You still have a vacuum leak.
Look again.

 

I've had several lean codes on my truck. Everyone was caused by a vacuum leak.

 

PCV hose elbows are real common for going bad.

 

Check fuel pressure.....The computer knows how long to open the injectors based on a specified pressure that it expects to have available. IF your pressure is less then that, not enough fuel will be sprayed into the cylinders causing a lean code. Could be a hanging injector on that single side. Doubt it's a MAF. that would cause banks 1 and 2 to be lean, not just bank 2. I would say if you have the ability to, watch your O2 sensor PIDs. It could be an intermittent drop to 0v, on your Bank 2 o2 sensor, thus causing the lean code.

Being able to watch your sensor's and their outputs makes diag. of these issues soooo much easier!!

 

I did some more poking around tonight. I checked the pcv valve and that was working properly. I then checked the lines coming off of "tri y" fitting that attaches to the pcv valve. Sure enough one of the hoses had a hole in it. The one that connects to the intake manifold next to the throttle body. I also replaced another hose that was showing signs of wear. I couldn't tell if there was a hole or not because it ripped in half when I removed it.

Anyway, I checked the rest of the vacuum hoses and fittings and they all seem ok. I guess I'll have to wait a few more weeks to see if it is really fixed this time.

 

Hi all,

To say the least, this thread and this board has been extremely helpful. I've got an '02 4.2L V6 F150 Extended Cab. The "Service Engine Soon" light came on about 2 weeks before Xmas but everything sounded fine. After finding this forum and reading some of the threads, I ponied up and bought an OBD-II code reader (Harbor Freight had them on sale for $40 last weekend).

I'm posting in this thread because I got the same P0174 code. I attempted the first suggestion (and the easiest) and cleaned the MAF. Cleared the code and everything was fine until the light came back on yesterday.

Couple of questions... If it were a vacuum leak, am I right in assuming that it would be somewhere between the air filter and the throttle body? Regarding Wilber15's instruction to "watch your O2 sensor PIDs"? That requires a bit more than just a $40 OBD-II reader, right?

I'm sure these are noob questions. I typically don't work on cars or trucks but since I do do my own maintenace on my motorcycle, I figured I'd give this a shot. Thanks!

 

The MAF can NOT cause a "lean" code on a single bank. It will affect BOTH banks equally. Don't waste the time messing with the MAF if you have a single lean code.

Single MAF codes are almost always due to an air leak that affects one bank more than another. The include intake vacuum leaks, exaust leaks (upstream of the first O2 sensor), and possible injector faults.

By far, the most common reason for "lean" codes is, as already stated, intake vacuum leaks. This cannot be emphasized enough. The PCV hose elbow, common to all engines on this platform, share this common failure item.

The inexpensive code readers cannot read PIDs or present freeze frame data. Those scan tools are in the $200-300 range typically (ie, Actron 0145 or 9150 or comparable). I use an old laptop with OBD-II interface that does do all this ($120s from Alex Peper).


Steve

 

Thanks Steve. Is the "$120 from Alex Peper" from www.obd-2.com?

 

It's been a week and so far so good.

I'm keeping my fingers crossed but I think changing the pcv hoses fixed it.

 

My 2002 F150 V6 did not have a PCV, but it did end up with bad gaskets between the plenum and upper intake. I tried to get the plenum off, but could not reach tha back nut. What tool is needed?? Ended up taking it to FORD and $374 later fixed. The changed the gaskets and did an induction service (cleaning injectors). The also saw that the spark plugs were fouled. I was able to do that and save me $168.


Where does one get tools to remove the plenum?

 

i had a difficult time figuring out the lean codes on a mans 97 F250 w/5.4. After checking all the vacuums and everything checked with snap-on scanner,fuel pressure o-k, volume o-k; wound up just pulling the fuel filter, shook it real good and poured thin mud out! It seems it took a while of driving for the sediment to collect around the element and lean it out. I was even told they put a filter on about a year ago. the guy was probably lied to since they are so damn hard to change

 

i have pulled both codes multiple times....lean bank 1 and lean bank 2

could it be because my exhaust manifold is broken and i have an exhaust leak?

or is it something else?

THNX
Duggy

 

My situation required me to take my truck to Ford and have them replace the manifold (plenum) gaskets. They indicated that this is common. If you have the proper tools you could do it yourself, but I could not get the back plenum bolts off. The parts were around $80. Good Luck.

 

2005 F250 Super Duty, 5.4 l. V8 77K miles. Northern Michigan.

Bank 2 lean code, three times. Not missing. Truck is in a heated garage and only outside during the day at work. Occurs in very cold weather, so, I put in dry gas and injector cleaner. Continued with dry gas at every fill up. Usual procedure in the winter. It was good for over 2 months. Now the air temps are in the single digits and the CEL came on for the second time. Repeated dry gas and injector cleaner and only worked for a week this last time. So, three times. I am going to check the vacuum lines as suggested.

Thought it might be water in the gas.

Just joined this forum. Thanks.

Walt B
MI/USA

 

I have some comments to make concerning the use of Drygas.
You must understand the Drygas treatments takes up moisture in the gas as it's supposed to do but has side effects. It dosn't just disappear.
The big 'but' to this is it leans out the gas for combustion and will make a lean issue even worse.
Most of the gas now days has Ethonal and is already leaning out the gas mixture without adding more to the issue by excess use of Drygas.
Do not keep using Drygas unless it is needed on a singular.
Doing so absolutely kills fuel mileage worse than the cold temps already does.
A stack up of all these effects can cause the fuel tables to shift out of limits setting a lean codes. Then add an air leak on top of it yet, if one exists.
If water is in the gas to often change sources.
Good luck.