Rough Idle 2, The Bad O2 sensor strikes back.

[rs2k]

My Explorer's idle started running rough again after a trip to a nearby town while towing. I put Torque Pro on and noticed both O2 sensors looked OK except for a few irregularities.

Irregularity 1: Bank 1 Sensor 1 (B1S1) was moving rich to lean a tad bit slower than Bank 2 Sensor 1 (B2S1).

Irregularity 2: B1S1's max voltage was about .1 volts less than B2S1 and the min voltage was about .1 volt higher.

Irregularity 3: B1S1 took much longer to heat up than B2S1.

Irregularity 4: Long Term Fuel Trim (LTFT) on bank 1 was near 0% at idle while it was near +16% on bank 2.

Irregularity 5: Getting misfires when the engine is cold.


History: When I had my exhaust rewelded 6 months ago to fix a leak, I had the welder replace to two precat sensors. Turns out the welder accidentally replaced B1S1 and Bank 1 Sensor 2 instead of B1S1 and B2S1. I found out the welder got the sensors wrong when B2S1 went dead a couple of weeks ago.

Anyway, I made the mistake of buying cheapies from RockAuto. So today I went ahead and bought another high dollar Bosch "Premium" O2 sensor from AutoZone. After a computer reset the LTFT on bank 1 went back up to around +15% and the idle is now smooth again.


Long story short, Cheap O2 sensor went bad, don't buy cheap O2 sensors.

 

[DjDom]

Reminds me of this..

http://www.explorerforum.com/forums/showthread.php?t=392566

 

[rs2k]

Haha, I can see in that thread where my B1S1 sensor is starting to act differently than B2S1.

I'm done buying cheap parts. At the time I bought the sensors I wasn't planning on keeping my truck as a DD for more than a year or so.