Hi All,

My 2003 5.4L 140,000 just started idling very rough. About 6 weeks ago I had the plugs changed and shortly there after I replaced two COP's that were causing misfires. The truck was running very smooth for 5 weeks or so.

This week it started to idle very rough. It would stall if I stood still while in drive for any length of time. The RPM's would hang around 600 and the dip even lower. I didn't notice much of a problem while driving at speed. It's not as smooth as it should be, but it's not bad either.

It took two days before CEL came on. The code (AutoZone) said a lean mixture problem in both banks existed and listed the MAF as the probable suspect. I replaced the MAF and the problem improved maybe 5%. I chalk that up to having 140K without cleaning the original MAF.

I went back to AutoZone to get credit for the core charge and the CEL came on again, I figured I might as well get the codes read again to see if anything has changed. This time I got 4 of them:

P0171 - fuel trim bank one condition
P0174 - fuel trim bank two condition
P1131 - lack of bank one O2 transitions - lean
P1151 - lack of O2 switches bank two sensor 1

The common possible causes are vacuum leak, O2 sensor or injector problem.

Does anyone have any insight into what my next move should be?

Thanks much.

 

Have a dealer scan it.

 

When was the last fuel filter change?

 

April of this year. About 5K miles ago.

 

Factory O2 sensors at 140,000 miles definitely need to be replaced.

 

This is really good advice. I took it to my mechanic and he did thorough scan of all the on board computers. Checked out the performance of the O2 sensors while it was hooked up. Cool stuff.

FYI, the problem was the PCV elbow was shot. He didn't need the scan to determine that, just reached around and shook the hose. But I thought it would be a good idea to get everything checked out.

Thanks all for the suggestions.