The other night, whilst pulling a hill I had codes 0156/1131/1151 come active. I experienced huge lack of power, and almost a misfiring type feeling. I then cleared the codes, and the truck drove good for around 10 miles. I then had codes 0171/0174 come active.

Now not wanting to just end it there, I cleared them, and drove a short distance more till they came active again. I know both codes mean banks 1 and 2 lean, as that is what the 3 previous codes were pointing to on bank 2.

I've checked my MAF, PCV, and don't really notice anything wrong. I sprayed my MAF down with non film electrical cleaner, and tried that. Seemed to help abit. Now when I drive it, it will hesitate for only a second or two. I've also checked over all of the vac hoses, and it seems to have great vac at idle(have not put a gauge on it as of yet). Now, it almost seems as though its fuel related(pump). The truck has a new set of injectors roughly 10,000km ago(misdiagnosed miss). What should the fuel pressure be at idle? And also, should I be checking the DPFE sensor? I will also be replacing the fuel filter, and pcv tomorrow.

 

I had a 2001 4.6L with similar issues. I had done the same things. Replaced the pcv and hose, fuel filter, the vacuum harness for the 4wd(broken hose), cleaned the MAF, and check all vacuum lines(no issues). For me it came down to the o2 sensors. I replaced the 4 of them, and the issue went away until the new o2 sensors started dying(aftermarket cheapies). I returned them and got my money back. I ponied up for the motorcraft o2 sensors, and it ran without a hitch. Then I traded the Scab off for a new 2011 Screw(needed more room for the family). Good luck in your search as many scenarios can throw the lean codes.

 

And thats where I'm at right now, so many possibilities. I just can't see it throwing both bank 2 O2 sensors, then when I clear it, throwing both banks lean. Today I just replaced the fuel filter, PCV and hose, as well as the DPFE(due to the pins having very light corrosion). But to no avail. The problem is still there, but its very intermittant. From a stop, to 120km/h the problem(lack of power) will only happen for 2-3 seconds intermittantly. I'm going to have to check the fuel pressure at idle, and check it while I'm going through gears. I have a feeling its the pump, because I can't see the O2 sensors going intermittant like that.

 

Well I just checked my fuel pressure, I have 30psi at idle, and a hair under 40psi with the vacuum line off the fpr. I am at a loss with this problem. I changed the front two 02 sensors, and it hasn't made a difference, I just disconnected the battery for around 20 minutes to reset the pcm manually. I will see if the problem comes back.

 

I know you said you checked the PCV, but did you check the elbow behind the intake carefully?

 

Yes, I removed the pcv hose and inspected the whole thing. Its in good shape.

Update: After I replaced the DPFE sensor, and pcv valve, I checked for any vacuum leaks, I could not find any of the sort, so I said screw it and replaced the two upstream o2 sensors. It made the problem better, but did not fully fix it. So I went ahead and replaced the two downstream o2 sensors as well. The truck ran 100% for about 10 minutes. I then proceeded to throw codes p0155(upstream heated element) and p1100(maf intermittant). I stopped and the truck just about fell on its face. I popped the hood and wiggled the connector on the MAF sensor, and I could replicate the problem. Once I got the truck home, I inspected the harness side connector, and the pins seem tight, but the MAF side seems worn. So I will be replacing the MAF sensor.

That brings me to question #2, have any of you had any luck with aftermarket MAF sensors such as the granetelli one? Or is it better to just replace it with the stock ford one?

 

Stick with stock.

 

Another update. I replaced my MAF, and while doing so, I found that the extension harness for the MAF had a rubbed wire on the B+ wire. Further inspection showed the wire was actually broken in half, but still making contact. After calling a few local wreckers to no avail, and contacting a local ford dealer, who after a very lengthy conversation(apparently jumper and extension mean two different things) told me there were no new harnesses in north america. He did provide me with the part number F68Z12A690AA.

So I proceeded back to work(Frieghtliner dealership) to see if I could match any of the pins to rewire the harness I have. To my surprise we had the pins that would work for the MAF connector(Detroit Deisel #AJ/171662-1). So after rewiring the rubbed wire, I cleared the codes and took it for a test drive. No more problem. I will also say that I did change the MAF anyways, and will now put my old one on the shelf should I run into a problem with my new one.

 

Yea, you have to watch those wires. They will separate inside the insulation, -usually at the bend. I haven't had a problem with the MAF wires yet, but both IAT and CHT wires came apart inside the insulation at different times. Couldn't tell it was broke until it didn't pass continuity.

 

Yeah and that is the problem. I found a very slight hole in the wire, and when I peeled back the insulation, I found the wire was separated. Problem was I had already checked the continuity, and it was good. Another stupid thing is, at work, when testing any sort of harness, we'll disconnect both ends, and burn a headlight through the wire. If the wire is bad, it'll burn a hole right through the insulation. Easy find that way, but I didn't even think to use that technique here.

 

I can tell you've troubleshooted these PITA problems before lol. Fun aren't they...

 

Many many times before unfortunately. For craftsmanship I'm sure glad ford builds a relatively good product. Compared to Freightliner trucks(I know I'm comparing apples to oranges), that are manufactured in mexico. I work at a dealer as a tech, and its unbelievable what kind of condition the trucks are straight from factory.