Check Engine Light: Running Lean

[SEAN_VANCE]

Hello I have had a weird problem with my wife's expedition that is driving me nuts.

Check engine light comes on, code says its running lean, but no sympthom or anything bad....at least that I can tell....but the check engine light stays on....

Have taken it to two different mechanics, they cant find anything wrong with it....no vacuum leaks, computer and wires all fine, sensors all fine, not a damn thing, yet that light is on...

Anyone else have this problem? Its the 5.4 triton 1998 XLT

Any help appreciated!

 

[green03]

Are you getting 2 codes one for bank 1 lean the other for bank 2?

 

[grizybear]

On my 5.4 I had the same code for bank 1 & bank 2, and also a missfire on #4 cyl. I changed the plugs and put a new coil on #4. That took care of the misfire. But I found a vacum hose leak on the passanger side of the plentum (intake) I think it went to the Trans, it was leaking right at the 3-way connector hose deteriorated

 

[green03]

A leak is what I was going to point to as well. Anything that bypasses the mass air meter and allows air to get into the intake will throw this code. I was just curious because when this happens you usually get codes for both banks. Single banks lean codes can be something else like a plugged injector or something else....
Matt

 

[SEAN_VANCE]

I think its just one code ....thing is that my mechanic was the one who did the codes, so I dont know exactly, I may go to autozone and get the cod or codes and come back .....but i will try ur recommendations thanks....also, how difficult is to change the coils on these cars? another thing, dont u think that if it was a clogged injector I would feel something obviously wrong with the car..I remmember ahving a clogged injector in another car and u could feel it not running right...

 

[green03]

The lean bank code means that the computer has added fuel to the maximum of it's trim range. This can be caused by anything that is either adding more air than the meter is measuring (vacuum leak) or taking away fuel on that bank (reduced fuel delivery). You are right, a completely clogged injector would be felt, but dirty injectors (or a plugged filter) can cause the same code because the computer has to add extra fuel to compensate.

 

[JUST4FUN]

If it comes back both banks lean, mass air might be bad

 

[green03]

Originally posted by JUST4FUN
If it comes back both banks lean, mass air might be bad

I agree on this too, I have even seen an over-oiled K&N get the sensing resistors in the meter dirty and not measure the air properly......

 

[grizybear]

The coils are easy to change on the 5.4 if you can get to them... Cyl #7 is the worst (I haven't changed that plug yet). #4 is under a lot of hoses, but the rest aren't too bad. Just remove as much as you can above them to get room to work. they all will come out without removing the fuel rails. Doing #4 coil is how I found a vacum leak that was giving me lean codes on bank#1 & #2. It runs like it is new again (103k)
Hope this helps
Goodluck

 

[SEAN_VANCE]

Appreciate the input guys,

When you say mass air may be bad what exactly do u mean, what is "mass air"? is that a part that I can be changed? Sorry Im not too mechanically inclined.....lol
I only know some basics....but if you could explain it a little bit I should be able to understand what that is...

 

[green03]

the mass air meter is responsible for measuring the incoming air. on the stock setup it is inside the fliter housing between the filter and the throttle body. I would check for vacuum or intake tract leaks before I started looking at the mass air meter. Any air that can make its way into the engine without being measured by the mass air meter would cause this but it usually throws a code for both banks. The easiest way to figure this out would be to use a data logger on the OBDII port and see what is going on in real time. If it is only one bank going lean then it is more than likey not an air bypass issue. Injectors, O2 sensor for that bank, etc could be causing this. Where do you live? Are you near Houston? I have the equipment to properly diagnose this if you want.
Matt