2008 OB 3.0, Sudden onset of bad misfires

[Hocrest]

My 200k mile outback has been running great, then yesterday while sitting at a red light, it started misfiring and stumbling. Codes are just the various misfire codes for cyl 1-6. It seemed to be mostly cyl 1 but I think all have thrown a code at some point. Running with the RPMs at cruising (2-3k) it's not to stumbly but will still throw codes. 

For the next week I'm traveling for work between hotels and airports, and a few hours away from home, so work/diagnosing is limited. I have my my OBD plug and Torque so I have basic access to lookup.

What are some things I should look at.

[forester2002s]

Recently filled-up with (bad) gas?

[Hocrest]

1 hour ago, forester2002s said:

Recently filled-up with (bad) gas?

I filled with about 13 gallons the day before, and put about 70-80 miles on that tank before it started acting up. I'm down below half a tank now.

Edited August 13 by Hocrest

[el_freddo]

Coolant level still good?

I’m thinking with that sort of mileage you could have the beginnings of a dead head gasket, leaking valves or dying coil packs. 

I don’t have any real world experience with the H6, I’m just going by what I’ve read from other ppl’s and a mate’s experience. 

Cheers 

Bennie

[Hocrest]

S

4 hours ago, el_freddo said:

Coolant level still good?

I’m thinking with that sort of mileage you could have the beginnings of a dead head gasket, leaking valves or dying coil packs. 

I don’t have any real world experience with the H6, I’m just going by what I’ve read from other ppl’s and a mate’s experience. 

Cheers 

Bennie

Sorry I wasn't clear.

I drove for about 80-100 miles since it started misfiring so the mileage is on par. During the 2 hour drive running like crap, the temp stayed normal.

It's been stuck in a valet lot since I got to this work conference. I'll be getting access to it when I'm done today and plan to look at the fuel and fuel filter.

[brus brother]

My 2008 ran like crap after high humidity/cool conditions. Was ready to change out coil pack and instead dried out the interior contacts of the pack where the wires plug in and sprayed with WD40 and all was well.
Have you tried spraying water around the wires when dark outside with car running to see if there are any sparkly light shows? In my case, I didn't have the light show but the rough running was related to the damp coil pack.

Fingers crossed for something simple.

[idosubaru]

Hey dave. Vacuum leak, air flow sensor, or solder joints in the ECU injector board are bad.

Replace the air filter recently?  Make sure the box and clamps are all seated properly and tight.

Not sure how to test mass air flow sensor. I have a 2006 3.0 Tribeca which is a nearly identical engine. If it’s the same I could mail you to test so it’s there where you’re done traveling, although I’d need it back eventually as it’s on a drivable vehicle.

Bake the board only no plastic and don’t let it touch any metal in the oven for 6 minutes at 375 with your chocolate chip cookies to reflow the solder.

But to be clear on diagnosis:

You were getting codes for all 6 cylinders?  Like all at once?  One time?  Or they were intermittent and random?

There were no other codes present?

 

 

[Hocrest]

I didn't replace the filter but I had it opened up a few weeks ago, I'll check all of that. 

On the dx, no other codes. The misfires are randomly across all 6, but not all at once. After running it long enough they're pretty much all there though. Definitely both sides. 

I'm down to about 5 gallons, I want to burn up another 2 then fill. That way if it was bad gas I'm not mixing to much of the bag with good. It's currently parked at the airport until Sunday night when I get back to it to drive home.

[Hocrest]

So last night I finally got the '08 back home after a 4 hour drive. Luckily I didn't get to the car from the airport until after midnight. So, for the first time since the issue started I wasn't in a "high traffic" area where I didn't know where I was going.

• I was able to pay a little more attention to when it was acting up and what Torque was showing.
• I unplugged/replugged the MAF and checked all of those pipes.
• The road at the beginning was wet enough to create a "spay" and that didn't seem to make things worse.
• Filling it with fresh gas didn't seem to do anything.
• I noticed that I could reliably get codes for 1 and 4 misfires. If I let it run rough for a while, I could get codes for all 6.
• If I could keep it around 3K rpm it ran fine. And it would even self clear the CEL if I kept it in that range long enough. For most of the trip, I used the "Manual" shifting to run it between 3-3.5k. 

I didn't get home until close to 5am and had to be at work for 8am so I haven't looked at anything else. The way that it was consistently coding 1 and 4 makes me think the coils are bad. I did order a 6 pack of coils and Amazon will have them here tomorrow. When I replaced the plugs a few months back, I replaced the boots, but not the packs. If it's not raining tonight after work, I'll probably try to drain some gas to see if there is any water, but I think a fuel issue would be giving more random cyl numbers.