Code P0171, Stealership report, My attempts and current status, please advise!

[P_Code_Killer]

I posted this on another forum but thought I'd try it here as well.

My background: Total newbie who's learning new tricks everyday as of just a few weeks back.

My story synopsis: I believe my local Toyota dealer(stealer?)ship has tried and partly suceeded in screwing me over, and I'm still trying to figure this thing out after following a few suggestions from Autozone, and from AllDataDIY.

My full story:

I've had a CEL come on and off every couple hundred miles for a while now. Since it would always go off, I figured it was a glitch or something because every time I'd be ready to go in to have it diagnosed, it'd be off again before I got there.

Recently it's been on/off but with less mileage intervals in between. So I'm still thinking it's a glitch because wouldn't it just always stay on if it were not? That's my assumption, so please if I'm wrong tell me why.

Most recently, I decided, hey I'll take this in anyhow on the CEL ON phase because I'm just curious about it now (even though it's been driving fine.) First take it to Autozone to have it scanned and it comes up P0171. Being the newbie that I am, the probable causes list is next to no help to me, but I figure maybe my local Toyota dealership can help me figure this out. (ha ha ha).

I take it in to Toyota. They say diagnosis will cost $110 but they can apply that to any fixes so I agree....They come back an hour later telling me it's a faulty MAF sensor and they can fix it for the low low price of only $441.31. shocking.gif Oh yeah and also apparently "engine has stuck oil rings and timing chain tensioner along with head gasket are leaking oil" because I tell them my car goes through oil quickly. They got to finding that in an hour? Oh yeah that quote is $2671.35. The guy asks, "You like this car, riiiiight?" Not that much buddy. I walk out paying the $110 and basically P.O.'ed/let down. I leave and the light is stuck on for longer than I ever remember it staying on. What DID they do to my car? It now idles weird too?

Thus begins my research. Figure out I can spray the MAF sensor and how to do it and it seems to help the post-Toyota idle. Ok cool. Maybe I'm done. No. P0171 makes it's first return. I decide maybe Toyota is right and I replace this "faulty" MAF sensor with a refurb from Autozone for $90. Fixed? No!

So now did Toyota lie to me or did Autozone just sell me another faulty part? I decide I need some expert advice to find out and purchase ALLDATADIY membership and see that I can test my MAF sensor with ohmmeter/voltmeter which exact process is detailed here:
How to Check Your Air Flow Meter | eHow.com

I was able to do the first part and check the ohms and they check out right. Cool.
I then hook it up to the wire harness and turn on the car to test the voltage. I flip the harness around and see the 5 light brown circle shaped spots with the wires in the middle that are the area where 2 out of those 5 spots are the VG terminal and E2G terminal spots. Now this is where I'm confused because I could only get the (needles?) of the voltmeter to touch the light brown outsides which I'm guessing is incorrect, but if I try to stab in the center where the wires are going in I'm afraid it'll cut into it. I tried pulling in the wire a little as I though maybe I'm supposed to remove the light brown part. Any ideas? If I did this right by just touching the light brown outside and blowing in the MAF then it's faulty. Please advise here.

Other attempts made to rectify this situation:
Sprayed the new "refurb" MAF with cleaner also. OK.
Replaced 4 Spark Plugs per advice at Autozone after Cylinder Misfire on #4 was detected in between my P0171 code checks.
Checked PCV hoses, checked out airbox, air filter, for secureness. OK.
Ran GUMOUT Regane through fuel system.
Ran Lucas Upper Cylinder Lubricant through fuel system (now on 2nd tank run).
Read a Technical Service Bulletin which suggests possible leak at intake manifold may cause this whole deal! What?
Ran Marvel Mystery Oil through crankcase after reading it could help with the stuck rings issue.

Conclusion: I've been "borrowing" my parents garage as my apartment doesn't have one for this. They think I'm nuts because my car is running pretty freakin' great actually since I've ran some of these products through the car. No noticeable driveability issues except here and there hesitation but not always and only when CEL is on. Otherwise it's acting beastly! But the CEL is still ON/OFF, ON/OFF and I'm obsessed now with beating this and not getting ripped off anymore.

Side note: I did the butterfly intake mod over the weekend which I suspect could also put me back at square one with P0171? Correct or not? I'm loving it though. Also, I did plug up the hose when doing said b/f mod and reset everything by pulling EFI fuse to turn CEL off (again).

and finally LOL, the finale: DAMN YOU P0171! DAMN YOU!, but seriously, any help would be greatly appreciated.

[subspec]

lol. ive always had problems with autozone referb parts. id spend the extra and get a new one.

but it does sound like a sensor issue but with doing alittle research and from your car ideling iraticly you might have a EGR problem. just something to look into. and usually if you run any type of cleaner or even mystery oil. its just a false sense of a fix or Miracle fix. but thats my opinion.

[P_Code_Killer]

Thanks for the reply. I'll check into the EGR next. Idle seems much more steady recently. Yesterday idle was 750 after it's warmed up, and I believe it's 1500 cold start. I'm still wondering whether I did that voltage check right on the MAF because if I did it's still under warranty and I need to get a new one. Will try to post pix next of the back of the MAF harness connector I'm trying to test to show how I'm doing this and if that's the right way?

[cbcelica]

yes that tsb will fix p0171 code. the intake manifold leaks which allows unmetered air into the engine causing it to run lean. i would start with this. the manifold gasket is cheaper and not hard to install. Also, i just read the tsb, it also says this problem may result in cylinder misfire codes. It pays us techs 1.6 hours to install. i could do it in half an hour, not difficult only need basic hand tools and knowledge. i say u try it

[Pineapple]

A quick Google for P0171 return: System too Lean (Bank 1).
So check or replace your O2 sensors. Got nothing to do with MAF.

[cbcelica]

A Dirty Maf Can Too Give U P0171.

[P_Code_Killer]

Originally Posted by cbcelica

yes that tsb will fix p0171 code. the intake manifold leaks which allows unmetered air into the engine causing it to run lean. i would start with this. the manifold gasket is cheaper and not hard to install. Also, i just read the tsb, it also says this problem may result in cylinder misfire codes. It pays us techs 1.6 hours to install. i could do it in half an hour, not difficult only need basic hand tools and knowledge. i say u try it

Ha! I'm so new to under the hood, that topping off my oil seemed like a big deal a few weeks back. That said, I'd still like to give this a shot, but with all the draining coolant steps and specific torque specs, I'm without tools to work on it. I was thinking of just tightening up around manifold but need a torque wrench so will check into that next.

As for my MAF testing that I explained in my opening post, here is a pic I took of the back of the MAF harness that I was trying to test with said "light-brown" parts.



Ooh pretty colors! Ha ha. But really...

I highly doubt I was supposed to hold the needle on the brown part, or stab into the holes where the wires go. I tried both though and the needle was basically too big to go very far in the center. Do I need to pull out wires/brown parts how is it done? I tugged on them with a little force but didn't want to damage it so I stopped. Also I know it needs to be connected to the MAF for the test and all the other procedures for the test, but I took the photo with it disconnected to show it better. Any ideas, anyone?

[SSCelica0890]

Originally Posted by Pineapple

A quick Google for P0171 return: System too Lean (Bank 1).
So check or replace your O2 sensors. Got nothing to do with MAF.

Pineapple Is Correct! Same Exact Code And I Checked My O2 Sensors And They Are Burnt Up Like You Wouldnt Believe. My CEL Stays On Though! Universal O2 Sensors Are About $68 A Piece But If You Get The Exact Fitted O2 Sensors You Will Very Well Pay Over $115!

[jons02gts]

Originally Posted by P_Code_Killer

I highly doubt I was supposed to hold the needle on the brown part, or stab into the holes where the wires go. I tried both though and the needle was basically too big to go very far in the center. Do I need to pull out wires/brown parts how is it done?

remove the plug its self, get some safety wire, attatch/ coil it around the lead for the multi meter. once done doing that, you will be able to fit the safety wire into all the female endd of the plug.

[Pineapple]

Originally Posted by SSCelica0890

Pineapple Is Correct! Same Exact Code And I Checked My O2 Sensors And They Are Burnt Up Like You Wouldnt Believe. My CEL Stays On Though! Universal O2 Sensors Are About $68 A Piece But If You Get The Exact Fitted O2 Sensors You Will Very Well Pay Over $115!

Let see how many MAF he went through before he try O2 sensor

[P_Code_Killer]

Originally Posted by jons02gts

remove the plug its self, get some safety wire, attatch/ coil it around the lead for the multi meter. once done doing that, you will be able to fit the safety wire into all the female endd of the plug.

So put the safety wire in the light brown center where the colored wires go? OK will do.

Originally Posted by Pineapple

Let see how many MAF he went through before he try O2 sensor

Haha, 56 and counting! No really just the original one that might've been bad or might not have been that I will never really know. I do plan to look at the O2s but started with the MAF because Toyota said that was it and I was trying to find out if I was being told the truth and also didn't want to pay the crazy fee. I'll never know as this P0171 can be a multitude of things but I will troubleshoot on from easy to hard.

[cbcelica]

well pinneapple how do u suggest he checks the O2? you gotta have a scan tool that'll show u the lean, rich sweeps of the sensor. toyota can do that, im sure they did that when diagnosing the maf.

[Pineapple]

Originally Posted by cbcelica

well pinneapple how do u suggest he checks the O2? you gotta have a scan tool that'll show u the lean, rich sweeps of the sensor. toyota can do that, im sure they did that when diagnosing the maf.

Voltmeter and take it out to check. Same thing with what he's doing on the MAF.

He had replaced MAF already and the problem is still there. Shouldn't he start looking some where else?

[cbcelica]

i would do the tsb dude...

[P_Code_Killer]

Originally Posted by cbcelica

i would do the tsb dude...

Yeah I'll re-torque and see if it fixes the CEL. I haven't had it for about 100 miles but then again, I've done 3 resets. My gut says it will fix with just the re-torque. If not, I'll wait until it gets warmer and go to my bud's house that I just found out has some drive up ramps and have a little maintenance day over there and do full tsb.

[jons02gts]

Originally Posted by P_Code_Killer

So put the safety wire in the light brown center where the colored wires go? OK will do.

no disconnect the plug, look where it connects to the sensor, that is the female end, you will see small holes, the wire goes in there. not the back side of the plug, doing that, you are asking for trouble.

[P_Code_Killer]

Originally Posted by jons02gts

no disconnect the plug, look where it connects to the sensor, that is the female end, you will see small holes, the wire goes in there. not the back side of the plug, doing that, you are asking for trouble.

The official manual says the connector is supposed to be connected to the MAF meter for the test. You blow into the sensor while connected and check for voltage changes by testing the the back of the connector itself at the same time, and with the ignition turned to ON. I believe I just need different, smaller probes to test this. That said, my car is running great and I'm not in any hurry to do this test unless I get more frequent CELs.

How to Check Your Air Flow Meter | eHow.com
In step 5, this unofficial guide shows this connection and is the exact same picture used in the manual itself.

[jons02gts]

if thats the case, than you should just be able to touch the lead to the wires and be fine. if its a good meter, the sheilding should not be a problem measuring the voltage.

[dirtking]

Originally Posted by P_Code_Killer

The official manual says the connector is supposed to be connected to the MAF meter for the test. You blow into the sensor while connected and check for voltage changes by testing the the back of the connector itself at the same time, and with the ignition turned to ON. I believe I just need different, smaller probes to test this. That said, my car is running great and I'm not in any hurry to do this test unless I get more frequent CELs.

How to Check Your Air Flow Meter | eHow.com
In step 5, this unofficial guide shows this connection and is the exact same picture used in the manual itself.

In reference to testing wires and circuits what I have done many times without any problems is to take a SMALL straightened paper clip and slide it in the back of the socket where the wire molds into the plug. You should have a soft rubber donut molded around each wire entering the back of the plug. Just slide the small paper clip in until it bottoms out where the rubber donut contacts the wire. CARFUL as the bare paper clip could be live (voltage) so make sure it doesn't touch anything else (ground, another exposed wires etc.). Now you have access to the wires voltage, resistance, feedback or what ever you are trying to measure.

In reference to replacement parts (MAF, OXYGEN sensors, Cat converter, etc.) this is what my bro in law told me (he works for Toyota in the service dept): Toyota products are very finely tuned thus making them finicky to aftermarket replacement parts (especially sensors) that are manufactured by other companies. I know its more $$ for the OEM Toyota part but keep what was just stated in mind. I have always gone with Toyota parts especially when it comes to engine management issues (sensors, Cat converter, etc.) and I have, so far, never had a problem with any Toyota part I have had to change. Just my opinion,, hope it helps.

Mook.

P.S.
In my experience a lean bank code commonly stems from the following issues, but not necessarily in this order:
1) Fuel system not delivering enough fuel causing a lean condition. Check: Fuel filter, fuel pump, fuel press regulator (all of which are located in the fuel tank accessed through service port in the floor under the rear seat) and don't forget about your fuel injectors possibly being clogged which normally would be the least of these common causes, but you never know.
2) Vacuum leak(s) allowing more air into the system that the Mass Air Flow sensor does not know about causing the computer engine management system to inject an amount of fuel needed for (hypothetically) 10 cubic feet per minute of air flow while driving when in reality the engine is taking in more cubic feet per minute of air flow due to vacuum leak(s) causing a lean condition. Check: All vacuum lines, intake air box connections, intake manifold gasket, etc.
3) Last but NOT least. Faulty sensors causing the computer engine management system to manage the fuel delivery system incorrectly causing either a lean or rich condition. Check: Operation of MAF sensor, Oxygen sensor (pre cat converter oxygen sensor, not post cat converter oxygen sensor) Fuel pressure sensor (also often called "fuel vapor pressure sensor"). I have a competent mechanic with a quality OBDII scanner. NOTE: A basic lesser quality OBDII scanner will basically only give you basic trouble codes. The more expensive ones can actually read sensor operation by being able to read sensor voltages, resistances and feedback. Compare these test results with the tolerances in your repair manual and you can often find the sensor or system at fault. I just throw him a few $$ to monitor the sensors with his OBDII tester and so far it's been a very effective troubling shooting technique.

DAMN,,, does this guy ever shut up? LAMO Good luck,, it can be frustrating but with experience it gets a lot easier.

[P_Code_Killer]

dirtking,
I've been researching the MAF harness (plug) test and have realized the same thing you just told me. I can use sewing pins/paper clips hooked up with alligator clips, or get an actual "back probe" kit and hook it up. CEL is still out, although just did another reset so LT FT is yet to be determined; short term doesn't seem to be an issue I'd guess cause 55 miles without CEL. I took my butterfly out again, and ripped out more stuff today just for a 1/2 trial run of sorts to see how I'd do trying to install a SRI/CAI, plus I pushed one of those pop rivet things in the center and the center fell inside the freakin' car so I removed upper and 98% of the lower airbox (totally off except for one electrical snapped/locked on somehow; not the plug) to find it and it never turned up; it's probably in the front bumper. Damn. Anyhow...yeah I digressed and I'm cool with long posts.

About Toyota parts, I just read an article today about the Universal O2 vs. OEM so what you said re-affirms that point. Don't buy the Universal because the computer doesn't like it. I'd have to agree that if my O2 is the culprit, I'll be getting OEM for that. I think the MAF I bought from Autozone was OEM but just refurb.

I have become well acquainted with the possible and probable causes of the LEAN running condition. I'm hoping it was just clogged injectors; the Lucas really seemed to help, I'm on my 3rd treatment. As far as the fuel filter, I thought about that too, but am not sure of my ability to work on it; esp. IN the fuel tank? Thanks for tip about checking pre-cat instead of post-cat O2.

Another thought about my air box. I noticed the 3rd clip (the pain in the ass one closest to the headlight) wasn't secured so I re-secured it. I picked that up from an article also; another guy had P0171 and noticed his quick lube place didn't do it; and guess what, I use quick lube places too. Well I know how to change an air filter now, LOL go me. Now I see why that's such a joke to most people who work on their cars; although it is a bit of a chore more than it needs to be on the Celica anyhow.

I'm gonna borrow a torque wrench from AZ and check up on the intake manifold and also get some diagnostics done. I have a lot of info on this; but I've been mid-way distracted by the thought of CAIs. I'm just a bit obsessed now. LOL.