4.0 ECM troubles

[Barney0024]

Look for leak(s) at the intake manifold gaskets. This can cause a vaccum leak resulting in a lean code for both banks. Spray brake cleaner or starter fluid where the gaskets are with the motor running. If Rpm goes up, thats where your leak is.

I replaced those gaskets and my truck runs great now

 

[holmes1]

Look for unmetered air getting into the intake from either a broken vacuum line or a line not connected up.

Bird

I used brake cleaner this morning looking for a vacuum leak. I found no leaks, and all of the rubber seems to be in good condition, soft and pliable. I got a can of MAF cleaner, and cleaned the sensor. I also cleared the codes, and drove it a bit. The codes haven't returned, but it still idles poorly in drive at the stoplights. I'm convinced that the codes will return.
DM

 

[Barney0024]

I had a difficult time finding the leak on my truck. Test it again. I ended up having a friend of mine who work at mazda take a look. He found the leak. It was a sneaky one

 

[holmes1]

I had a difficult time finding the leak on my truck. Test it again. I ended up having a friend of mine who work at mazda take a look. He found the leak. It was a sneaky one

Could be. I'll try to get the codes back today. I also have found that if I put it in neutral, and floor the pedal, it will only get to about 3,000 rpm. It runs really rough at WOT. (in neutral) However, when I'm on the highway, it will go way past 3,000. Maybe it's supposed to not scatter in neutral.
DM

 

[Donnie strickland]

Your truck has a rev limiter when in neutral (or Park, with A/T). It cuts the spark when you get to 3,000 rpm; that's why it sounds like it's running rough when you do this. It is.

 

[holmes1]

Look for unmetered air getting into the intake from either a broken vacuum line or a line not connected up.

Bird

The codes are back again. If it is a vacuum leak, it would have to be significant. I'd think that I would be able to find it easily with ether. I'll try again tomorrow.
DM

 

[MAKG]

Lean codes can be caused by a number of things, including a vacuum leak. They can also be caused by things like misfiring, poor grounding, or burning coolant.

You're going in circles; I think you need a (good) shop.

 

[holmes1]

Lean codes can be caused by a number of things, including a vacuum leak. They can also be caused by things like misfiring, poor grounding, or burning coolant.

You're going in circles; I think you need a (good) shop.

Well, I found it. It was a large rubber elbow at the front of the intake. Part of the PCV tubing. When hot, it would open up at the elbow, and suck a LOT of air. That piece of tubing was still $47! Thanks, guys
DM

 

[MAKG]

Well, PCV tubing can often be made using bulk emissions tubing. Though if it's through a really tight spot, you might want the custom molded version.

 

[holmes1]

Well, PCV tubing can often be made using bulk emissions tubing. Though if it's through a really tight spot, you might want the custom molded version.

That's what I got. The $47 part was molded plastic, 90 degree elbow, with a rubber elbow on each end. The new PCV was an additional cost. Ford doesn't give anything away.......