The smartest guy in the room is usually the one that takes nothing for granted and assumes that everybody else in the room possesses knowledge that he doesn’t.
Reminds me of one of my favorite sayings (I think it is some Eastern thing) - even though I obviously don’t live up to it well: “Tis better to keep one’s mouth shut and be thought a fool than to open one’s mouth and prove it.”
My Jamaican father-in-law likes to point out that we have one mouth and two ears, therefore we should do twice as much listening as talking.
I Installed a set of Denso Iridium Plugs. To my surprise the plugs that were removed were Denso on the right troublesome bank and NGK on the left. I went back and had the ODB make another diagnostic. Nothing appears to have changed.
| Location Of OX Sensor | Fuel Trim | Voltage |
| Left Front | 13.9% | 0.7 |
| Left Rear | 7.0% | 3.3 |
| Right Front | 1.6% | 0.78 |
| Right Rear | 0.0% |
0.70 |
I checked back with Toyota And they said it is a bit unusual to have two different brands of plugs installed at the Texas factory, but they have seen it before. THe heat ranges were identical for the plugs. Guess it was a shift change or the start of Deer Season.
Anybody know how to interpret any of these readings?
The higher fuel trim % could be compensating for a vacuum leak, but how only on one side?
Leaks can be found with an unlit propane torch. When you apply gas next to a leak the idle will change.
It would have been nice to know each of the plugs looked when you pulled the originals out. There may have been some clues to the trouble indicated by checking their condition. I think the first tech gave you a good start by showing you the difference in the two sides. I doubt you need to replace all the O2 sensors but it may help to replace the one on the right bank at least to see if that fixes things. I suppose you could swap the two front ones and see if that changes things. I would check the plug wires out using a scope to make sure they are working ok.
Cougar,
When I took out the plugs none of them showed any unusal discoloration. I numbered them as well. I can send a photo if that would help. Good call on swapping the Ox sensors. I will try that.
Geekeldr
I did a little studing about LTFT and STFT on the web and from what I understand now the concern is more with the left bank numbers. Good fuel trim numbers should be single digits and close to zero. Higher numbers mean more adjusting is taking place to compensate for things going on with the fuel to air ratio. Positive numbers means a lean fuel condition so more fuel is being added to the mixture and negative numbers means a rich fuel condition so less fuel is being added to the mixture.
If the front left side numbers are staying that high all the time it may mean there is a air leak after the airflow sensor on the left bank somewhere and the O2 sensor thinks it is a lean condition and is trying to compensate for it
If the numbers you show after the percentages are really voltages from the sensors then the left rear is showing a real high voltage. The maximum voltage should be .9 volts I believe. There may be a problem with that sensor.