001 subaru outback 4cyl/2.5L AWD that has been running funny for a couple years now. The knock sensor has been on for about a year. Shes been complaining that it is starting to run "worse" so I drove it for a bit. It slips when you mash down on the gas pretty bad--but seems to get better as the car heats up. This problem has been going on and off for years and I've never been able to get it fixed right. I've even flushed the transmission, no fix.

This morning I couldn't get it to start and realized she had left the lights on. The batter was shot so I changed that out, but was getting a blinking CEL. Pulled the codes and got a whole lot of them!

p0133--O2 sensor
p0328--knock sensor
p0340--CMP sensor
p0710--transmission fluid temp sensor
p0301-304--misses on all four cylinders

When you stop at a red light, the idle goes down real low almost like it going to shut off. Giving it gas cold when you are driving looses power and it slips real bad.

The plugs and wires are about 6 months old (changed them this summer). Fluid and oil levels are all okay. Cleaned the IACV this summer. Tranny was last flushed about a year and half ago. Wiring all seems okay, no changes when I jiggle it around. Checks out with the multimeter.

I know coil packs aren't supposed to go bad often on subarus, or so I've heard, but I'm wondering if it has. This is where I am thinking about starting this journey to get this thing running okay again, does this sound like a good place to start? Any suggestions?

Thanks
First, some of those codes could be stored from however long since you last had a code. The flashing code light means you have an active code happening "right now."

Knock sensor isn't to hard to replace. I agree with Cardoc, replace it and make sure it a Subaru one. I'd then clear the codes and see what comes next. A bad knock sensor could be your only problem.
 

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03 H6 OBW & 06 WRX Sportwagon
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how many miles and when was the timing belt chnaged? the p0340 code is worrisome and slipped TB might explain powerloss.

but yeah, start with a clean slate and see what codes come back, but, I'd be tempted to have the TB timing checked before continuing to run the car very much.
 

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Premium Member
2001 VDC/SC One of a Kind
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14,436 Posts
His is a Gen 2 by the title. So, lights go out with the key off.

The codes he posted were after the battery replacement, so they all popped up together. When this happens, ground issue. Most likely the ground lug on the intake corroded or loose, but could be loose at the battery and would be a good start since the cable was removed for a new battery.
 

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Onyx, 2008 LL Bean 3.0R and 2017 Honda Civic Hatchback Sport Touring
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Ground or alternator. Alternator failure may be why the battery died, since it was impossible for it to be the headlights. Alt can cause many of those symptoms and weird unrelated codes as well.BTW, my coil went bad and replacing it solved a lot of problems with the way the car ran as well. Both can be checked fairly easily.
 
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