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'01 2.5. auto.
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Discussion Starter · #1 ·
***UPDATE WITH DIAGNOSIS AND SOLUTION ON 2ND PAGE****

Hey everyone, so i reset my computer by disconnecting the neg batt cable for a while, when i started it back up it ran like crap. Ok, the compy just has to "re-learn" so I let it idle for 30 minutes and drove it. After ~15mi it instantaneously ran perfect again. The next day, same thing; start up-run like crap-after 15mi its perfect. Well, now 3 days later, it's still doing it. the CEL is flashing and giving me codes:

P0301-cyl 1 misfire
P0302-cyl 2 misfire
P0420-catalyst efficiency

What the heck could it be? When it smooths out, it runs perfectly, just like it always did. But then after sitting for a few hours it will do it again. And again, it doesn't just "smooth out" over time, it's like someone is flipping a switch that says "function properly".

any ideas!?!?!?
 

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2000 Outback 5MT
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425 Posts
Strange, maybe your O2 sensor is bad and making the car run super rich or lean. Hopefully someone else will chime in.
 

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'01 2.5. auto.
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49 Posts
Discussion Starter · #3 ·
Strange, maybe your O2 sensor is bad and making the car run super rich or lean. Hopefully someone else will chime in.
i think there are diff codes for O2 sensors malfunctioning. But thanks, I hope I can get this solved.

I'm tempted to just throw in some new plugs and wires, but i'd rather not waste the money if I don't need to, as they aren't that old.
 

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1995 2.2 Auto Legacy Sedan
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142 Posts
Why did you reset it in the first place? I would check the items you worked on first if you were not already having problems as that would be the only thing changed.
 

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'01 2.5. auto.
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49 Posts
Discussion Starter · #5 ·
Why did you reset it in the first place? I would check the items you worked on first if you were not already having problems as that would be the only thing changed.
the oil was running low so i topped it off and accidentally overfilled it. The CEL came on and i figured it was because of that, so i just reset the compy after draining it down. then all this began...
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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18,665 Posts
several things come to mind, not sure where to start.

Overfilling the oil could have put excess oil/vapor through the PCV system. maybe a new valve and cleaning/replacing hoses. Also, maybe running the spray SeaFoam into the throttle body would be good ideas.

In general, I think you'd be right about the re-learn issue when experiencing rough-running after an ECU reset. But it could take several drive cycles. Not just waiting 30 minutes and turning it off/on again. maybe days And it probably means a sensor or system has drifetd quite far from 'ideal' and the system will have to make a lot of adjustments with the knock sensor and fuel trims, etc.

If it consistently is bad when cols, better when warm, after a few days of use, maybe the Engine Temp Sensor portion of the temp sensor is bad? I think in you car it may share the same housing as the coolant sender but not sure. Older soobs and 2 separate units with one dedicated to Engine Temp that the ecu used to determine if it was cold enough to 'choke' the engine with extra fuel.
 

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'01 2.5. auto.
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49 Posts
Discussion Starter · #7 ·
Thanks for the response Texan,

Good thinking with the pcv system.

About the re-learning; what exactly is a "drive-cycle"? I've seen and used that phrase, but is it just one period of time from start-up to shut-down?

I'm hoping it just solves the problem itself, before i start dumping money into it, i'll keep this thread updated.
 

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19,395 Posts
There are several different types of "drive cycle" involving different combinations and times, but essentially they begin with a cold engine, start engine, idle, drive at different speeds, including stop-and-start and some highway, with engine at "normal" temperature, then idle, and shut down.

the oil was running low so i topped it off and accidentally overfilled it.
"overfilled" -- by how much? Was any spilled on the engine?
 

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'01 2.5. auto.
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49 Posts
Discussion Starter · #10 ·
UPDATE:

so for today and yesterday it stopped improving 15miles down the road and the CEL stays on and it runs terribly; no power, sputtering and stalling when stopped, runs very rich. I need it by Sunday, so I think i'm going to get it diagnosed at the dealer, then put the parts in myself. I just don't have the time to throw parts at it and hope it works.
 

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Do you have a code reader? At least that would give you an idea of where the problem might be, even if you take it to the dealer.

If the codes are still misfires in cylinders 1 and 2, I would note that those two cylinders are paired in the coil -- if the coil is failing on that circuit, it can affect both cylinders. Also, if there's a problem with the spark plug wiring to either cylinder, or even a problem with one of the two plugs, it can affect the operation of both. I'd at least revisit the wiring to the two cylinders and their plugs. Look for a plug wire that might have pulled out. Perhaps, at night, apply a very(!) fine water spray in the area of the coil, and the plug wires and watch for sparks and lightning-type displays indicating leakage.

The half qt oil overfill doesn't seem like much - not the best but I tend to doubt it had anything to do with the current symptoms, if that's all it was. Perhaps just coincidence.
 

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'01 2.5. auto.
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49 Posts
Discussion Starter · #12 ·
Do you have a code reader? At least that would give you an idea of where the problem might be, even if you take it to the dealer.

If the codes are still misfires in cylinders 1 and 2, I would note that those two cylinders are paired in the coil -- if the coil is failing on that circuit, it can affect both cylinders. Also, if there's a problem with the spark plug wiring to either cylinder, or even a problem with one of the two plugs, it can affect the operation of both. I'd at least revisit the wiring to the two cylinders and their plugs. Look for a plug wire that might have pulled out. Perhaps, at night, apply a very(!) fine water spray in the area of the coil, and the plug wires and watch for sparks and lightning-type displays indicating leakage.

The half qt oil overfill doesn't seem like much - not the best but I tend to doubt it had anything to do with the current symptoms, if that's all it was. Perhaps just coincidence.
I took it to autozone to have the codes read yesterday, nothing has changed, so it's probably still the same codes. I checked cyl 1&2 wires and the brass terminals on the coil, it all looked good. The plugs are wires are only 25k miles old.

I just don't want to drop 80 bucks for a coil and then it not be the problem. Also, because I need to drive the car 400 miles sunday morning, i think i'll just get it diagnosed at the dealer tomorrow morning and then fix what they say before then.
 

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i'll just get it diagnosed at the dealer tomorrow morning and then fix what they say before then.
Hopefully, the dealer will identify what needs to be done, and let you take it from there. Most will charge for code reader level diagnosis, let alone identifying exactly what needs to be replaced, especially if the work isn't done by them, and there's no certainty that a code will narrow it down enough in any event. That's why knowing what the codes are gives you a bit of step up.

Your 01 has an integrated coil/igniter. More like $150 new, from on-line Subaru sources -- probably more at a dealer counter, less if used.

Please let us know how it works out, and have a safe, untroubled trip.
 

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'01 2.5. auto.
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Discussion Starter · #14 ·
Hopefully, the dealer will identify what needs to be done, and let you take it from there. Most will charge for code reader level diagnosis, let alone identifying exactly what needs to be replaced, especially if the work isn't done by them, and there's no certainty that a code will narrow it down enough in any event. That's why knowing what the codes are gives you a bit of step up.

Your 01 has an integrated coil/igniter. More like $150 new, from on-line Subaru sources -- probably more at a dealer counter, less if used.

Please let us know how it works out, and have a safe, untroubled trip.
Do the outbacks have any problems with coils from parts stores like autozone? I know the plug wires need to be OEM, but I haven't read anything about the coils.

I will definitely keep the thread updated over the next couple of days. Thanks for the kind words. :7:
 

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Do the outbacks have any problems with coils from parts stores like autozone?
Don't recall hearing about problems with the coils, but there have been posts about problems with alternators and starters. The current Autozone website listing for their Duralast brand of coil for the 2001 2.5 has the price at $129.99, and looks as if it's "special order". (Ignition Coil | AutoZone.com).

But this all depends on what the dealer's diagnosis shows . . . .
 

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'01 2.5. auto.
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Discussion Starter · #16 ·
UPDATE:

The dealer diagnosed the coil as being bad. I decided to spend 180 on the OEM one. They also said when the coil went, because of all the gasoline going into the exhaust it blew out the cat converter. I took it home and swapped coils and it runs perfect. The CEL is still on for the cat, but i'll deal with that after my move this weekend.

How have you guys replaced cats before? Do you need the subaru ones or can i get one off rockauto?

Thanks for all your help everyone.
 

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Did you clear the codes after replacing the coil?

If not, there might not be any problem being detected. In other words, the P0420 might have been due to the misfires, and once the coil was replaced and the engine was running properly, there might not be a problem. However, the CEL won't immediately clear. It will go out automatically only after three full consecutive driving cycles without any problems being detected.

A better approach would be to clear the codes after replacing the coil, and then see if the CEL comes on again. If it does, then the codes are re-read to see exactly what is triggering it.

A P0420 is often misinterpreted to be the cat when it could be something else, including a/f and O2 sensors. If the P0420 code reappears, and if you haven't already done so, search here for P0420 -- lots of posts . . . .
 

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'01 2.5. auto.
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Discussion Starter · #19 ·
that's a good point plainOM, i don't have an OBDII scanner to clear it myself, but I think a buddy of mine does, or i'll stop in at Autozone.
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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Hello All,

Just got on the forum. 99 Outback went 300k miles before getting totaled. 01 VDC just flipped 175k and am going to SC it in the next month.

I would like to clear up a few misconceptions if I may:

Resetting the module by disconnecting the battery or using a scanner does not do anything but clear the computer memory of any DTC's and resets the emission monitors. There is no "relearn", only the necessity for the vehicle to be driven to reset the emission monitor programming. These monitors set once the system sees the appropriate feedback from the sensors doing the monitoring. All cars have the same programming in OBD2. The drive cycle varies by year, but unless you are concerned about an emission test in your state, you need not worry about the monitor reset procedure. EVAP, Cat, O2 heater circuit, O2 sensor and EGR are the common monitors that require a drive cycle. The EVAP always takes 2 cycles to set. Subarus generally set all monitor within 12-25 miles of the cycle run unless there is a problem.

If a problem is detected outside the range of the emission monitors, the MIL will come on regardless of the monitor status. Any issue within a monitor system will only illuminate the MIL after the monitor is set. Example, if there is a problem with the catalytic efficiency, the MIL will not illuminate unless the Catalyst monitor is complete. You won't know if its complete without a scanner.

Just because a code states "Catalyst Efficiency Below Threashold" (P0420), does not mean the converter is bad. The rear O2 sensor sends info to the PCM concerning the amount of unburned fuel exiting the CAT. When the comp gets a steady rich state from the rear sensor, it knows the CAT isn't functioning as designed, but doesn't know why. If the rear O2 sensor mirrors the front O2, its a dead give away that the CAT has failed. Misfires, thermostat failure, bad grounds, faulty sensor, cheap gasoline; these all effect the ability of the CAT to reburn the exhaust gases. Too much unburned fuel, misfires, will damage it over a long period. Cheap gas will do the same since it won't burn efficiently in combustion.
 
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