Results of Code P0171 and P0174 - 4.0 Liter

[George]

Here is a copy of my original post for reference:

I also have the lean codes on both banks. Driving me crazy. I an used carb cleaner at all vacuum joints with no change in engine performance, found a loose O2 sensor on left bank and tightened it, cleaned MAF twice.
I have noticed that it only happens when the engine is at idle and the truck is not moving, however if I let it sit for hours just idling there are no codes. Only when driven and coming to a stop. I can get it to come on when it is warmed up if I raise the idle to 2k and wait 15-30 seconds then let it idle.
Where can I find the normal sensor read data to compare to what I get? MAF is about .35- .39 at idle.
Thanks

Now here is the work described and the results obtained:

1. Cleaned the MAF several times with no changes to performance.
2. Collected information with tool on when , where, conditions of code.
3. Read alot of forum information here. (thanks everyone)
4. Inspected O2 sensors and found bank one was actually loose. Tightened it and found the codes showed up less often.
5. Sprayed all the intake and vacuum lines with carb cleaner. No change in idle performance.
6. Did find air intake plenum (between filter and throttle body) have pipes connecting it to valve cover and they were loose. Put clamps on the connections. Now codes are registered but no MILF light. Improvement.
7. Based on codes only being introduced during idle and only after being at a higher RPM first. (coming to a stop light) I thought must be PCV valve system leak. Removed all piping for PCV and did find a defect in the elbow from the throttle body to hard pipe. (inside of bend, hard to see without removing) Had to use a water pump bypass hose to replace the elbow. Replaced PCV valve while I had it apart.

BINGO!!! now all injector readings seem normal, secondary O2 sensor reading are more stable, and after several hours of in town driving (stop and go) there has been no more codes.

Thanks to all on this site for the informative posts.

George

 

[Sasquatch_Ryda]

On an SOHC it is almost always that elbow on the PCV, glad you found it.

 

[jmg8550]

If it is a OHV engine, I would bet you have cracked heads. Mine threw those same codes for a long time until the heads finally gave and filled my crankcase with coolant. Are you mysteriously losing coolant too?

 

[Sasquatch_Ryda]

If it was an OHV I would bet it was intake gaskets leaking...

 

[George]

Gentlemen,

I was just posting my findings and final solutions.
My hope was to pass on what I learned so other would have an easier time troubleshooting.
Thanks for reading

George