Hello I still have my engine light on in my truck and the codes I am getting are P0171 - System to
Lean (Bank 1) and PO172 Lean bank 2

I have checked the MAF sensor which someone told me to check first and I cleaned it and reset the light and it came back on the next day.I really dont know much about these lean codes my truck seems to be running ok maybe it idles ruff sometimes and acts like it is going to die but it has always done that and it is not a big deal.

Does anyone have any advice on what I should do or check? Or any information on these lean codes and if it is harmful to my truck.

1997 Ford F-150 XL 4.6 flareside 4x4

 

lean codes mean air leak. look of small vacuum lines (black rubber- 1/4 inch) that are hard, cracked or brittle. replace them. intake manifold gaskets can also leak- any oil residue noted around them ? gaskets are normally a 6 cylinder thing, but possible. look for the bad hoses.

 

FordMan

I had the same codes for a long time. 3 weeks ago the truck would hardly idle, had no ability to accelerate. I decided to park it, and check everything. Some of what I did won't apply to the lean codes but apparently something did, because it's fixed, and has never run this well since I got the truck.

Your code implies a problem after the MAF sensor. Regarding that, this is what I found on mine.

1. The pcv line is rigid plastic, but the ends connect with rubber hoses. If the pcv is good, check both ends of the line. On mine, the pcv hose at the valve cover was kinked tight and cracked, the rear hose was good. Replaced.
2. The EGR held good vacuum, but the gasket was leaking, and the EGR pipe to the exhaust manifold was cracked off the fitting. Replaced the pipe/fitting.
3. Rubber line from the throttle body housing to the EVAP was hard, brittle, and cracking. Replaced.
4. Rubber lines from the DPFE to the EGR pipe had cracked ends. Replaced
5. Hose connections into the air intake duct work didn't come with clamps, but seemed like they should have some. ANY loose joints here can cause the problem.
6. Double check the duct work. Any misfit here can cause an air leak.

Before doing anything, engine vacuum was 15" and a little floating. After doing all the above, 19" and steady. ( no codes of any kind).

Dave

P.S.- I did use a new diagnostic tool to double check the engine and PCM, but it didn't come until AFTER I repaired the truck. It's called OBDCOM. installs on a laptop and can be plugged into the DLC. It's extremely handy because you can monitor multiple sensors, rpm, temp, speed, etc... Wish it would have come a few days earlier. Instant error code listing and explanation.

 

Some good information guys and I thank yeah I will start checking this stuff tomorrow sometimes it sounds like something is sucking air around the intake so maybe there is a cracked hose.I bet it has been going bad for a long time and I am just use to the way the truck runs so if fixed it may run like a new truck...LOL

 

Ford Man10

Just a couple of notes. On my truck, the EGR pipe leak wasn't readily visible because the heat resistant shroud had slipped down on top of the fitting/exhaust manifold. I saw that problem right away by just sliding it up a couple of inches.

The PCV hose kink was concealed by the insulating foam cover. Peeling that back a bit exposed that one. I had always pulled the PCV and shook it to see if the check valve was working, but that doesn't check the ends of the hose connections.

I used MAF spray cleaner after testing that. A small amount of road film/dirt can give faulty readings. ( also went back to the stock type air filter. Had been using a K & N).

I also changed the fuel filter after testing the regulator. It was due for a new one.

The TPS passed one test and failed another (voltage at WOT), so I changed that. Although with the voltage not increasing as the throttle was opened, it seems like a code should have been tripped, it wasn't. So my reasoning was, the PCM had no idea what to calculate as a fuel charge. So at WOT I may have been getting only a partial fuel charge, which would have caused a lean mixture. By the way, I did change the plugs and wires. They were due. The color of the plugs seemed to show a pretty consistent lean condition, otherwise normal wear on the center electrode.

If you have access to a vacuum guage, check the readings at both ends of all the lines. With some adaptive hoses/fittings you can fit all of them. A big drop at the sensor/valve end might indicate a leak along the way, maybe a rubbed through spot.

Lastly if you do change a few things (bad or not) like plugs/wires, sensors, or clean a few things, expect that maybe the truck will still run a little poorly for 2-3 drive cycles while the PCM relearns some readings/values.

The OBDCOM diagnostic tool/software helps a bunch with some of this, because it can be used to check the engine in real time, while it's running, or better yet WITH SOMEONE ELSE DRIVING, sit in the other seat with a laptop and check stuff while you are going down the road. Pretty cool.

Dave

 

Was thinking about getting this tool OBDCOM diagnostic tool/software seems like a good deal.Thanks for the info.Just wish I knew more about the vacuum lines and where to start looking on these trucks.Do you know where I can find a diagram or something on the location of all the vacuums?

 

FordMan10

Well, most of the pollution control things should be detailed on a factory diagram decal, usually on the fan shroud ( color coded plastic lines mostly ). As for the rest, the fuel lines are typically all steel or braided steel, so just about any rubber or plastic tubes or hoses are for vacuum. A lot of them will originate at or around the throttle body housing.

Most of the hoses I've found that were in really tough shape seemed to be at the rear of the engine, and fairly close to the firewall. Every where else, the problems weren't as bad, but did include split ends or occasional kinks.

Dave

 

Ok thanks Dave I think the sucking sound seems to be coming from behind the throttle body so maybe it is around there.I know when I went and got my oil changed one of the guys who was working on it knocked a vacuum line off around the throttle body and the truck would start then die real quick and that caused the engine light to come on maybe it is that same vacuum line and it is now cracked or loose and it is getting enough vacuum where it is not causing it to stall.