Weird AFR and fuel trims P1170 P0171
 

Recently been having an issue with my fuel trims. They will usually be okay cruising but under load or on off throttle they will climb gradually up to the point I threw a P1170 P0171 with a gas smell in car. Also noticed when on off throttle while driving my AFR well briefly jump around from 13-15. It's almost like it's always hunting for the right ratio. Please help this is driving me nuts.

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Any recent work done? I'd look jnto airflow meter or a/f sensor first. If your scanner can see those PIDs, check against specifications. Make sure all intake piping is secure, no vac lines disconnected.

No recent work done I flashed back to the stock tune on my OFT about a week ago which didn't help. I checked all the lines and everything seems okay. the only real thing it might be is I guess the sensors, how do I check if those are okay?

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Any other mods, like a header? I would start looking for vacuum leaks and/or exhaust leaks particularly in the exhaust manifold area. I had p0171's due to a vacuum leak, the ECU interpreted it as being too lean and kept dumping more fuel in causing the raw fuel smell.

Just a cat back and the Perrin inlet tube with stock air box, which I have been running in conjunction with OFT tune for 50k+ miles with no issues. I'll check again tomorrow afternoon its such an odd thing that's happening. It seems too run fine under steady throttle then start to dump full when I'm off then back on throttle, which is when I see it hunt for AFR and fuel trims start to rise. Car has 98k miles now. Haven't swapped o2 sensors yet.

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Most of the reference specs that I have access to involve the use of an oscilloscope. If you have one, I can get you some useful info. Otherwise, you'll have to search out info.

I also looked up the P0171 for a 2013, and it indicated that a thorough inspection of your intake plumbing is warranted. Wherever the intake tubing has those bendy bits you'll want to look to make sure there are no breaks. If the intake tubing is cracking, you could get intermittent unmetered air going into your engine. (Like in the case of on/off throttle where the engine is torqueing/moving slightly) If this is happening, you may get those erratic fuel trim readings, as well as a lean code.

Go over those hoses really well with a bright flashlight looking for cracks/tears wherever it flexes.

Okay so I'm pretty sure it's one of my injectors left side. The thing is absolutely filthy and don't think it's running properly.

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Make sure the injector connector lock tab isn't broken. I've seen that before. Also happens on coils. Be careful removing. Replacement connectors are cheap if you find one broken.

Keep us posted :)

Edit: (If lock tab was broke you'd probably have misfires too, which you didn't mention so that's less likely.

You might be onto something with the injector, but you may wanna smoke test the intake connections first just to be 100% sure. If you're smelling fuel in the car that's the ecu trying to compensate for not getting enough fuel, therefore dumping a ton of it from the working injectors.

Remember, if you plan to replace then you should replace all 4. One brand new plus three with 98k miles doesn't make any sense.

Alright so got the injector on the way found a used one from a wrecked car here, also ordered spark plugs cause why not, they need to be replaced anyway. I did buy new clips and o rings, just in case should arrive this weekend and I'm gonna try to put them on next week after I get them tested just to make sure they are all running right. Thanks for the help guys, this should solve the issues but I'll let you all know how it goes good or bad.

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So got the spark plugs changed 6 hours later...I was exhausted didn't change anything, new injector didn't help so dropped it off at a reputable Subaru mechanic today he said it was bad bank 1 sensor which is I believe the afr sensor which comes in Monday. Hopefully this is it, I'll keep y'all updated next week.

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Oh and he also mentioned it could be something blocking the cat. Has anyone had one go bad yet?

Figured if it is it's a good excuse to get a new header [emoji848]

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There was a buddy of mine who had tons of issues with his car, fuel and air related most of the time. After months of debugging, it turned out to be a clogged cat. He was running catless header but the front-pipe cat just destroyed itself and blocked most of the way. Very much worth a shot for you to inspect that, front-pipe isnt hard or long to remove.

Also worth mentioning when I changed the spark plugs their was some oil inside and on the little electrical connectors for the coil packs. None on the spark plugs or inside the ignition coil itself. Should I give those a good cleaning with electrical cleaner?

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Could this actually be there source of my problem?

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Oil on the spark plug threads? No, that isn't a big concern. If you see carbon tracking on the plug ceramic or frank oil on the coils, I'd start to worry. Regardless, I wouldn't necessarily suspect a lean condition from that.

High trims on low throttle while moving (semi-engine braking) is indicative of a vacuum leak, particularly if the trims are closer to normal on throttle. Have you checked the PCV and EGR systems? Using your OFT, I would check the "Boost" value at idle and I would check the MAF voltage on and off throttle. If those seem out, it might help point you in the right direction. Worst case scenario, I'd do the following:

1) Pull the MAF and clean it with an isopropyl alcohol-based cleaner, let dry completely
2) Pull the PCV valve and clean/replace it (they're stupid cheap and kind of a pain to clean). Check the hose from the PCV valve assembly to the intake manifold for damage.
3) Check the EGR return tube into the intake for damage. Trace it back to the engine and determine if it's loose (it's hard to see without pulling the manifold).

If nothing changes with all of that, find a friend with a smoke machine and go to town. Personally, I have found that the exhaust manifold gaskets are susceptible to serious corrosion in the cold north where I live. I just finished tracing my own issues with high trims and it led me to completely corroded manifold gaskets which didn't even sound like they were leaking. Replaced those and my trims improved by >10%.

Edit: After reading the past posts more carefully, I see you said there was oil on the outside of the electrical connectors to the coil packs? That sounds like you have an oil leak, possibly coming off of the timing cover at the head or one of the camshaft sensor plates. There is a TSB for this. I have this same issue - my oil leak is not terrible and I think it's coming from the timing cover (instead of just the cam cover bolt/s), making this job an enormous pain. I'm waiting until I see oil on the ground to mess with it.

Alright so o2 sensor fixed it. Pheww thanks for all the help everyone! That was an epic stressful one. If anyone lives in KC I highly recommend kc auto worx. They helped a lot. Sometimes it's just the little things and FYI OFT sometimes will not show all codes thrown.

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Thanks for the epic write-up man. But it was just some electrical greese that had gotten a little darker overtime on the connectors. And anyone that has this problem such as mine should definitely check o2 sensor first in the future. But I guess this problem kinda forced me to finally do the spark plugs lol[emoji2957]

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No problem! Glad you got your issue figured out and fixed!

Out of curiosity, which O2 sensor died? I ask because awhile after I got my OFT and replaced my header with the OFH (catless), my secondary O2 sensor fouled and started trending my trims positive. I have always suspected the lack of the primary cat was the culprit; however, I have no way of really knowing. If your secondary died, since you don't have a header but have been running OFT maps, that would be really interesting as it might suggest something about the maps is accelerating the demise of the narrowband sensors. Then again, I've been running my new secondary O2 sensor for over 50k miles without any issues, and without a front cat, so maybe there was a bad batch at the factory...

It's definitely possible the more aggressive tunes will do this. And it was the front AFR sensor that failed bank 1. And I'm sure tunes don't help cats either. So I'll definitely be keeping an eye on them.

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