New to the thread and site. Good info, and I am having same issues. I have a 2001 f150 5.4 xlt screw. I did the tune up, plugs, cop's, changed three injectors, 4 new cats. And it still giving code p0172. Says its rich not lean. Change hoses, vacuum lines. And still idles rough when its put in reverse or drive. Put scanner on after putting new injectors. And said catalyst was inc. And all 4 of my o2 were inc. I see several threads about IAC and egr should i change that as well? Put new crank case hose and fuel seperater house ( dealer parts) is there anything Im missing. My mechanic thinks I need a new timing set, but I would like to try and solve issue before tearing into the block. Thanks

 

Indeed the 172 is a Rich indication on one bank.
Working on intake vacuum hardware is not the cause of richness.
It's excess fuel for some reason.
Have you checked for a leaking fuel regulator through the vacuum hose into the intake?
Only three ways to get excessive fuel.
Those are excessive fuel pressure, leaking regulator and a leaking in injector.
Timing won't be a cause either.
Remember, that bank's Ox Sensor detects it as not enough oxygen in the exhaust gas after combustion.
This shifts the long tern fuel trim table lean and sets the code.
Do not guess about anything.
Good luck.

 

Rich is too much fuel or not enough air

Could be something restricting air movement like a collapsed last adjuster, worn camshaft, timing issue on one bank etc

I'm guessing you only have a P0172 and not an additional P0175?





As for forum etticuit, we ask that you have one thread per subject, it can get confusing to have your help in multiple places

 

Yes it only po172 is the only code its giving. We've check all the hoses non are collapsed the ones that were i replaced. When we did the tune up it rain good for a little while and then started doing the samething. We've check the injectors after i changed 3 of them dont see any leaks. Have changed to o2s yet. Changed all 4 cats as stated because on side was clogged. So im not sure it my o2s are deffective from that. Just go through the process of elimination.




sorry wasnt trying to post so many times. Just trying to get answers. Thanks for all your help.

 

Have you checked all 4 injectors on the passenger side? I'm guessing that was the side with the clogged cats?

 

Your kinda going around the Bush as they say.
Get hold of a Scanner and look at the Ox Sensor2-1 voltage swings and compare it to the other side.
It may be contaminated or lazy.
You have to see the issue and not keep hoping , guessing and replacing parts trying to get lucky.
Did you check for gas in the regulator vacuum line?
Imagine if you paid a repair shop to work this way.
You would scream bloody murder at the bill and outcome.
Good luck.