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comatosellama

02 OBS sputtering and misfiring, I've tried everything !

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EDIT: FIXED: OEM O2 sensor from subaru parts counter fixed the issue

 

My 02 OBS has started being really really weird. When taking off, if I don't keep the rpms over 2k the car lurches badly, and starts to misfire and pop, then will take off. The pop sound seems to only come from the drivers side cylinder bank. The misfire sounds like an old hit or miss engine. It kind of reminds me of when the vacuum advance on my brat was out. Flooring it always seems to smooth the car out.

Car will then rip up to 65 mph without an issue (faster than ever with the new coil pack), and then will start to experience the same issue. I floor it at 65 and the car doesn't rev, it makes noise like it's under stress but it doesn't start going. Then after around 3-5 seconds of flooring it the car feels like it "breaks free" and will zip up to 80, until the car starts to sputter or hesitate again.

New coil pack made it a little better, it runs better than it ever has between 2k and 4500rpm

New fuel filter also seemed to help, but I'm not sure if it actually did.

IACV thoroughly cleaned, definitely helped the low end out a little, but it still bucks at low speed.


Throttle body cleaned


Did some top end cleaner and threw some heet in the tank, not sure if that helped or not but I like to do i

Cats, O2 senors, wires, plugs, air filter, knock sensor all have under 20k on them.

Scanner wont tell me fuel flow rates and stuff so I can't check that right now

Anyone ever experienced this? I'm not sure where to go from here except for a compression or leakdown test. My cylinder #4 has always slapped when cold, I've been worried about losing compression for a while now.

 

Thanks, CL

Edited by comatosellama

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no codes thrown?

how old is the timing belt system parts?

double-check cam/crank timing immediately.

you might consider dropping the exhaust and looking for 'dropped' (shifted) valve guides.

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What engine?

Hook up a vacuum gauge to the intake. See if the popping is going into the intake, gauge shows sudden high pressure.

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11 hours ago, 1 Lucky Texan said:

no codes thrown?

how old is the timing belt system parts?

double-check cam/crank timing immediately.

you might consider dropping the exhaust and looking for 'dropped' (shifted) valve guides.

No codes, timing system is maybe 10k old, was working perfectly since last October. Will check the exhaust. 
 

Is a compression / leak down test a good idea?

I was going to drop it off at a shop tomorrow, I’m in the middle of classes so I don’t have more than an hour or two a week to work on this.


But I’m not too confident in a non Subaru specialty shop when giving them a car with no codes and no obvious issues 

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10 hours ago, Rampage said:

What engine?

Hook up a vacuum gauge to the intake. See if the popping is going into the intake, gauge shows sudden high pressure.

2.5 SOHC non turbo 

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easy to check if the plugs and plug wires are seated completely.

I once saw a post where the plugs weren't torqued properly, relying only on the feel of the washer.

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don't dismiss the timing out of hand.. Check it!

one tooth off on one pulley is all it takes

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On 11/13/2019 at 11:28 AM, brus brother said:

easy to check if the plugs and plug wires are seated completely.

I once saw a post where the plugs weren't torqued properly, relying only on the feel of the washer.

It's at the dealer now, sadly I have no time or place to really get into it while I'm at school. Will update with what the dealer says. I wish i could have taken it somewhere else but around here people religiously drive american cars so there isn't a subaru shop around here. ( if anyone knows a good shop near michigan state let me know!!!)

In the meantime this loaner 2019 Crosstrek is treating me well, I'll just never understand why they made is slower than my impreza.

Edited by comatosellama

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Dealer says nothing is wrong .........

They say they checked plugs and wires, did a compression test, and that the car suddenly drives fine. Hopefully it actually does work fine.
Going to ask if they did a vacuum test, they said I shouldn't have aftermarket ignition coil, wires and plugs. Plugs are NGK so I'm not so worried about those. I'm pretty sure it's gonna come back as soon as I roll out of the lot though

The ascent I had over the weekend was 10/10, pretty much self driving, so $150 for a 4 day rental on an ascent isn't too terrible.

Those things can move, they're much much better than a crosstrek ( I had a 2019 crosstrek for a day as well)

 

 

update: car threw cyl 2 and 4 misfire codes while they were pulling it up to send me on my way. No charge for diagnosis because the codes threw after we signed the $0 bill which I kinda feel bad about, so I had them replace coil pack, wires, and plugs for $475 installed. Results of compression test are 

cyl 1 200psi

cyl 2 195psi 

cyl 3 200psi

cyl 4 185psi
 

not a bad price for diagnosis, compression test, OEM parts and an Ascent rental car for 6 days. 
 

EDIT: removed a line

Edited by comatosellama
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Did it for 3 or 4 quarter-half tanks at different gas stations.

The issue started a little back in early September, then I picked up my 89 f350 and didn't drive the impreza until nov 3rd. Car pretty much immediately started acting this way, getting worse over time. I don't think the snow made it worse, it slid around just fine the first day or two of snow, now it's unusable until this is fixed.

 

Drives fine at 3k rpm, hopefully the dealer isn't just throwing parts at it

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The dealer didn't retrieve any codes?

coupla things that can be bad without throwing codes; knock sensor and engine temp sensor. Knock sensor can kill power by pulling the advance. Some folks report cheap ebay sensors working well.

temp sensor can cause hard starting if NOT reporting a cold engine when cold, or, flooding/'choking' if always reporting a cold engine even when warm.

 

does the car behave better immediately after a battery disconnect ecu 'reset'? If not, I'd expect you're looking for something kinda physical; vacuum leak, low fuel pressure, sticking valve, maybe intermittent ground somewhere,.....?

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While the dealer was pulling up car after failed diagnosis, the car threw misfire for cyl 2 and 4 codes. I never saw these codes. Dealer says replace coil pack, plugs and wires with OEM. ( All good brands, under 20k old, plugs were already OEM).

 

Picked up car after they replaced parts.Dealer says issue is fixed for the most part, just hesitates a little while going down the road.  Issue came back within 500ft out of the parking lot. (I knew this would happen). Dealer work order shows mileage in and mileage out at the same reading, so they didn't even test drive it after their $450 "fix" before telling me everythign was alright.

Service advisor takes my car for a test drive after I came back, and it did to him what I had brought it in for, after assuring me it was better.

On my receipt for the coil/plugs/wires Dealer states front 02 sensor reading wrong, causing bad fuel trim, and rear o2 reading 0v. Dealer states they will not check into this issue because of my UEL headers. I ask why they replaced the other stuff without testing it just because it wasn't OEM, when they had a test saying something else was wrong. Again, dealer states they will not check into this issue because of my UEL headers, won't even try to fix it unless I get OEM headers and axleback back on the car.

After a long discussion with the service advisor and his manager I got a full refund. I then walked to parts counter and bought OEM upstream O2 sensor, replaced it on the side of the street a block down the road, and everything is fixed.

Annoyingly the O2 sensor I took out was an identical bosch unit as what the counter guy gave me, but this one works for now at least.

 

 

Edited by comatosellama
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Thanks for posting the fix.

If your scanner could show live data you could have looked at the O2 sensors and known what to do.

I use the custom menu on mine and set it to show engine temp, rpm and both short term and long term fuel trim.

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no reason to take a 17 year-old car to the dealer. Heck, probably none of the techs have worked on anything older than a 2010 - certainly not many....

look for a soob-friendly independent mech.

good job getting a refund !

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