PLEASE HELP!! 4.0L Too Lean Problems

[mrslurp]

I am having problems with my 4.0L Ranger. I keep getting the too lean codes P0171 and P0174. At this point, I have cleaned my mass air flow sensor, replaced the fuel filter, cleaned the K&N filter, and checked all my vacuum hoses. Whenever I am going down the road at say 40 MPH (it can do it at any speed), and just push down the gas a very little, sometimes I get this vibration. If I either turn the over drive off, or just push it down further, the vibration goes away. It seems that if you go to a higher RPM it runs fine. It has been like that for the last 2 weeks since the light came on. Any ideas? I leave on a 400 mile trip next week, and I don't want to have a truck not running at 100%.
Please help.

 

[gijoecam]

Assuming it's the 4.0 SOHC, you have an intake leak somewhere... It could be as simple as the oil cap being left off, or it could be the infamous lower intake manifold gaskets leaking like they all do eventually. Those are the two places I'd put my money.

 

[4x4xbrian.com]

cyl misfire

its skipping, thats the vibration, check spark plugs and wires. and that gives codes for too lean also.

 

[mrslurp]

I didn't see anything about the plugs/wires causing the code when I was looking online, so I will have new plugs/wires put in ASAP. I actually just bought Bosh Platinum +4 spark plugs and 8mm wires, but when I went to change them, it became a pain in the ass, and the lack of tools basically had me replace 3 wires and that was it. Since I work 11p-7a, I will have to make arrangements with the garage. I made some calls today, but seems everyone is closed or full. Any other ideas if this isn't the problem? I mean other than that vibration when you push down a little bit on the gas while driving sometimes, it doesn't seem to be running bad. I have been driving it for a couple weeks like this. Thanks for the help.

 

[mrslurp]

I just had the plugs changed with Bosh Platinum +4's, and 8mm wires. Still have the exact same problem. What is the next step?

I took it to the Ford dealership, they charged me $250 to replace the PCV valve (they said it was cracked), changed the fuel filter, and to read the error codes P0171 & P0174, which I told them that before I took it in there, as I have my own reader.

I just had the plugs and wires changed.

The Mass Air Flow Sensor was cleaned with MAF Sensor Cleaner from the auto part store.

Now what?

 

[gijoecam]

Lower intake manifold gaskets, or some other vacuum leak in the intake. Lean codes aren't caused by oxygen sensors, they're detected by them. Lean condition is usually caused by one of two things: Too much air (vacuum leak) or too little fuel (fuel filter, pump, regulator). The most common culprit causing fuel starvation is a plugged filter, but the most common cause of a lean code this time of year is a vacuum leak caused by the lower intake manifold gaskets. Unless they've been changed to the updated parts, that's where I'd put my money.

 

[mrslurp]

I am starting to think the over drive is the problem of vibration. I thought the plugs would fix that, but it doesn't. I actually took the time to go over the gears and drive slow, etc, and it seems the only time I get the vibration is when I am in 5th gear (over drive). The truck is an auto. When I turn the OD off, I don't get the vibrations, but the OD should not be causing the too lean codes. Is there anything I can do myself to check the lower intake manifolds? I do not have a garage, but a small 2 car parking lot, I have basic tools, so is there anything I can do to test?

 

[okieranger]

My 97 mustang did the same. Turns out that changing transmission fluid and filter cured it completely.

 

[kaexp00]

I have same codes

I have a 2000 Eddie Bauer SOHC 4.0 166,000 miles and got the same codes. My MX told me to try some fuel injector cleaner and I did. Got them again. Just had my brother check with his scanner and clear codes. driving two days and they haven't come back. I don't like hearing that the lower manifold gaskets may be causing vacuum leak but that is probably right. I have the same vibration/growling but at idle and fear that may be transmission related. How do you check the manifold gaskets for vacuum leaks. I almost afraid to hear the answer.

btw THANK YOU to everyone on this site. I have already fixed a couple of things and am working on a few more. I am going to join the elite for sure. More than worth the experience and advice given here.