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Rough running, shifting, and idling, weird o2 sensor graphs

6K views 40 replies 7 participants last post by  MSTWNTD 
#1 ·
I recently purchased a 2011 Honda Accord 2.4 from a family member for an extremely cheap price. It only has 20K miles, but it sat for months at a time and was only driven a few times a year. As a result, I have had multiple small, but still extremely annoying issues. I want to tackle this one before anything else. I have attached some screen grabs of live data. The car runs pretty rough. When it idles, there is a very noticeable vibration, acceleration feels lumpy, and the transmission shifts very roughly, presumably because the engine just faceplants every time it shifts. Some direction or things to check would be amazing. Thanks
Data while idling:
Screenshot-20201019-055510
Data while cruising at 40 mph around 1800 RPM:
Screenshot-20201020-110530
Screenshot-20201021-044552
 
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#2 ·
The AFR looks fine. You'll get more stable AFR if you get a new O2 sensor and clean the MAF sensor. I'd make sure to go through and change all the fluids on the car first. Do the 3x drain and fill on the transmission first, check all the mechanicals, a fresh tank of gas with water remover, etc.
 
#3 ·
Thanks! I flushed all the fluids as soon as I got the car, including the transmission 3x. I've put over 4k miles on it in the past 2 months and multiple fuel cleaners. Something is definitely wrong though. Sometimes it runs perfectly fine for a short period then the next drive cycle it slams through the gears and the whole car shakes at idle. I've seen up to - 14% fuel trims combined when that happens. I'm definitely willing to change the upstream sensor, I just wanted to see if there was anything that could be throwing off the data. Could a bad ground or wiring throw the data off? I've compared it to an almost identical car and the o2 sensor stayed steady at around 0.6v and it idled and drove way smoother than mine even though it had 140k miles
 
#4 ·
Good for you getting all that done already.
I'd replace the upstream O2 and see if that helps.
 
#5 ·
If the o2 sensor ends up curing it I will be genuinely perplexed. I have no idea how it could fail with such low mileage. One of the other issues I'm having is a light knocking at idle with no load, and the ac compressor squeaks every time it engages. I replaced both the serpentine belt and the tensioner because the tensioner failed and was knocking extremely loudly. I used a continental belt and an oem tensioner.
 
#6 ·
Apparently O2 sensor can just fail out of nowhere (so I was told). Is the knock an actual engine knock or just a knocking sound?
 
#7 ·
It's coming from the passenger side. I don't think it's from the engine, maybe from something on the belt drive? I don't think it could be anything in the engine itself. I'm running amsoil signature series so it's definitely not an oil problem.

It's very faint and intermittent but it's definitely noticeable from inside the cabin. It's harder to hear from the engine bay surprisingly
 
#16 ·
Here are a few clips. It's hard to hear, especially in the video. Things I could pick up were the fuel injectors ticking (pretty normal, just sometimes louder than others), the very faint knocking, the squeak when the a/c kicks on, the bogging down of the engine when the a/c kicks on, and the power steering whine (not sure if it's normal)
 
#9 ·
I assume there are no codes and no pending codes? I have to assume the bad running and idling is misfires. I do not know if you have a tool to look at the misfire counts.

Lacking that information, I would pull the spark plugs and examine those to see if there are any clues. I suspect a bad fuel injector, but the misfires would at least narrow it down. It could be a sticking EGR or blocked runners as well. That might explain the pinging.

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#10 ·
I assume there are no codes and no pending codes? I have to assume the bad running and idling is misfires. I do not know if you have a tool to look at the misfire counts.

Lacking that information, I would pull the spark plugs and examine those to see if there are any clues. I suspect a bad fuel injector, but the misfires would at least narrow it down. It could be a sticking EGR or blocked runners as well. That might explain the pinging.

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No active or pending codes. I don't have access to misfire data unfortunately. I replaced the sparkplug with the ngk ruthenium variety after driving it 1k miles myself and they all looked even. I thought they might look a touch on the whiter side, but they even is what matters most. WOT pulls feel plenty powerful for what it is but the transmission still shifts rough from 1st to 2nd. Could there be a problem with the evap system? I'm just frustrated that a car this new runs this bad and I have no codes to offer me any direction. Would there be any benefit to pulling the fuel rail and seeing injector spray pattern and possibly external cleaning?

I assume there are no codes and no pending codes? I have to assume the bad running and idling is misfires. I do not know if you have a tool to look at the misfire counts.

Lacking that information, I would pull the spark plugs and examine those to see if there are any clues. I suspect a bad fuel injector, but the misfires would at least narrow it down. It could be a sticking EGR or blocked runners as well. That might explain the pinging.

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It's never really run 100% good, but the fuel trims fluctuate. Sometimes the ltft and stft combined are around - 14% with the stft never settling around 0. The car runs the worst at that point with very rough and abrupt shifting and rough idle, with the engine bogging down around 200 rpm when the ac kicks in. Sometimes it runs better with the fuel trims at 0% combined. The weird thing is that the o2 sensor graphs never change. At idle, they steadily fall, fluctuate a few times in the middle, and then spoke back up to 0.8v. I've never seen anything like it. I'd like to figure out the squeak/very faint knocking noise coming from the belt drive but that's secondary to this. The car is just annoying to drive and I don't want to cause any damage by ignoring it.
 
#11 ·
Just out of curiosity, does the "extremely cheap" price for the car justify the hassle of doing all of this work? Sounds like the sitting has caused an awful lot of issues. As much as I love Accords, they're pretty regular cars, not classics or anything.
 
#14 ·
Thank you!

Take a video if possible.
The video is uploading now and I'll post it as soon as it's done. The weirdest thing is that you can't hear the squeak from when the ac kicks in from the engine bay, only the interior. Also, I've noticed that the ticking is louder when the fuel trims are poor. I wonder if the injectors are what are making noise since the engine is under increased load from not running correctly.
 
#15 ·
Just for grins check the air tube from the throttle body to the airbox and make sure that it has no leaks.

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#21 · (Edited)
It is running extremely rich, can you guys not see that?? That's why the negative fuel compensation. Hondas run naturally lean and you should see normally between 0 to 8% STFT and LTFT. I almost never see negative fuel trim numbers, only when I let off throttle I see a brief second of negative short term fuel trim.

Reasons of rich running can be:
  • exhaust leak
  • defective O2 sensor -> this one is unlikely but you can test resistance of the O2 sensor.. I did not change the bank 2 O2 sensors in my 07 V6 until 300k miles. It smoothes out the STFT curve. But again, I had never seen negative fuel trim on either old or new O2 sensors.
  • defective MAF sensor
  • leaky fuel injectors -> you would have to pull the fuel rail out to identify this

The 1st free thing to do is to try disconnecting the MAF sensor and read the STFT at idle. EGR issue actually causes very high positive fuel trims, same for any type of vacuum leak such as cracked intake hose.

The latter part of your video sounds like a loose timing chain inside the chain case. I suggest you open up the timing chain tensioner cover and inspect tension.
 
#22 ·
What a post! Thank you! I'm currently out of town, but I will work my way through this list as soon as I get back. I've heard of the VTC Actuator issues on these engines. Could that possibly be the source of the knocking? Here's my main issue with this car: how could a car with this few miles have issues like this? It's not like it sat for multiple years without being started. Normally I would start with things most likely to fail due to high mileage or neglected maintenance, but those don't really apply here
 
#24 ·
It's from my 93 y/o 2x great aunt who has dementia. I talked to her but she doesn't remember much and she got rid of all of the service history. All she remembers is that she did the oil changes when the service minder came on. The car was garage kept but it lived in PA so it had its fare share of cold conditions.
 
#26 ·
Another update: I unplugged the MAF sensor again and the a/f ratios were still sloppy. The o2 sensor has the exact same pattern as when it's plugged in. My main suspect is the o2 sensor since it doesn't seem to change or respond, regardless of the fuel trims. lmk if you have any objections to that

 
#27 ·
You now can test the resistance of the O2 sensors. I do not have the service manual for 8th gen, but you can identify bad O2 sensors by testing resistance of certain leads, you just need to unplug it and take a multimeter to it.
 
#28 ·
I got impatient and just replaced the upstream sensor with the oem part just now. The throttle response is much smoother and the shifts smoothed out a lot, but the o2 keeps jumping from reading full rich to full lean. I'm honestly clueless as to what could be causing this.
 
#35 · (Edited)
What is the long term fuel trim now?

The trim is going to bounce all over the place according to driving conditions but your long term needs to be between 0 to 8 ~ 10%+

And did you look at your catalytic converter while you had sensor 1 up out? Does the honeycomb look ok? There was another dude here that was doing all sorts of mods and had weird bucking/lurching issue, turned out his RV6 high flow cats were melted.
 
#40 ·
Update! I just cleaned my fuel injectors and replaced the seals with no major improvement; however, when I was cranking the engine to release fuel pressure in the system, my engine sounded like this: I have watched a few YouTube videos on performing rudimentary relative compression tests like this, and it sounds to me like I have 1 cylinder with low compression. I am trying to get my hands on a compression gauge to verify this. What would be the first places to look for lost compression if this proves to be the case?
 
#41 ·
UPDATE: I took it to an independent shop to get it diagnosed. It took them about a week to figure it out, but they diagnosed it with a bad Intake Camshaft Position Sensor and a Coolant Temperature Sensor (the one on the water pump) that was stuck at 40 degrees. I replaced both sensors with OEM parts and the engine response is perfection now. They told me not to worry about the uneven cranking and they see nothing wrong with the O2 sensor graphs. The only issue I'm left with is VERY rough shifting. Every downshift and the majority of upshifts are harsh and make my head bob forwards. It's incredibly annoying and it can't be good for the transmission. Any suggestions about this, or should I make a separate post? I've heard that Hondas don't have the best shifting algorithms but I've been in Accords with over 100k miles that shift infinitely smoother than this
 
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