P0171 Causes?
 

I just got back from a little road trip out to Greensboro to see Bob Seger.. Been a fan since Christ was a corporal..

I was hoping to see what the ol' girl would get on the highway- I was hoping for around 15MPG- and I was all over it until PFFPFFPFFPFF- I thought it was another lifter collapsed, but it is either an exhaust leak or a vacuum leak..

the result is a P0171 Bank One too lean code..

looks like the culprits are often: vacuum leaks, stuck PCV, bad MAP sensor, Bad o2 sensor, clogged cat, weak fuel pump/clogged fuel filter..

It acts like a clogged cat.. or- I should say a 'clogging' cat that hasn't all the way choked up yet.. I run it above 2300RPM and it runs fine.. below that and after it closes loop it runs like CRAP- and just like it would run if the cat was clogged.. It PFF PFF PFF's down the road as if there is in fact an exhaust leak- or it could be a really pronounced vacuum leak too I guess.

So- would a leaking header manifold be able to create that code? AND- would a leaking header manifold be possibly rooted in a clogging catalytic converter? Have I missed anything else that could be causing this?

I'm about to go out and start looking it over- any help would be appreciated!

edited to add: it runs fine above 2300RPM so long as there is no load on the engine.. if I pop the throttle it bogs.. and it struggles to get to that range to begin with.

do you have highflw cats yet ?

yup.. one on each bank (true duel to magnaflow true x muffler)... they are magna flow high flows.

Disconnect he O2 sensor, take it for a drive. Run better? Replace the O2 sensor.

its the O2 reporting that the exhaust is lean, in spite of all the pcm's efforts to richen it.

it "might" be an exhaust leaking allow the true exhaust to escape.... but i doubt it.
its more likely a vac leak on the intake side.
any easy way to check that, is to temporarily disconnect and cap off all vac ports, and see if it fixes it. than add them back one at a time to find the culprit.

several months back I was sitting bored on a Saturday afternoon and decided to 'pop' those shorty headers on the truck that had been collecting dust... about 18 hours later I had them on.. the bends on the middle ports are almost impossible to get at to tighten..

every week or so I would break out the 10mm wrench and tighten them down..

i had become complacent in this little activity of mine- and just got burned..

the center two ports are held by only two bolts.. the forward one is super easy to get to and tighten- especially if you remove the wheel shroud.. which I did.. the other one (closer to the back) is all but impossible to get to..

it was barely in there at all.. if it weren't for the fact that it's impossible for it to fall out, it would have. I just burned the crap out of myself and tore the hell out of my knuckles getting to it, and painstakingly, and in maybe 1/32 increments, tightened it back up.. well, as good as I could until I rounded the bolt..

that bad bear was leaking like no tomorrow.. badly.. very badly..


I didn't find any vacuum leaks, but you know how those things are- I'll be on the lookout for them..

I'm going to go ahead and guess teh leak is what caused my issue- the leak not screwing with performance all by itself, but the leak tripping the o2 sensor out and IT screwing with performance.. It was dumping fuel like it was cool.. I could dang near watch the gas hand move..

I cleared the code w/ the SCT, and noticed immediate return of performance.. I'm still leaking- so that is on the to-do list.. the problem w/ these headers is that you have to put the screws in the holes before you align it on the head... there is not enough room to pull the bolt out and replace it.. I'd like to get my hands on my former self who looked at the design of those things before I bought them and said it was okay- i'd strangle me if I could!

There are some sort of bolts designed for your application that lock completely and don't allow for vibration loosening like you're experiencing... don't get me lyin on where to find them though.... If I can find the site where I saw the aforementioned product, I'll post a link; maybe they'll do away with your header loosening problem.

As for the bolt you rounded off... I have, in my frequent fits of rage, done the same many times... best way I've found to remove the offending bolt is to get a socket 1 size smaller and beat it on there with a sledge hammer, then carefully and slowly back the bolt out.

Stage 8 locking header bolts.

Didn't you know? These are LUXURY trucks. Power brakes. Power steering. Sweep Second hand on the gas gauge......

you'd probably have to do it in 1/32 inch increments. LOL.

**** headers!