I installed new O2 sensors on the upstream side of my 2000 f150 xl 4.2l v6. Running the oscilloscope part of the torque app shows bank 1 sensor 2 and bank 2 sensors 1 and two running fine but bank 1 sensor 1 almost flatlined, having tiny bumps at the right time but barely coming off the zero. Nothing changed when I swapped the O2 sensors across. Ideas? It is dumping too much fuel and running in full lean condition. I have replaced all 6 injectors but not the fuel filter, doing the filter tomorrow. Also misfiring cyl 1.
Anything running through the OBDII port will not be fast enough to be a real oscilloscope.
Look at fuel trims at idle.
Now blip the throttle, do they go down closer to 0%?
If so you likely have an intake air leak.
In reply to underpowered:
Thanks, currently trying to chase that down. Hoping to find it's bad plug or wire but seller(bought in october) said both were new as well as distributor bloc. fuel filter helped it run smoother but it still has misfire and lean condition. Next Im going to test the fuel injector and possibly swap it to see if that changes the cylinder issue.
In reply to flatlander937:
Thanks. I'll check that tomorrow.
The O2 sensor signals only change as a result of ECU constantly changing the injector pulsewidth to lean/rich around stoichiometric perfect mixture.
Think of the O2 sensor as a thermometer, the ECU as the thermostat, and the temperature as the variable being controlled.
The fuel trims went to zero when I blipped the throttle from idle. Repeatedly. When I replaced the fuel injectors going off what the seller told me both intake gaskets were new and the upper looked new when I removed the intake. Should I just bite the bullet and buy and replace both gaskets?
Are both banks lean?
If so try unplugging the MAF sensor and see if it clears up and fuel trims start going in the opposite directions.
Your LTFTs might be +20 still, but if the STFT goes to -17 or so its trying to make a correction. This would indicate a bad MAF sensor.
If this doesn't happen then I would pursue looking for intake leaks. Look at the rubber intake boot for holes in the bellows before you replace intake gaskets.
Edit: also just FYI any time you check fuel trims, make sure its running at operating temp(or use scan tool to make sure its running in CLOSED loop, not OPEN loop).
B1S1 is stuck low, at zero volts, correct? If you unplug the sensor, does it go to a flatline at .5V? That would tell you the circuit is ok, and you say you have switched the sensors side to side with the problem remaining. If all the above is true, the sensor is reading correctly, and you have a mechanical or electronic running issue.
In reply to flatlander937:
Always at operating temp when testing. Unplugging the MAF sensor raised the LTFTs to 8.59 but the STFTs stayed the same going down to a low of -3.19 or so. Thinking the MAF is ok.
However,
In reply to Streetwiseguy:
B1S1 I unplugged the sensor and it stayed at zero volts. So thats a problem. I wouldn't have a clue where to start looking beyond poking my multimeter at it. Any insight on where to put the leads?
In reply to gunner:
Unplug B2S1 and see what it reads. Most of the time the scanner will sit at .5V when the o2 is unplugged. If it (B2S1) does do that, B1S1 could have either a grounded signal wire in the harness, or the ECU has E36 M3 the bed. If you can backprobe with a voltmeter at the ECU, check voltage on the signal wire there, then either pull that wire out of the connector, or cut it in a location that you can repair it easily after. Cut wire, scanner signal goes up to .5, you have a harness problem. Stays at 0, ECU problem.
gunner wrote:
In reply to flatlander937:
Always at operating temp when testing. Unplugging the MAF sensor raised the LTFTs to 8.59 but the STFTs stayed the same going down to a low of -3.19 or so. Thinking the MAF is ok.
However,
In reply to Streetwiseguy:
B1S1 I unplugged the sensor and it stayed at zero volts. So thats a problem. I wouldn't have a clue where to start looking beyond poking my multimeter at it. Any insight on where to put the leads?
Wait a minute.
What are your fuel trims(long term and short term for each bank) to begin with?
Because a -3 and +8 are perfectly acceptable. In time the long term will correct itself. Up to about 10% is generally OK.
Are there actual codes being thrown?
Edit: figure out the O2 voltage issue first as per streetwiseguy. Unplug bank 2 sensor to see what it reads on the scanner for reference what disconnected.
In reply to flatlander937:
I just got back to the computer and haven't looked at the truck since about 1. What I can recall is unplugging the MAF made the LTFT go up about 3 to 8.39? and the STFT go from .88 to -3.19. codes thrown are cyl 1 misfire and O2 sensor no signal running in lean condition bank 1.
Just to clarify that is b1s2 and b2s1 and b2s2. B1s1 is still 0v.
Unplug b2s1 and watch the scan tool. Does it also read 0v just like b1s1 when this is done? Or does it show something else?
Do as streetwiseguy said above if it doesn't show 0v on b2s1 when unplugged.
I unplugged b2s1 and it went to 0v just like b1s1. plugged it back in and same. So then I had 0v on both and 0 on fuel trims and short term %. So I started shaking down the wires back there in frustration to see if anything would shake loose. That's when both banks came up. only thing is bank one sensor one roves between 0v and .01v the others from 0v up to .88. all the trims reading between 13% to 23% or so and bouncing around happily.
wiring issue I guess. I cleared out the codes so I'm watching to see what comes back up.
Not a final note because I still haven't back probed the wiring for the o2 sensor but I did figure out one of the original issues which was a misfire on cyl 1. After swapping wires around from one and two to no avail I began to swap plugs between 1 and 2 and checked the gap. the first one was supposed to be .054. I already had the .054 slider out so I didn't check actual gap for those two plugs but they were less than half of that at my guess. Hey, the guy told me he put new plugs in it, why would I question if he had ACTUALLY GAPPED THEM? After setting the correct gap, the misfire magically disappeared. Wow. just wow. A week later I gapped the other four and they were anywhere from .030 to .044 so after fixing that up the truck started and ran better than it has since I bought it. It runs so good now I'm putting off fixing the intermittent o2 sensor till spring.
Finally fixed! A confession: I failed to mention last year that when I put in new fuel injectors I mangled one of the retainer clips clamping the injector to the rail. Being the smart guy that I am, I left injector 1, (yes bank one) without a clip. So last week I'm back on this problem and I remembered that I left it off, not realizing last year that a tiny issue like that would cause more air(hello lean condition) into the injector. After all I pushed it down really well. Sooo....I bought new injector retainers earlier this week and took it all apart again to install a clip on injector one, and guess what? A-la peanut butter sandwich, no more issue and no more check engine light. Say hello to stupid. (thats me!)
did that solve the dead o2 sensor issue?
It still bounces between 0 and .01 but since it nixed the check engine light and runs better (sounds like it should now) I'm going with it.
