Ford Explorer 4.0L V6 Sohc P0171 P0174 Lean Codes- Common Cause


Alright, guys today I want to go over another common area, I see for the cause of appeal 171 peel 174. Bank 1, & 2, lean and the Ford Explorers that the 4.0 liter sock engine is in them. This one, if you remember you see my last video I, put the PCV tube on it that was a month or two ago, checked it out afterwards, no problems, no with the fuel trims perfectly normal 6, 7%. And of course, we saw the tube was split in half from the oil being soaked.

And it's caving in it's, a very common issue on these there. Isn't, many other common issues on these two cause lien codes, except for the one on about to show you now I got to thinking it's got check engine light on it's been gone for a while we knew the fuel trims are just fine. When I left that PCV tube is definitely sucked in how could I have lien codes again, the intake seals on these aren't too common. They do happen, but they're, not to calm and that's.

The only going to happen when it's cold out. Yeah, to get freezing out, but I still don't think it's. The. Issue I looked at the mileage and then let's up here get the sticker, and guess what they just had an oil change and I knew exactly what it was immediately I just had to verify it.

Now, the problem is that went over here that checked the air filter as part of the wheel change service and then left the tube, which usually slipped right out here. They picked this up they're, checking the air filter. Anything almost, ok. And these tubes for the ventilation for the PCV system. They fall right out all the time. On here and I'm, one of the other models, there's, actually, two of them there's one here and one up here or right next to each other I wanted to, and those the same thing they fall out all the time and this is no big deal doesn't, really create a issue. The issue is as the air rushes past here, venturi effects picking up air and bring it in any kind of air leak after the mass airflow sensor is unmetered air, therefore the engines getting more air than what it thinks it's getting this only way it. Knows is by this sensor anything after this, a leak on this intake tube, a vacuum leak in the intake vacuum hose off the intake anything after the mass air flow, and it will incorrectly Meteor the air and cause lien codes all right, so I'm, not going to get too technical with this video I just want to show you how the PCM reacts once I plug that tube back in right now.

It's disconnected. You can see our short term fuel trims, right here just switching it right around. Zero is perfectly normal. Our O tubes. Our switch in it's, perfect mass. Airflow. Its point eight is about perfect point.

Seven point eight is good on there. Our long terms are a little high they're, not too bad. But obviously went to 15% or higher at some point to set that code up here, our barrel it's, really low it's 140.

Once you 158 for our area here, we're about six hundred feet above sea level. So this is way off and that affects the air fuel calculations also because this is basically only thing this thing is telling the PCM is where. The vehicles at as far as it's on top of mountain, where there's less dense air or two down by sea level, where there's the densest air. So it needs that calculation to be correct too. And it infers the barrel and almost all the vehicles, except for a few at the amount of super duties and stuff like that, almost all Ford vehicles, infer the barrel based off the mass airflow, reading being correct.

You can see how far off the fuel trims can get just by having that little hose off of there. So I'm. Gonna plug it in right now, and you can watch the o2 sensors, both of them pink one and Bank - they're going to go high in the voltage. And that means it's running rich. And then from there on out it'll start changing.

It will correct the fuel to get it back working start switching again, right, and you'll see. These numbers drop once these drop first it'll, start correcter than these later and I'm going to plug it in now I just plugged it in. And you can see right here, see when they went rich like that. First thing it's going to happen, the short terms are going to react, and then it's going to set the long terms, and it's to keep going down down it's me, slow to react at first that's. Why when you do this, you find the Pulse Indians running great. Now, you want to do a PCM reset, and it'll learn from there, and I'll show you how that looks because that'll also reset the barrel to a box stock, setting of 149, so we're going to do that.

Now, I'm going to reset the fuel trim back to zero, long-term and short-. Term, and of course that barrel back to 149 all right there we go. We got all the field trims back to zero. So I'm gonna start off fresh. And the bear up here is at 149, the base stock resets setting on there. And therefore it can learn from there fresh with the correct barrel, and it'll automatically update to the 156 158 for our area. But if you don't do this it's going to take forever, especially that Barrow to update, and you have to do a couple of full wide-open throttle driving to actually update it.

So it takes a long time the best way to do it is to reset the PCM while the engines off, and we can start fresh with an idle, and we'll see how it looks now, and you'll see from here on out these fuel trim to be below 10%, four, five, six, seven eight percent to pay in the age of the vehicle it's, just fine and already because you were heated up our o2 they're switching. And the thing to note here is that our long terms are zero. Perfect short term, six, seven, eight, nine percent in switching arrow. Twos.

Switching which means there's, no need for any further fuel, calculations Corrections because where it's at right now is make a no to switch. And that is just how simple it can be to diagnose drivability concern a check in July concern, a, you know, a lien Co concern.

Dated : 17-Apr-2022

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