Hello All!

I just got a new 96’ f150 and its my first gas truck and i have some issues that I wanted to get your opinions on. So i’m getting a lean code and bank codes, with a MAF code as the cherry on top. The issue at the present is that when I start it I gotta let it beep three time, crank it up, then you gotta rlly give it some gas or once you get going a little it’ll stall out. But after it warms up it has a really rough idle, when I stop at a light or something and about to come to a complete stop, itll shutter a lil and just starts shakin. I assumed it was a fuel pump so I switched between tanks to see if one was better than the other, but they both performed the same, threw some sea foam in there to see if that would do anything. I’m hesitant to say it’s the fuel pump, due to both working about the same, I took a look at the fuel filter and it looked relatively new, but i got one on order just to be safe. I’ve also got a new MAF coming in today to see if that’s the solution, but outside of that i’m not quite sure what it could be. Any words of advice would be super helpful!

edit: Oh and the EGR diaphragm has been replaced recently and so has the Idle air controller.

 

Post up the code numbers you are getting. Good chance you have a MAF problem but it could be a combination of different things too, Any exhaust leaks?

 

Shorted O2 sensors could be the issue too.

O2 sensors do not last forever and I hate swapping parts unless I diagnosed them bad, but I would certainly replace the O2 sensors if they have not been done in the last 100k or so.

 

Thanks for the reply!

Last owner said there was an exhaust leak, I can hear it but haven’t pinpointed it yet. Could that cause an issue this bad?

Codes are p0171 p0102 p0113 and p0174

Codes are

 

Exhaust leaks upstream of the primary O2 sensors can cause a lean condition because fresh air can be drawn in in between exhaust pulses and that messes up the O2 readings.

 

Well after further investigation it seems that the previous owner has removed the cats entirely for some reason, he also took what I assume is the EGR tube and welded it closed and onto the new pipes. I assume this is the cause of my issue.

 

EGR on the V8 motors is at the front of the engine, the only tube at the back would have been air injection but I didn't think that was necessary on OBD2 trucks.
A missing cat will not cause a lean condition as long as the exhaust is sealed up air tight.

 

I’ve got the L6, or were you saying that problem would only happen on the v8’s?

 

No that applies to all engines.

 

If you unplug the O2 sensors you will know very quickly if that was the issue. YOur truck has vacuum lines, take pictures of the ones you can see and post them. I notice there are NO PICTURES here, I almost guarantee that is your issue.

 

Correct me if I'm wrong, but wouldn't fresh air being pulled over the O2 cause it to run richer? Because it would think it's running lean, and try to compensate with more fuel?

 

You would think right... but somehow it trends the other way. I think it's because the computer is actually seeing the rich-lean pulses and perhaps when it goes rich it's way too rich which then forces it to pull out even more fuel and overall the engine ends up too lean.

 

Interesting, so I wonder if there's a combination of rich/lean issues going on here. Like the motor is actually running rich, but the computer thinks it's running lean due to the exhaust leak.

We'll see where he's at with the new MAF.

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Since there is a TSB for 1996s and MAFs I will go ahead and agree it is worthwhile to check another one in its place. but no amoutn of MAF or o2 sensors fixes the many feet of vacuum leaks it probably has

 

As suspected new MAF did nothing, gonna smoke test it and see where that leads.

I thought I could escape my vacuum leaks by switching bmw to ford, but was I ever wrong.