P0171, P0174 but engine runs smooth

[Ranrax]

I recently replaced all of my COP's and plugs, due to a few misses I was having. On my way to work today, I threw the ol' P-0171 and P-0174 (lean both banks). I thoroughly cleaned my throttle body (including exhaust ports), and MAF about a month ago. I have great vacuum and haven't been able to find any vacuum leaks so I don't think I have one, but I am running out of things to check. My engine (5.4) runs good and smooth, no misses, no hesitation, no nothing. It only seems to throw these codes when it gets really cold (-1 deg. today).

It still runs good, so I am not panicking just yet, but does anyone have any other ideas of what else I could check???

Thanks,

 

[hooraah]

You said you don't have any vac leaks, but I would check that rubber PCV elbow at the bare minimum. The last time I had 0174 and 0171 (or I thought it was 0170) thats what it was.

 

[bedrck46]

you may also want to check the DPFE sensor and the hoses going to it

 

[Ranrax]

Thanks, I will double check it. I haven't put a vacuum guage on it, I just can't hear/feel any leaks and it isn't missing, but it is definitely worth a look though.

 

[48dually]

I had the same codes and mine I believe is an exhaust manifold leak

 

[hannibal]

what was your truck running like before you changed the packs and plugs because my running like crap! sputters all the time

 

[Berg]

check those elbows they melt closed

 

[Ranrax]

what was your truck running like before you changed the packs and plugs because my running like crap! sputters all the time

It was missing when under load. I have a code reader and found the problem was with just one cylinder, but decided to change all plugs and COP's because of their age. It is a pretty easy job, #4 and #8 are the hardest to get to, but they aren't as bad as everyone makes them sound. Just take your time and tie-wrap the hoses up and out of your way.

 

[Ranrax]

check those elbows they melt closed

Thanks, I'll check them when it warms up a little..... 9 below today. If they were melted closed I would think it would affect the way it runs, but I will still check them, just in case.

 

[Ranrax]

I had the same codes and mine I believe is an exhaust manifold leak

Thanks, heven't heard of this one before. Was your leak at the motor, or the pipe connection?

 

[48dually]

my leak was at the engine to manifold. the bolts for the manifold have a tendency to rust then snap off. the codes showed up after I heard the puttering of an exhaust leak, replaced manifold gasket and bolts and went away until I heard the other side start to leak. then a little while later the codes showed up. the way I took the code of being lean was the o2 sensor wouldn't get an accurate reading causing it to run lean. could be wrong, and if so im sure someone will straighten me out.

Jamison

 

[cjennjr]

My '98 Expedition showed the 0171 and 0174 codes. The culprit was the PCV hose going to the back of the engine - the elbow hose was completely broken, thereby allowing more air into the system. I purchased a new part from AutoZone ($6.00), took the old part off (its a pain in the ass to get to, but with persistence, you can do it) and put the new one on. I also cleaned my MAF sensor and my K&N air filter, cleared the codes, and now my Expedition runs like new! This is an easy DIY!!

 

[AZ59apacheguy]

I also cleaned my MAF sensor and now my Expedition runs like new! This is an easy DIY!!

What did you use to clean your MAF. I have a K&N Filter and was told those will contaminate a MAF over time. Thanks

 

[BAD RONALD]

What did you use to clean your MAF...

CRC Mass Air Flow Sensor Cleaner, 11 oz. 05110: Advance Auto Parts

 

[AZ59apacheguy]

Great Thanks!!!

 

[richinspirit]

FYI: I had these two codes show up after handling a couple COP-boot leaks throwing missfire codes (around 176k), and at 180k mileage my P171 & P174 were gone after a new battery and alternator went in.

Got a no start condition before dedicating time and money to the lean condition (which I heard causes the engine to try to run rich-as-hell) and replaced a battery, while having these codes and a very low budget. Then had to replace the alternator, starter, and warranty that battery, but then those "lean bank 1 & 2" codes went away and haven't returned in months & thousands of miles. Not sure, but I may need a fuel pump in my future.

That was unusual enough I figured I'd share.

 

[tk421mrg]

After 2 years with p0171 and p0174 on 2002 5.4 4x2

I started out with P0171, then within a week p0174 also, I changed the fuel filter, cleaned the MAF, changes all plugs and a few coils as they failed. I changed the fuel pressure sensor, and adjusted the throttle position sensor. After about two years it still ran ok but couldn't shake the codes. it started then to get worse, couldn't accelerate very fast, would hesitate on turns and almost seemed as it the transmission was slipping horribly, as well as getting only 8mpg. Finally I took it to a shop, for 100$ they told me that the Intake manifold had a leak and wanted 1100 to fix it. I said nope and did it myself saving a lot of money, but still had the codes and still hesitated. Finally I thought it was fuel related, but didn't want to tackle a fuel pump. It ran but just acted like it wasn't getting enough gas. Everyone told me Fuel pump would just not start, not run badly. It only has 117k miles so again everyone told me fuel pump cant be bad... well it was, I finally tackled the fuel pump and after replacing it the codes are gone and it runs beautifully. I believe the fuel pump was failing slowl hence the p0171 and p0174, lean on bank one and two caused by low fuel pressure or low fuel delivery, not too much air. hope this helps someone else with the same issue.

 

[bc11]

I get both codes on my 2000 F150 5.4L PU. Has a broken off bolt on the rear passenger side exhaust manifold. Tried welding onto it to take it out with no luck and give up. It runs fine during the summer but runs rough each winter. Something about the cold makes it worse. Probably won't worry about it unless it gets worse.

 

[luv2shroom]

I know it's been a few years..but both my codes went away when I changed out my o2 sensors...
...was kinda pricy, but well worth it