PO171 Lean Bank issue part 2

So after ordering a new MAF Sensor because I was misfiring and stalling out on start up and even idling in drive, same issue.

I was like a kid on Christmas day receiving my sensor in the mail today.

Installed new sensor and seemed ok at first, drove 5 miles to autozone and when I started her
up again, check engine light came back on, she misfired and idled rough again ? ugh.

So, could it be vacuum leak? fuel pump? O2 sensor.... thanks for the help.

Stan

 

02 sensor is not likely, typically you will get a/f sensor code followed by a lean code.
Best bets are going to be a vacuum leak or fuel issue. First get a hold of a code reader with some diagnostic functions. You will want to watch the long and short term fuel trims, your's by the sound of it will be over 10%. Engines produce vacuum at idle but very little at higher RPM. So while the vehicle is running watch these values and then rev and hold the engine at a higher RPM 3000-4000k. If your short term fuel trim changes and becomes closer to 0 at a higher rpm it indicated a vacuum leak. However is the long term fuel trim is off say -10% to +10% this would mean that there has been a change in the engine performance over a longer period of time and is possible that the fuel pump has become weak causing the ECM to try to compensate for a fuel issue.

 

thank you, Stefan. Will check out.

Bought the truck 2 weeks ago for $6900.00 and 148,000 miles. Nice looking truck, just some hiccups.

 

Well, she fired up great this morning and no issues for a while. Real smooth running engine and idling for about 15 miles.

Until the engine got real hot. Turned off truck and waited about 5 minutes and she was misfiring again, ugh.

Replaced the Fuel filter and MAF sensor and ran a test and it's now saying it's the 02 sensor...one is reading and the other one is reading zero.

Called Advanced Auto Parts and they wanted $149.00 ? for the 13104 Oxygen sensor upstream & down stream T100.

So I found one on Amazon for $30.00 and included 2 day ship.


Seems she runs fine when engine is cold for a while, but as soon as the engine gets real hot at optimum temperature she starts to sputter.


Hoping this 02 sensor helps on Tuesday.

Stan

 

So let her sit for 3 hours today, from 2pm - 5pm and then cranked her up to go for a spin to the store. 5 miles round trip and she sounded awesome.

So strange....ugh. Ordered the " O2 sensor 1 " anyway and replaced the fuel filter today.

 

Sooo, if my Long Term Fuel Trim was at 19+, is that a good indicator of a bad fuel pump? Would a bad fuel pump throw it's own code?

I'm chasing down a P0171 code. Trying to make sense of all the data from this new code reader. Short Term Fuel Trim is all over the place, gets as high as 14+, and doesn't necessarily trend towards 0 when increasing RPM. O2 S2 voltage between .1 and .75 (never seen it go to .9) and O2 S1 stays at 3.2. Both close to normal from what I've researched. Any clues? For all the great info on here, this is really hard to pin down.

 

From thoes reading you should be looking for a vacuum leak, check all the rubber hoses for cracks or not being connected. you can try spraying from brake cleaner around the hoses, or intake manifold area and if you hear the idle surge or sputter then you know the leak is in that area.

 

So now I have replaced the MAF sensor, and both the 02 sensors, downstream and upstream. Did a tune up, change spark plugs and replaced fuel filter.

And still get that darn PO171 lean bank engine light code comes on ? Ugh....so over this.

I disconnected battery for 5 minutes, and engine light goes off, but after driving around for about 10 minutes engine light comes back on. Ugh... So frustrating.

Should I disconnect negative battery for 30 minutes? could that help ?


Don't know what to do at this point. Maybe Vacuum leak ? hoses ?

 

like i said before it sounds like a vacuum leak

 

Thank you, Stefan,

Guess will go get some brake fluid and start spraying around some hoses to see if the idle increases or decreases ? yes ?

 

So just for a quote, I take my Tacoma to a auto mechanic across the street from where I work and he tells me $100 an hour to , up to 2 hours to diagnose my truck for

the P0 171 lean bank code and if it's a vacuum leak or an exhaust leak it could be up to $200 to fix and labor, so around $400 out the door.


ROFLMAO, I don't think so

 

ok, so take to a local auto mechanic that diagnosed for free and he is telling me it's a 02 sensor lean bank issue and says only dealer can fix and it's a computer issue ?

what the heck !!

 

have you replaced the fuel pump? which is probably in the gas tank. It being bad, thus low fuel pressure can cause the code. No need to ask me how I know...

 

No, I didn't replace fuel pump, just fuel filter.

 

So after spending 6 hours at Toyota dealership service department.

3 tech, manager they tell me I have the wrong spark plugs in there. So $229 later I walk out.


While walking out, I told the tech that engine light is still on and he said , no worries he will clear it.


Stopped of top fill the tank and before getting on Interstate, check engine light goes back on !


Stopped off a Advanced Auto parts and now P 1133 Air / Fuel Sensor Circuit Slow Response 1 Sensor


I'm beyond pissed and frustrated.


Got home, and truck sat for a few minutes and started and truck misfired and when I pushed on gas pedal she sounded like she was farting outside the tail pipe ?

Slow start, and some smoke came out.


Then turned off, and she turned over right away the next 3 tries. Check engine light still on, from code P0 171 now P 1133

 

First take it back to the toyota dealer and talk to the manager that was a misdiagnosis and demand them to refund you the money.
First i know you replaced the a/f and or o2 sensors, what brand did you use? Denso is the only brand that should be used on a Toyota if u used any other brand u can basically guarantee it to cause a check engine light.
The lean code and the p1133 do not sound to be related to each other, because and issue with the 02 will not cause the motor to misfire like that.
Your main issue is fixing the lean code and go from there, if the engine is not running right it can cause the sensors to not work properly because the engine mechanically is not right so how can they read the values correctly when the engine's exhaust is not performing as it should.

 

So after spending 6 hours on Saturday at the Toyota dealer service department and spending $229 a new spark plugs and tune up because the tech swore that was the issue and had wrong spark plugs in. So when I walked out to get the truck after he drove it around the building, I came up to him and he didn't expect me to soon as I was to wait in lobby, I said , Hey the check engine light is still on ? And he said oh ! don't worry about it I will clear it for you.

So I took the truck and drove 3 miles and check engine light comes back on !! P0 171 and P 1133 codes....Darn it !



So first thing the morning I go back down there at 8:45 am and wait in line without an app. They take me and say you back so soon ? yea right.

I go to breakfast and come back around 1:00 pm and the truck is still in the bay.

Tech tells me it's a process of elimination and now these 2 things need to be fixed before we go any further ?

1. ) Timing Belt Package which includes water pump, CAM and Crank Seals and drive belts. $950.00 plus tax

2. ) Need a Fuel Pressure Regulator with intake gaskets. $582.00 plus tax and $150.00 for the Fuel Injection Service


WTF ?


So I asked him will this solve my lean code issue and get better gas mileage and engine light off ?

He said it should but to be honest, no guarantees because it's a process of elimination. WTF ?

I asked him about a bad " Fuel Pump " and he said first the 2 above issues have to be addressed before he can check fuel pump.

WTF ?


Also said the Side bank is off by a tooth and it is the bank that the cam sensor reads off of. means the cylinders will not fire at those two problems before moving forward.

Tested fuel pressure and idled fine, but under heavy acceleration it dropped to about 20 psi and stayed until I let off the throttle.. Fuel pressure regulator is bad.




I'm just lost for words and very frustrated. Any ideas ?

I did NOT use Denso brand for the O2 sensors. Bought a brand called Abigail O2 sensors.


Stan

 

it sounds like they are unsure of how to fix the issue, first you should check timing yourself to verify that the timing is actually off 1 tooth, its fairly easy just remove the camshaft cover or actually unbolt it and pull it twards the radiator a little so you can see the timing marks on the camshaft gears and set the crank shaft to the 0 degree mark. the simply check that each mark located in the picture below lines up with the marks on the metal backing plate.

There is no reason to start replacing the cam/crank seals and water pump especially if there is nothing front with them, you are simply trying to fix a lean issue.
First verify the timing for yourself because that dealership clearly does not know how to diagnose an issue like this.

 

Thanks Stefan,

Toyota dealership did spend 5 hours today in their defense diagnosing. No charge.

I'm leaning toward replacing the " Fuel Pressure Regulator " first and then go from there to the timing issue and set the crank shaft to the O degree mark.

Keep your fingers crossed and will report back this week.


Stan

 

Bro, slow down with firing off parts at the truck - Like @stefanlg55 said, check for a vacuum leak. Checking the timing is easy like he said as well - check the diagram from the FSM he gave you and if you still need more help watch this around 13 min - it's checking it after putting a new timing belt on, but it'll give you the process in real time:



Also, don't waste your time with the dealership - they don't make money on diagnosis so they don't keep techs with diagnosis skills around at all of them - once in awhile you could get lucky, but it's not the rule by any stretch of the imagination. They make way more money on brake jobs. If you want to see how a real tech works out diagnosis check out Eric O at South Main Auto on youtube. He's the real deal. I'm not saying this is going to be your diagnosis, but this is what a real tech will do to figure out what the problem is before throwing parts at it.



The money you save from not going to the dealership can be spent on high quality denso / oem parts...