"Bouldaru" (alphadogg14)
04/13/2015 at 15:37 • Filed to: Jdm
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"Bouldaru" (alphadogg14)
04/13/2015 at 15:37 • Filed to: Jdm | 1
| 9 |
The dreaded subaru check engine light. I was driving 7 people including myself in my outback (it seats five) and I was coming up a hill going into Golden (Colorado School of Mines was partying hard and I designated drove for my friends who paid me). I was doing 60 in fifth gear with cruise control on and I didn't realize how much throttle CC was giving the engine until revs started dropping. Then the CEL came on. So I shifted down to get more torque so I could make it up the hill. I continued on hwy 93 until I got to golden driving the speed limit. I experienced a loss of power but I attributed it just to the ~1100 extra pounds I was carrying. So I dropped them off in golden and drove to Denver and power seemed normal. When I got home my brother helped me pull the air filter, which had burned oil on it right where the MAF sensor is. The airbox had some blow by in there. So as it was 11:30pm the only place carrying auto parts was Walmart. My brother drove me to walmart and we picked up a new air filter and some MAF cleaner (and some goldfish for my drunk friends to munch on). I sprayed the shit out of the sensor and airbox and let them dry and then reassembled the intake. I drove to pick up my friends and was careful not to go full throttle. So I parked it overnight and in the morning the CEL was off. I pulled a P0420 code in the morning.
Any ideas what happened?
Textured Soy Protein
> Bouldaru
04/13/2015 at 15:44 |
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Your car has oxygen sensors before and after the catalytic converter to measure proper function of the cat. Likely causes are:
1. Bad oxygen sensor(s) causing erroneous readings and making the ECU think the cat is fouled up.
2. Bad catalytic converter. It could either be getting old in general, or can get fouled up by periodic misfires or running too rich or too lean.
crowmolly
> Bouldaru
04/13/2015 at 15:47 |
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P0420 usually means you were running like an antelope; out of control.
All joking aside, it means the cat wasn't working properly or the rearmost O2 is on the fritz.
Since you know that you were using the car well outside the norm I'd:
1.) Change the air filter (looks like you did this)
2.) Clean the MAF and oil out of the intake system (looks like you did this too)
3.) Check the PCV valve
If everything seems OK, clear the code and see if it comes back. Any smoke or smells out of the tailpipe?
How old is the car? Maybe the PCM was dumping gas to get the heavy car up a steep hill and that killed the cat/O2?
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Bouldaru
> crowmolly
04/13/2015 at 16:01 |
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It's a MY2001 built in June 2000. So 15 years old. No smells or smoke coming out of the tailpipe. How do I check the PCV and PCM? Also what do those valves do?
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crowmolly
> Bouldaru
04/13/2015 at 16:08 |
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Don't worry about the PCM. That's the "powertrain control module", or car's computer. I was commenting on how it was probably doing everything it could to make power.
The PCV is the positive crankcase ventilation valve.
http://www.scoobymods.com/showthread.php…
http://www.aa1car.com/library/pcv.ht…
If yours has never been changed and it's bad it could lead to blowby.
CaptDale - is secretly British
> Bouldaru
04/13/2015 at 16:18 |
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We get a lot of Subarus in our dealership that need the cat replaced. There is some extended warranty or recall thing that brings in a lot of older Subarus for cat replacement. Maybe look into that?
RallyWrench
> Bouldaru
04/13/2015 at 16:24 |
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PCV is Positive Crankcase Ventilation, the engine's breather system for oil vapor & crankcase pressure. Its valve is dependent upon engine vacuum to operate properly, and under high load there is none, and the engine is simultaneously producing more internal pressure. The valve could also be coked up with oil deposits, so it's possible it was overwhelmed & belched some oil into the intake at a higher than normal rate. That would then have found its way through the engine to the Oxygen Sensors, Cat and post-Cat monitor sensor, possibly contaminating or cooling them & affecting the readings.
The PCM is the Powertrain Control Module, otherwise known as the ECU or ECM. Under high load, it is increasing the injector pulse to provide more fuel.
Subarus like to throw Cat codes on a regular basis once they have some miles (my '01 Outback included), and I usually clear it & try to set the monitors, then see if/when it comes back. It can be days, weeks, or months sometimes because it's likely only in a certain temperature range that the Cat is weak. If the PCV is operating properly, the MAF isn't contaminated, and there are no exhaust leaks, 02 sensors are the first step.
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Bouldaru
> crowmolly
04/13/2015 at 17:35 |
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I went to a Subaru-only shop (not a Subaru dealer but they only work with subies) and talked to a mechanic. He told me exactly what you said; that the PCV should be replaced. I'll definitely replace it if it throws another code. In the meantime I'm going to change the oil and oil filter (pretty sure it's running conventional oil and I'm coming up on 3k miles so it's a good idea anyway)
Denver Is Stuck In The 90s
> Bouldaru
04/14/2015 at 11:57 |
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I need to replace my pcv as well, we can do both of ours together when we do your oil change
Jake Huitt - Two Alfas And A Nissan, Not A Single Running Car
> Denver Is Stuck In The 90s
05/07/2015 at 12:15 |
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Come to the lift. Double oil change and pcv is 4 hours tops.