I am new to the forum, and have a problem with my 98 F150 4.2 I cut the cat converter off , it was all rusted out, loud. Check engine is on, has been on before I cut off cat. I had it checked at auto zone. It came out with 5 codes, PO171, rich or lean condition on one bank only. PO174, rich or lean Air/fuel ratio, on engine bank 2. PO401, too little flow on EGR system. P1151, ECM could not adjust fuel trim because of lean or rich condition. P1131, ECM detected bank 1 02 at its lean limit. The truck idles rough in gear when at a stop, but idles fine in neural or park. Do you think if I replace the EGR valve it will fix the rough idle? I don't know much about this.


Thank you for any help


Rick

 

Have you cleaned the idle air control valve, mass air flow sensor, or the throttle body? Had this same problem cleaning these fixed it for me, just out of curiosity does it stall when stopping and stall more when stopping down a hill or incline ??

 

No, I have only cleaned the throttle body. I will try cleaning MAF sensor, and idle air control valve. Where is this located ? I am not familiar with this. To answer your question, it does not stall, but almost does,runs rough and shakes at stop light on level ground. Thanks for the advice

 

Mass airflow sensor is located inside the thing that holds the air filter so when you open that container you will see the air filter on one side and a plastic piece on the left side pull that out and disconnect the wire

The iac is located on top by the throttle body it has 2 bolts holding it

This is all on google as well so if this is too confusing. Make sure you use the appropriate cleaner for each part. Mas cleaner for mas and throttle body cleaner for throttle body and iac
Make sure the the throttle body cleaner will not remove the coating on your throttle body as this supposedly will ruin it.

 

FIRST thing to do is check for vacuum leaks. All those lean codes probably indicate a major leak.

The EGR code is usually caused by a bad DPFE but can be anything preventing the EGR valve from opening or a blockage in the EGR passages. Pull the vacuum line off the EGR valve when it's idling, connect another hose to the valve and suck on it. The idle should get rough and may even stall if the EGR valve is okay and the passages aren't blocked.

 

This is very similar to what I had and I had no vacuum leaks. There is a pcv intake elbow on this truck that commonly leaks check that and work on cleaning the sensors first as they might be part of the problem and it gives the truck back some kick that it's lost over time

If that doesn't do it take it to a mechanic and have them check the vacuum. There are a few methods that you can do this yourself but they are very dangerous and can catch the truck on fire.

 

This thread is getting really 'rich'.
You do not understand what the codes mean.
Until you do and correct the issues, the idle will stay rough and drivability will suffer.
ALL the codes except the 401 are associated with each other.
171/174, 1131/1151 are all caused by the same fault. An air leak.
The air leak shifts the fuel tables causing the roughness and all the codes.
This is common to the v6.
Do some searches the see the sources and what has to be done.
.
401 is a lack of flow failure on a test of the EGR system the computer does two times in each drive cycle..
Good luck.

 

Shane, the 4.2 V6 doesn't have the same elbow that the V-8 does at the back of the intake, it's a pretty straight shot from the PCV valve to the side of the intake.

As Bluegrass is hinting, it could be leaky intake gaskets.