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Hm.. One thing about an O2 sensor, if there are ignition misfires, the sensor will indicate a lean condition, not rich, as one might think. They only measure the amount of O2 in the exhaust, not fuel.
Makes sense. According to what I've read, a voltage reading hovering around .00 actually does indicate a lean condition. Unless I'm reading the sensor wrong, my 02 is indicating super lean. I've been backprobing the sensor from the HO2S and Sig Return Line like shown below:
MFI: 4.9L E/F Series and Bronco
I'm going to try to take a video of the stumble this morning.
You can't really use any non loaded readings for diagnostics...at idle it will read ultra lean if you get a reading at all, because it is lean. Idle afr, when read by a wideband, is 18+:1. Even snapping or holding throttle is not reliable.
Ted makes a great point, and on the flip side of that....too big a spark will cause all the oxygen to burn out and be a lean condition (Lololol......).
You can't really use any non loaded readings for diagnostics...at idle it will read ultra lean if you get a reading at all, because it is lean. Idle afr, when read by a wideband, is 18+:1. Even snapping or holding throttle is not reliable.
Ted makes a great point, and on the flip side of that....too big a spark will cause all the oxygen to burn out and be a lean condition (Lololol......).
Is your missfire at idle only?
I think so. It's almost more of a stumble. I've attached 2 videos showing the "miss"/"stumble" from the inside. You can feel the vibration of the miss inside the cab. Cold start, goosed the throttle to enter cold driveaway mode. From the engine bay, it doesn't look like much.
I blocked off the EGR flow with a ball of foil (just for kicks).
The stumbling got better, but didn't cure the problem. It took a little longer for the Check engine light to come on but not by much.
Also checked the Air Pump (which is working) and the diverter valve works with vacuum manually applied. How can I find specs to check to see if the TAD solenoid is opening at the proper time? Don't think it's the problem anyway...
So I'm down to MAP sensor and Fuel Injectors. I can get a replacement MAP sensor for $40 (aftermarket) or spend that much in a new multimeter+vacuum gauge to test it. Is it worth doing prior to pulling the intake and checking injectors?
Or is there a test I can get a dealer to run that would rule out injectors?
Did you ever try to get your o2 readings under load?
No, not just yet. I'll try to do that tomorrow (got to buy some alligator clips and T-pins to extend the multimeter wiring, unless backprobing from the EEC would work?
So I pulled my codes again to see if there's been any change in what the computer is storing.
KOEO - 111
512
I had been thinking the 512 was because of disconnecting battery, but I'm starting to think it may be a real issue. I've been running the truck now for about 1 month without disconnecting the battery, every day to work back and forth and then some. I expected the 512 to have gone away by now.
Are there any good troubleshooting guides to resolve the 512 code?
ALL THREE capacitors in the ECM have leaked out and two were corroded to the point of not making contact. Reman one on the way from RockAuto, and should be here Friday.
There's no way that all three failed in one day, so I've probably been running sub-optimally for quite a while with No CEL.
I put the re-manufactured EEC in on Friday, and spent the weekend putting some miles on it. Runs smoother than when I bought it, no CEL. I'll run for some new codes later this week to see if the now-working KAM is picking up any real issues.
Additionally, it had been doing some hard shifts after getting warmed up, and now all those issues are gone. Thanks 89F2urd and all others that helped out chasing this gremlin.
