Tracking down a problem

[ttripp1]

After having replaced a bad EGR Valve and pressure sensor, my Explorer is now givng me a P0174 (System too lean - left cylinder bank).

Someone has told me that this could mean an O2 sensor has gone bad. Does anyone know how to find out which sensor would be bad? Or do I just need to pick and choose and start replacing them?

Thanks for any info!

Tim

2002 Ford Explorer XLS 4WD 4.0L V6 SOHC

 

[ttripp1]

Two shops that I've called have suggested it's indeed an O2 sensor, so I am going to replace the driver's side oxygen sensor tomorrow after work. I just hope that's it.

 

[Timoteo]

Look for intake leaks. If you have a leak you'll suck in more are then the MAF detects and your engine will be running lean.

 

[ttripp1]

Thanks for that.

I replaced the O2 sensor already on the driver's side. I got a P0133 yesterday after I got home from work (02 Sensor Circuit Slow Response) so I replaced the driver's side front O2 sensor.

So far, no more error codes. I do notice a little hesitation, however, when starting out first thing.

 

[ttripp1]

Well I've driven it a week and a half and haven't had a problem until now. The MIL is on again, and I have a P0174 once again, and a pending P0171.

I give up... lol. I'll take it to the dealership Monday. I'm going out of town this weekend (90 minute drive to my destination) so I hope nothing craps out on me while on my way.