Could a bad Catalytic Converter cause lean codes?

[Freakzilla69]

If gas had gotten into my cat and ruined it, could that cause lean codes P171 & P174?

[wiswind]

I am not seeing how.....if the catalytic converter is bad.....you should have inefficient catalyst codes.
In all honesty, the catalytic converters on our windstars are pretty reliable......
I replaced mine, on my '96 3.8L because the insides were rattling.....although they were still working just fine.....it was quite anoying.

The things that I would think of for the lean codes would be a vaccum leak......lots of places that can happen.....any vaccum line leaking.......etc.
Check the flex hose between the throttle body and MAF/air filter......including the oil breather line from front valve cover up through 1998, rear valve cover on 1999 and newer.
Also, check the IMRC.....if not working correctly.......1996-1998.....the vaccum actuated system can have leaky diaphrams = vaccum leak.....and they could be OPEN when they should be closed......
They are open when the motor is not running....held open by some pretty strong springs, and vaccum pulls them closed when the motor is running, until the PCM decides to open them under certain hard accelleration conditions.

On the 1999 and newer, the IMRC is driven by a electrical motor.......both banks by 1 motor......and the nylon clips can fall off.....leaving the IMR shafts to flop open and closed......even with 1 bank open and the other bank closed........

When the IMRC system is open at low rpm....it can cause a lean condition........and pinging.

Also.....dirty fuel injectors(s) can cause lean codes.
Even 1 dirty fuel injector.......the PCM is trying to ballance out the air/fuel mixture and is unable to do so.
A can of Berryman's B-12 Chemtool in the gasoline tank to clean up the injectors is a good idea once in a while.

Fuel filter been replaced lately?
Due for any other tune-up items?

That is a list of some inexpensive things that you can check.

[Freakzilla69]

I've rebuilt this engine from the block up recently. Almost all the vacuum hoses are new, including the PCV tube. The front valve cover tube was cleaned. I'm getting about 19 inHg vacuum at the upper intake maninfold.

I took the fuel rail off and cleaned each injector as best I could, I think I soaked the tips in Berryman's but I didn't take them apart other than off the rail.

IRMCs are new and functioning properly.

The fuel filter isn't new but it doesn't have many miles on it. The idle fuel pressure is good but I don't remember what it was exactly. Haven't load tested it.

I ran it with a bad missfire to get it home once, thought that might have screwed up the cat.

But the lean codes are the only codes it has.

[Jon04CTSV]

Any symptoms besides the codes?

[Freakzilla69]

Originally Posted by Jon04CTSV

Any symptoms besides the codes?

No, it runs great.

Right now it's parked, waiting for me to put a new torque converter in it. I'm debating if it's even worth it.

It's useless if it can't pass emissions.