I have a code that says Lean on right bank !! The problem is that both o2 sensors after the cat are showing up lazy. If it was an o2 sensor problem , then shouldnt the code be Lean on bank 1 and 2? I had these codes read at my tech shop,and they said there are many reasons that this code is there. The problem is that they dont have the same diagnostic equipment as Ford. They told me to see the Ford guys. So i phoned the Ford guys and tell them about the code and that i installed a K&N cold air intake 7 months ago. He immidiately said this could be the problem. Is this the case or ,because if it is i cant see K&N selling to many kits out there,if anyone has heard of this please let me know. In the mean time i am going to put the factory intake back on and have Ford scan for the problem. The truck is a 99 F 250 LD 5.4 2WD. Thanks

 

Post the exact code(s).

Usually, "lean" codes are due to vacuum leaks. Each bank has its own sensor. The intake could be an issue if there is an air leak after the MAF.

Downstream O2 sensors are supposed to switch slowly (if at all) if the cat is functional.

 

It's lean on one bank from the codes, though, not both sides. If it's an inlet vacuum leak, the intake kit, or the air intake being open from the MAF to the upper plenum both banks should show lean.

What makes one side go bad? Injector rail issue?

-Kerry

 

That is where the cofusion seems to be...if it is the intake kit ..why only one bank lean?? The injector issue was one option to consider according to the first tech. Its the Ford dealer who questions these intake kits.

 

Is it possible that one or more injectors are partially blocked on the one bank...had the injectors flushed a while back while trying to figure out a rough idle problem ....which still continues to this day..and that was before installing cold air intake kit.

 

You have several sensors working in conjunction to get the right amount of air/fuel to the cylinder. The 02, MAF, TPS, and temp sensor are the ones that I recall, right now, that all have input to the injector pulse width and cycle. Now there may be another sensor in the fuel rail like a pressure monitor or a fuel pressure line sensor( I don't have a layout and I'm going off of a guess). If any of these sensors gets crapped up or starts failing you could have a stumbling issue. You should have more codes, though, if these are starting to give you problems. Like an injector pulse width code for that bank. Isn't this grand?

I'm confused by your statement that both O2 sensors are lazy. Did you check output voltage on both and they were bad? If so... hmmm wierd...
I'd be tempted to swap out the one sensor with the code on it... then if the code comes back see below.

If your injectors are going bad or you have a clog... that's a possibility, but your fuel filter should have handled any large floaties. Your injector nozzles could be having issues. If the truck is running lean on one side you could pull the plugs (and I know how much fun that is) to look to see how bad it is by looking for the really white burnt carbon deposits of a lean condition. Then if one of the plugs isn't seated right (someone blew the plug out before you bought it) that could be a reason for a lean code and rough running.

-Kerry

 

It seems these newer trucks have more problems than Carter has pills!!! My Mrs. thinks i should dump the truck, I just had the head gaskets replaced,and heads planed and now it sounds like it could be more $$$$ just to get rid of the little yellow light on the dash! I think the FORD gods are testing me (all i have ever owned is FORD) maybe it's time to switch colours ( DODGE maybe ??? ) I can't believe i just thought that!!! I will see dealer Monday morning and let them scan for problem. Hopefully i don't end up going broke replacing sensor after sensor in the process of elimination game. (I hate that game), you would think after building a billion or so vehicles,they could get it right!! Well i guess i will see Monday morning. Thanks!!

 

Now, if you had said you just had the head work done in the first place, you would have gotten different advice....

I'd suspect an intake gasket leak on bank 1. Possibly a gasket didn't seat correctly or an injector o-ring didn't get seated properly. An exhaust gasket leak will also cause a lean code on a single bank. A well equipped dealer/service shop can smoke test the intake system and locate small leaks.

See my previous comment regarding downstream O2 sensors. Disregard it at your own expense.

Steve

 

Steve has an extremely good point about the head, the gaskets, and the o-ring... and the O2 sensors, so the O2 sensors output shouldn't be changing much, if at all.

Withholding information will always lead to incorrect speculation...

-Kerry

 

Sorry all ,but the code was up before the head work was started and remains after completed...and today i have found antifreeze leaking around the thermostat housing, and another fluid leak at front of engine...this is getting rediculous!!!!! I will be seeing shop where head work was done tomorrow morning before the dealer to see if they can explain these new found leaks. Thanks for the info.