I've got a 99 expy with a 5.4. It is currently showing lean codes for banks 1 and 2.
I've checked the vacuum with a gage, and it is showing a steady 20hg pressure. The only fluctuation is of course when I accelerate the engine. It ill drop a couple of hg, then go back to 20. when I let off it increases as it should.
Fuel filter has been replaced.
This has been a problem it has had for awhile, so I've been letting it sit and just using it occasionally to go to the store or something just to keep it in good condition.

For my question. Why do COPs cause lean codes? I'm pretty sure thats where the problem is going to be, but I need advice from the rest of you on this.
Today I took it on a 5 mile trip, and was standing beside it while it was idling. If it were a carburated engine, it made the sounds like one that is loading up at idle. I don,t think it is the IAC,, because it just don't have the same sound that I've heard from them in the past.
So this pretty much leads me to think it is a COP problem. I've never had COPs do this to me, but I have read here, the experiences of other people, that makes me think this is where it will end up.

Any thoughts on this will be greatly appreciated. I have no problem with changing the IAC, but I just don't think this what it is.

It has 145,000 miles on it, and has had a few Cops replaced over the years, but never all at once. There are no codes for a misfire.
So let me have it. I've just never really understood why the Cops cause lean codes..

Also if any of you think that it is the Cops, I need to be pointed to the best company to order from. I've lost my scorecard on the complaints about service. But if I remember right Uneek is the best place to get them.
Thanks in advance for input on this problem.

 

Tumba check the vac stuff that you don't normally think about. Like the brake booster and hose, and the vapor management system. Both of those can give you lean codes.

Of course you already checked the famous elbow, right?

Then there is any air leak after the MAF like the air cleaner tube and the gromet that seals the wires to the MAF. And an exhaust leak can do it too.

Just a thought.
Good luck
Jim

 

Why do COPs cause lean codes?

They can when misfiring , -because of excessive oxygen readings in the exhaust.

 

PCV elbow, my friend.

 

I didn't mention. It has the whole new Motorcraft PCV assembly.
I must have the wrong idea,so fix my thinking for me. I was thinking with the vacuum test I did, that I ruled out a vacuum leak. Because I have a steady 20hg of vacuum, with no fluctuation. Is my thinking flawed here? I thought that would mean I had the vacuum problem covered.
I did fix a couple of leaks before I got the vacuum test to hold steady like that. So I thought I had that one covered.

 

Jeese, So simple!

 

I havent even checked the MAf. I'll get that tody. Thanks.

 

I forgot to mention, it has been done. The soon to be Son Inlaw had that done, before he brought it back from Houston. But the Codes showed up again before the trip was over.

It seems to be still attached. Thought I never seen one as hard to get to as this one on this Eddie Bower

 

That's about it Tumba sir. - and why you fix the Misfire first , -if you have one.

 

Hey Tumba, -what are you doing ?

 

Hey Tumba, -what are you doing ? ?

 

Am i wrong in thinking that all of my vacuum leaks are fixed? I hook the vacuum gage up to any vacuum line, and get a steady 20 in of vacuum.
I've been over the system and can't find any more leaks.
I haven't cleaned the MAF yet. Will that help? Yesterday I drove it about 5 miles again, and it ran perfect. But when I got to my house with it, it was running odd again. At no time does it feel like its missing. But I'm getting the bank 1 and bank 2 lean codes. That is what has lead me to look at the coils. I looked them over yesterday, and everything under the hood appears to be in place, and no apparent vacuum leaks.

 

Usually when both Banks are positive for lean, - it's not the MAF, but clean it anyway. You have a leak , it doesn't have to be a hose or a line in your emission harness. It could be the IAT grommet or any of your intake gaskets. You have the 99 5four, therefore you have an aluminum PI Intake manifold. The intake gaskets are prone to leaking + the heads and intake itself are known to pit real bad. That model (5.4L's 97-99) also have a compression gasket between the plenum (T-body elbow) and upper intake that should never be used twice.

If you can't find anything causing this, you need to start from the manifold gaskets on up. Get little tank of propane and run a hose down onto the block cavity. Let the engine warm up to warm idle. Release propane and listen for a deflection in idle. With both banks lean, you should be able to find it.

 

Thanks. That's the type of info I was looking for. Because I just can't find any other problems. That's why I was thinking COPs


If I find that to be the problem I'll have to take it to a shop. That's more work than I'm physically capable of anymore.

 

I missed this post. Man just having all kinds of problems. Everything I own wants to break when I go through periods of physical problems and the demands of work. It's kind of like drowning, I can just barely keep my nose above the water.