2007 subaru forester rough idle need some help.

2007 forester, checked for codes had code p2096 post catalyst fuel trim too lean. So when I got the car someone had erased freeze frame data so none there to help. But what data I have looked at was when I have the car at idle found short term fuel trim at 1.6 long term goes at about 2.4, when I check my fuel injector pulse seems high at 3.34 ms. I see the rear 02 sensor is way off reads about. .055v with scan tool I raise injectors to 10% increase and voltage to rear 02 goes up to .850v so it seems to help but vehicle still idles poor and feels to be misfire no misfire counts. MAF reads 2.6 g/s trying to see what direction I should go towards now. I thought I had I fuel issue but now I'm a little stuck.

I was curious, can a tight valve cause issue with rough idle, 02 sensor reading low and noticed black sputtering from exhaust also has sulfur smell

2007 forester, checked for codes had code p2096 post catalyst fuel trim too lean. So when I got the car someone had erased freeze frame data so none there to help. But what data I have looked at was when I have the car at idle found short term fuel trim at 1.6 long term goes at about 2.4, when I check my fuel injector pulse seems high at 3.34 ms. I see the rear 02 sensor is way off reads about. .055v with scan tool I raise injectors to 10% increase and voltage to rear 02 goes up to .850v so it seems to help but vehicle still idles poor and feels to be misfire no misfire counts. MAF reads 2.6 g/s trying to see what direction I should go towards now. I thought I had I fuel issue but now I'm a little stuck.

Take this with a grain of salt, but with the combustion process, it would use some of that O2 and convert it to other gasses, so a set or multiple sets of leaking exhaust valves could in theory do this as it’s not completing the combustion process.

I’m currently working on a 2019 Subaru sti with a hunting idle that leads to a stall(no codes) that I found to have low compression in cylinder 2. Leak down showed about 80+% leak out of the exhaust valves, and currently the owner is trying to decide how far he wants the fix to go, as in heads off refresh or just sell it. But the exhaust valve lash on that hole are certainly too tight(common on subarus).

Now I should mention this car is fairly modified with larger injectors, turbo etc so my data would not be super useful to you, but I’m happy to help in anyway I can
thanks!
Rick

Also it does sound like fuel to me, but if you have access to a scope you can run a relative compression (how I found my low cylinder). See what fuel pressure is(damn Subaru for not supplying a port lol), do a injector pressure drop test to see if anything comes up. Not sure what tools you have access to, but if memory serves me right that car has the bronze looking fuel filter just above the pump, and they are prone to clog.

Hope this helps.

Thanks Rick I appreciate any help I can get I took the car over for another tech when I checked compression as well I see that cylinder 1 and 3 bank are lower 100 psi, cylinder 2 and 4 bank were about 160 psi. That's even more making me think I have a valve problem. It would be nice if my fuel trims did something different but they stay close to 0. I do notice though when I hook up my scan tool and increase % of fuel injection my 02 quickly goes to .850

I may be wrong but 2.6 g/s sounds a bit low which may account for under-fuelling[?]

Will your scan tool allow more than 10% added fuel? Or could you use some external fuel to see if you can get the rear sensor voltage above .9? I don’t know the exact conditions the code is thrown, but generally I would imagine the sensor should be able to output above a .9 with a rich mixture. If it’s not able to it could be a bad sensor, bad grounds or possible just bad fuel maybe? Again, don’t take anything I say for truth but sometimes it’s good just to bounce ideas off others to allow the mind to reset a bit

I thinks 2.6 is correct it should be as close to the liter size of the engine which I believe is a 2.5

Thanks I appreciate any help, yes if I go up to 20% which is the max it does get close to .90v now the front a/f sensor is reading 1.2 v I did swap 02 sensors with a known good one but still same results

As far as the fuel filter on this year it's in the tank. I did check fuel pressure was reading 50 psi. I did want to do an injector drop but my scan tool doesn't have that option

Generally when I see a post catalyst lean code and the car isn't actually running lean, I look for an exhaust leak.

If that's the case it usually won't make the car run bad.
You might have another issue with the rough idle.
Is there any misfire data for Subaru?

Weird you don't have freeze frame data available but there still is a code.
It would be nice to see under what conditions it set and what the trims and up stream sensors had to say.

Noah wrote: Generally when I see a post catalyst lean code and the car isn't actually running lean, I look for an exhaust leak.

If that's the case it usually won't make the car run bad.
You might have another issue with the rough idle.
Is there any misfire data for Subaru?

Weird you don't have freeze frame data available but there still is a code.
It would be nice to see under what conditions it set and what the trims and up stream sensors had to say.

I just merged your threads to keeps all the information in one place. It will make things easier for everyone to keep track of.

Yes misadjusted valves can cause idle problems. The uneven compression values possibly point to the need to inspect valve clearance.
I know, easier said than done, lol.

Noah wrote: Yes misadjusted valves can cause idle problems. The uneven compression values possibly point to the need to inspect valve clearance.
I know, easier said than done, lol.

Leak down test is easier

Since the compression is bank specific valve timing is another possibility.

You are correct as always sir