If this helps point to anything at all, the AFR on bank 2 will rhythmically drop to as low as 8 or 9 and then go all the way up to 23 and then drop back down then repeat. Time wise it does this in a consistent patterned loop. AFR will drop and then go up in a steady pattern. Almost like in synch with a camshaft spinning
Again, sounds like sticky injectors
I’m guessing he meant swapping the bank 1/2 upstream sensors side to side just to rule out a funky one. It’s the upstream that’s responsible for the A/F readings (unless there’s something about this engine that I don’t know - which is possible!)
And that.
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Yes then upstream O2 sensors control mixture. And they are the fancier wideband sensors. Based on my 2013 Mustang GT, they look like a PIA to get to! I think the OP has the ability to stream data from each sensor. That would allow him to compare the signals.
https://www.underhoodservice.com/troubleshooting-wideband-o2-sensors/
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So usually called A/F sensors, I think, and technically a bit different from a typical O2? I’m asking 'cause IDK.
I was thinking they might be easier to get to than the fuel injectors? But IDK that either. Anyway, I’d be inclined to do whichever is easier first…
Come think of it though, can’t you do a half-a**-ed injector balance test by unplugging one at a time and basically seeing which plug doesn’t change anything by a lot? (While recording A/F sensors and fuel trims and whatnot). It might not be so easy to get to the injector connectors though.
Both types are technically A/F sensors but regular O2 sensors don’t measure air fuel ratio accurately beyond 14.7. Widebands measure a wide range of air fuel ratios accuratly from 20 to 1 to 8 to 1. Much more accurate information for the ECU.
The injectors are right on top of the engine. The connectors are easy to get to… but, a subtle idle miss would be hard to diagnose dropping one injector at a time.
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Hey guys, here’s an update on what I’ve tried so far
-Replaced intake manifold gasket
-Swapped coil packs bank to bank no change in banks with bad AFR
-Swapped fuel injectors bank to bank no change in banks with bad AFR
-Checked spark plugs on bank 2. A bit of oil and dirt on threads but electrodes clean
I used my scanner and got the following o2 readings. The o2 readings on the scanner coincide with the trouble code of P0141 with Bank 1 sensor 2 malfunction because it’s reading 0. All other 3 o2 sensors have some reading to them but I’m not sure how to interpret them. If someone could shed some light that’d be helpful.
Screenshot of o2 readings below was taken during idle. Also attached picture of what the spark plugs on bank 2 looked like.
Another thing to note is that when I first start the car up (doesn’t matter hot or cold) the car will idle fine and AFR on bank 2 will be fine for about 30 seconds. Then after 30 seconds it will start fluctuating like crazy and the problem starts…
So just wanted to clarify, the remaining things to check for (in order) would be:
1.) header bolt tightness or exhaust leaks
2.) maybe replace the bank 1 downstream o2 sensor (one mechanic I spoke to thinks all the o2 sensors are connected to one another and one bad reading from one could throw the others off, is this true?)
3.) compression test and removing valve covers
I also wonder if the dented fuel line could be the culprit, which incidentally is on the drivers side/bank 2 (which I posted about in another thread)…the dent hasn’t gotten bigger or worse since it first happened but I was wondering if it could be affecting the car? I think likely not because the dent happened 2 months ago and the car never had this problem until a few days ago.
With the check engine light on and a failed oxygen sensor, is the fuel system in open loop?
The oxygen sensor should be replaced before starting any other diagnostic work.
Isn’t that what the P0141 was, B1S2 O2 sensor??
Swapping the down stream sensors to see if the code follows starting to make any more sense now?..
Make sure the header bolts are tight, header bolts in general are known to get loose, I have to tighten mine often, also the header collector flange to the pipe and or converter, and the O2’s are tight as well as no damage to the wires and or plugs…
I might be thinking that steady fuel trim on the bad code side isn’t good. The bank with fluctuations is maybe a sign that the sensor is working to adjust things. My memory about these things is spotty because I can’t remember which readings do exactly what. Someone may add clarity later.
The other thing I saw was wiring. When testing O2 sensors, you should move the wires around and see if it makes a difference in the readings.
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Chart the Bank 1 and 2 sensor ones as lambda rather than current or voltage. Most scanners have the choice of lambda, hopefully yours does, too. Lambda of 1.0 is the target, less than one is rich and more than 1 is lean. Use the chart function so you can see how bank 1 compares to bank 2 as you drive. Post that if you can.
They should read very similarly and change little as you drive down the road. If you accelerate it should drop below 1.0 for a moment or decelerate and see it shoot up to 1.2 and more. And it will read the same way if you run E85 or gasoline.
https://www.motortrend.com/how-to/1711-explained-the-difference-between-lambda-and-afr/
It sound like you are on the right track, but the problem-causer is hiding. Be sure to check the PCV system and that the brake booster holds vacuum. fyi, a similarly hard to resolve O2 sensor problem was discussed here a few months ago:
The fault detected is for an open circuit in the oxygen sensor heater, your link is for a lean fault.
Before swapping O2 sensors, diagnose the P0141 code. Disconnect the B1S2 connector and measure the resistance across the two pins connected to the white wires on the sensor. If it’s open or very high resistance, replace the sensor before anything else - as suggested by @Nevada_545
Here are the lambada readings for the upstream o2s when idle. Short term fuel trim on bank 2 reads 23.4 but within a second it can go to -23.4 and then back to positive 23.4.
Something to note is long term fuel trim in bank 1 is -19.5. Not sure what this tells us about o2 sensors but i’m surprised the car hasn’t thrown any lean or rich codes.
I will definitely be replacing the bank 1 sensor 2 o2 tomorrow
That says the ECU is reading Bank 1 as too rich and pulling fuel out.
What is the long term fuel trim on Bank 2?
Likely that LTFT on Bank 1 won’t throw a code until +/-25%
I am leaning towards a bad O2 sensor on the Bank 2 position 1 if there is no exhaust leak.
An exhaust leak would seem to explain the widely varying STFT on Bank 2. Excess air being puled in will throw off the O2 sensor readings.
The last pic you showed had the Bank 2 downstream sensor showing a rich condition but only for an instant in time. You really need to show us the charts.
I fixed it! I replaced the bank 2 upstream o2 sensor and that got rid of the problem
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Good for you for getting to the bottom of that pesky o2 sensor problem. Suggest to mark your post above as the “solution”, then it will show up as solved and the solution will appear at the beginning of this thread, in the first post. This is helpful to others who are researching similar symptoms on their cars.
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