who here knows how to interpret freeze-frame data when diagnosing DTC?

I'm at my wits' end with this stupid MIL. p0171 'system too lean' I've got the freeze frame data from my cheapo scanner but I have no idea how to interpret those numbers to help me narrow down the possible causes. ( the list of potential triggers for p0171 goes on seemingly forever.) Car has been down 5 months (blown HG.....now rectified, along with lots of extras). I'm out of time, out of money and my patience went MIA sometime last year.
Throwing myself on the mercy of the TW technical wizards 'cuz they're the best on the 'net.
(seriously. the only other guys who even come close are some of the various Honda tech wizards-but TW sets the bar).
I'll type in (yeah I know, cheapo scanner, remember?) the three pages of numbers from the freeze frame if someone is feeling helpful....
Thanks for reading.
Edited for clarity: What I'm looking to do here is give the freeze frame data to someone that can translate it into a 'short list' of most likely triggers based on that data. Point me in the most likely direction for the culprit because otherwise I'ma die of old age before I complete the troubleshooting list.

 

You mention head gasket work and 'lots of extras'.

You don't tell us what you've done (if anything) in chasing this code, or how the truck is running otherwise.

I'd start with this generic list of potential sources and evaluate which of those you touched when the motor was torn down.

Odds are that there is a simple reassembly error.

P0171 Causes
The P0171 tells us that there is a lean air-fuel mixture, but it doesn’t tell us what could cause a lean fuel mixture. There are actually many different things that can cause a lean mixture. The following issues can be caused by the P0171 code:

• Air intake/vacuum/boost pipe leak (Most common)
• Faulty PCV Valve
• Low fuel pressure (Caused by a bad fuel pump, filter, or fuel pressure regulator)
• A faulty EVAP purge valve
• Faulty O2 sensors
• Faulty EGR valve
• Faulty MAP/MAF sensors
• Exhaust leak (Before Front O2 sensors)
• Coolant temperature sensor
• Faulty sensor wirings
• Faulty ECM/PCM (Rare)

 

Post your freeze frame so we can see it, it is also wise to double check your work in the area last worked on when you for say do engine work then following that get an engine issue.

 

First off was the problem (P0171) present prior to the headgasket repair?
What parts have been fired at this problem?

Live data is much more useful than freeze frame unless diagnosing an intermittent issue but if freeze frame is all you have at the moment some key PIDs I would want to look at are:

RPM
Vehicle Speed
Engine Load
Throttle Position
Mass Airflow
Coolant Temp
Short Term Fuel Trim
Long Term Fuel Trim
Upstream & Downstream O2 Sensor Voltages

 

I know I should get directly to the subject of this thread and answer the questions but I feel like it's just as important to first say THANK YOU to @Clearwater Bill, joba27n, and Dm93 for taking the time so far-feels like I've been thrown a lifeline while drowning.
@Clearwater Bill: yes, new head gaskets. Cylinder heads tanked, skimmed and passed inspection at the best machine shop around, Parrish Automotive in Sacramento. New valve stem seals because I had 'em and it seemed foolish not to use them while heads out and accessible. ' Extras' include new accessory drive belt/tensioner/idler pulleys. Water pump, thermostat (tested before install-easy lesson learned the hard way). Oil pump drive seal (not certain accurate terminology there, sorry). One thing I don't see on your abbreviated list is fuel injector(s)-and it was necessary to replace one with (winces) a used, untested junkyard part.

Edit: I'm not done with this post but screwed up and posted before complete: am still composing reply, which will appear as a separate thread entry (or entries).

 

(continued from #5)
@Clearwater Bill : As far as chasing this code: (typed with a bigger more painful wince): probably not as much as I should, in part because so very many possibilities! I have subscriptions to both Mitchell and Alldata. Last night, immediately after posting this thread, I went back to Mitchell and re-read everything pertaining to the OBD system, starting at Engine Controls. (oh boy, there's a good-size chunk...) Buried somewhere in one of the Diagnostic menus something relevant jumped out at me so I came back here to edit my opening post-and fell asleep while typing. Woke up when laptop started heading for the floor-rescued mid-fall thanks to lucky reflexes! But I digress, (again, sorry!)
Here's what I found while @Mitchell re: troubleshooting this DTC, paraphrased: '...fuel level over 10%' Whoa, missed that the first time. And -fail. Tank now near 'E', which seems could invalidate some scanner data, will correct that as soon as I'm done w/these replies (!), then re-scan, etc.
To finish answering your questions, PCV system good (after finding bad fresh air hose and replacing). EGR sys good (now)+ and no exhaust leaks (now)-
And -cut-I'm going to finish replying to you guys, fuel truck up and re-start properly. With the idea that if I dot all my i's and cross t's I won't waste your time or mine.
@joba27n and @Dm93 : gonna reply to you in next post

 

@joba27n :re: freeze frame results: My apologies. (cringing) I screwed the pooch by failing to follow proper procedure in Diagnostics (according to Mitchell) so gonna go back to 'square one' and try to start from scratch- properly. Again with the intention of not wasting more of your time or mine. I'll post when I got 'em and will understand if you choose not to respond. Meanwhile, thanks for your time, man.

@Dm93 : No, that particular problem (p0171) was not present prior to the headgasket repair. 'Parts fired' (lol): new hg's and all related gaskets and seals. Including (as noted in reply to Clearwater Bill) one used, untested fuel injector nozzle (a potentially problematic choice but the only one viable under the circumstances). I'll quote myself to save some time and maybe make you less inclined to beat me over the head, figuratively speaking: " My apologies. (cringing) I screwed the pooch by failing to follow proper procedure in Diagnostics (according to Mitchell) so gonna go back to 'square one' and try to start from scratch- properly. Again with the intention of not wasting more of your time or mine. I'll post when I got 'em and will understand if you choose not to respond. Meanwhile, thanks for your time, man."

 

Hi all,
First off i apologize and dont want to hijack Ivs2rock's thread but since we have the same issue i might be able to help out with his problem as well as getting help myself. if i am intruding please let me know and i'll start my own.
i just recently replaced my broken timing belt about a week ago(see my thread below) driving it after, all seemed well. but the other day i noticed it to be sluggish on acceleration and when i punched the accelerator (on purpose cause things didnt seem right) it basically bogged down and only moderate accel seemed to work. then yesterday coming back from work i accelerated on the on ramped to the highway and basically the trucks RPM started surging and was struggling and i think i heard a backfire. once i got on the highway, let up off the pedal and only applied light to moderate accel, i was able to make it home(5miles). it noticed that the CEL light came on and when i got home and checked with my scanner it pooped for p0171 system too lean (bank 1)... and also P0450.... EVAP EMMISSION.
this has been the 2nd time i replaced the belt and here are some issues that i ran across:
The connecter plugs clips on the female plug(wiring harness side), to make them securely snap onto the male component ends broke off on the 1/3/5 injectors, MAF SENSOR. I tried to make sure they are at least snug and making contact. The injectors just broke this last time but the MAF has been broke off for a while. i guess its just that darn age and heat that makes them break.
At idle the truck runs perfect, so i dont think it has anything to do with my timing belt being replaced. when i get home today i will take a closer look at those broken connectors again to see if they might have worked their way loose and also to :

@ Clearwater Bill ,

• Air intake/vacuum/boost pipe leak (Most common).........................................................we're talking about the hose coming from the booster to intake right?
• Faulty PCV Valve....................................................................................................... should be good but i'll check the hose
• Low fuel pressure (Caused by a bad fuel pump, filter, orfuel pressure regulator)....... will check others probable issues first
• A faulty EVAP purge valve.................. this is the valve behind the intake with the short vaccum line (approx. 4" L by 1/8" ID)?
• Faulty O2 sensors.... i think i changed it out 50-75K ago
• Faulty EGR valve...
• Faulty MAP/MAF sensors...........................................I'll check connections
• Exhaust leak(Before Front O2 sensors)
• Coolant temperature sensor.... i'll check connection
• Faulty sensor wirings
• Faulty ECM/PCM (Rare)

@Dm93

My TPS has always been a problem, every time i disconnect the battery for some reason and then upon starting, the trucks RPM surges wildly up and down and it wont seem to adjust via the ECM. the only way to correct the RPM's is to go in there and loosen the 2 phillip head screws and adjust the it. right before the on ramp incident i stopped at the post office, coming out of the post office i opened the hood and adjusted the TPS a little. this is usually common as i have to fine tune the RPMs a day or few days after disconnecting my battery. but this time it was a little weird cause it was a week past me getting back on the road. basically i have to adjust it to around 750-800 rpm in PARK before i can get a good smooth idle @ a STOP in DRIVE, then its around 700 rpms



well, this is my story and when i get home i'll go through Clearwater Bill's trouble shooting just to make sure. any more comments /opinions are greatly appreciated.....thanks!

https://www.tacomaworld.com/threads...e-cam-sprocket-question.809861/#post-29067089

 

okay here's the freeze frame data (as listed)

DTC p0171
Fuel Sys 1 CL
Fuel Sys 2 --
LOAD PCT (%) 20.8
ECT *F 136.4
SHRT FT1% 6.2
LONG FT1% 18.0
MAP psi 875
VSS (mph) 0
SPARK adv 14.5
IAT (*F) 104.0
MAF (lbs) .014
TP (%) 3.5
EGR PTC % 0
EGR ERROR 0
EVAP % 0.0
FL1 % 32.2
WARM UPS 0
CLR DIST (miles) 0
EVAP VP (inH20) .12
BARO (psi) 14.5
CATEMP 11(*F) 799.7
VPWR (V) 13.570
LOAD ABS % 16.5
EO__RAT 1.004
TP__R % 0
AAT (*F) 104.0
TP__B % 3.5
APP__D % 0
APP__E% 0
TAC__PCT % 3.5That


Truck seems to be running ok (excluding the high idle becausse it thinks its too lean). Smooth, no misses, nothing really of note.

 

@toyinhawaii : hell no I don't have a problem with your jumping in = I don't consider it hijacking unless you go completely off-topic or decide to snipe at someone's post. And that's not what I see here. Join the party The more the merrier-or at least, the more help we get the more likely we are to (collectively) find some solutions, yes?
BUT. er, on the other hand, a fresh new post topic could possibly draw eyes that have already seen mine and mentally skipped to the next/unread thread.
Your cal..

 

thanks! i guess i'll join the party for now. if i cant get it solved this weekend, i might go ahead and create a new thread monday

 

Hey, not ignoring you just busy trying to find a place to live and such. Admittedly i've skimmed through above because I wanted to get back to you. The fact it's idling high kinda points me towards a vacuum leak. A course way to check would be the hit the engine bay with a garden hose all over while it's running and if it stumbles a little then you know to start looking for a vacuum leak. Another area I would check is to remove the purge valve line if possible and plug it off. And see if that changes things. Kinda confusing reading the freeze frame for that pid but it a potential vacuum leak is the purge valve being stuck open and constantly drawing from there. Usually I find that makes it rich but I have seen it come across as lean to a scanner

 

Srry for not getting back to you sooner, been really busy and haven't had much time or brainpower left to read through things and reply.
If the code started after the repair I'd be inclined to suspect a vacuum leak or something wasn't connected properly. I don't think the one used injector caused it, typically one bad or restricted injector will cause a single cylinder misfire.

Freeze frame while not very helpful and the high idle also appears to point to a vacuum leak, the easiest way to find a leak is with a smoke machine although typically those are beyond the DIY budget. Sometimes they can be found by spraying carb cleaner around things while listening for an idle change and/or watching short term fuel trim, water can also be used sometimes by poking a hole in the cap of a bottle and spraying it around while listening for it being sucked in through the leak.

https://www.youtube.com/watch?v=0rQn9YBMZIg&t=59s

It looks like it's in fuel control so it's not a very big leak if it is a leak.
If you can see live data I would want to see fuel trims at idle and under various driving conditions (typically a vacuum leak will have highest fuel trims at idle).

I glanced through your thread, are you still getting the lean code?
If you are I'd suspect the idle problem is related as disconnecting the battery clears any learned values including fuel trims and idle parameters.

 

Ok, so after i got home friday and got into the driveway under its own power, saturday( yesterday) i changed the short U Evap hose under the hood at the green relief valve, it seemed a little dried up and also the HOSE between the PVC valve and throttle body.. it was hard as a rock. Tired to start the engine and it wouldnt start! Damest thing ! I cranked an cranked but nothing… so i disconnected the high pressure fuel line and cranked it a few times….. nothing! No fuel shooting through. I cant believe it has something to do with my timing belt change… unless something disconnected,etc. prevents the fuel pump from turning on or it is as simple as… maybe the fuel pump crapped out? That would be some timing right there for that to happen. What do u guys think? Oh, the Ign. , efi fuses are good. Is there a fuel pump fuse? Or some other designated fuse i may have over looked?

 

So... how are the trucks