HI Everyone: This is a 2001 Ford Expedition with a 4.6 liter engine.

No complaints from the customer other than the check engine light is on.

This video shows you how to follow a diagnostic process and solve the problem.

Transcript: Ford P0171 and P0174 System Lean – Check Engine Light On

Everyone, we’re here at John Sadler’s Auto Repair. Today we have a 2005 Ford f150 4.6 liter, the customer’s complaint after the agent warms up, every time it comes to a stop sign the agent stalls, it’ll be the restart drive. Okay, every time he stops, it’ll stall. When it’s cold and won’t stall. I’ll show you what I found out.

We had diagnostic code a P, oh 506, unstable idle. And I’ll bring the camera to show you what I found out. I drove a dries pretty good to give you all kinds of different possible causes. And so we got an air intake restriction, exhaust restriction, mechanical fault, sleds throttle, body damage, electronic throttle body damage, PCM.

Well, I found a technical service bulletin on all data. And I’ll show you that. And they want you to remove the throttle body when it gets sliced up. And they want you to take a Q tip, you know, brush and clean it. And that’s a lot of work. So I look at the vehicle, I took the air filter housing off.

And when I took the air filter off, they didn’t get it all the way in, you can see how it’s all smashed. So it’s not supposed to look like that. If you compare it to two new ones side by side, so dirts getting past there. So there’s a little sensor inside of here, a little hot wire for the mass airflow sensor for the speed and the temperature of the air going through. So we’ll clean that.

And CRC company makes a pretty good brand of mass airflow cleaner. And then instead of taking shop air, which is full of oil and dirt and everything, I use this auto duster, it’s just clean air, like computer air. So I went over to the throttle body. And man, that stuff’s it’s got a carbon buildup everywhere in there. That thing is in really, really bad shape, it has a lot of bills up behind that plate.

And it’s like little Craters of carbon is so thick behind the plate. So when you just have the plate closed, you can see some buildup on the front. But when you open it up, and you see that big black area, that’s really bad. So take one more look inside there. So that’s a lot of build up. It’s really thick.

So that’s what our problem is. So you always want to take time, in closing here to look at the code, see what it means. Lately, a lot of consequences are coming to me and saying they go to shops, no one test drives their vehicle. I always test drive people’s vehicles, one of the first things I do.

So a lot of times the consumers still here, I’ll go for a test drive with them, which I did with this consumer. And every time we came to a stop install, so we could verify the condition he was having it for sure. No second guesses about it. Then we had the all data information.

It’s the same as it comes from Ford is things outdated just buys it it scans it on the internet, and then it’s updated very frequently. And I also remember for two websites, I ran the VIN number and there’s no recalls no service bulletins, no outstanding issues for this particular vehicle. So we’ll do our BG fuel injection cleaning, put it all back together and we’ll have another satisfied customer John Sadler. Thank you very much.