Check engine light and code p0171

[mike.elmes]

Can anyone shed light on the nature of my check engine light code P0171 Too lean. I have had the TRD S/C installed and at the time of the CEL it was at 1000 rpm idle. The engine runs excellent and idles beautifully. It is very powerful under hard excelleration.The truck is a 2000. I have headers/y pipe and catback exhaust. All of my previous mods were done a while ago and there was no CEL on prior to s/c install.

I am getting the fuel injectors all flow checked and new O rings and upper O rings changed this week. By the nature of the too lean code at idle I guess I'll have to assume that it's not getting enough fuel at idle.Low fuel pressure or maybe a plugged fuel filter? The intake is OEM stock with the Toyota air filter.
The installer is pulling the fuel rails off and pulling all Fuel injectors to replace all the O rings anyway, so he said, we might just have them all flow checked for the 5 buck each it costs.After that, if the CEL comes on again with the same code we'll have to call TRD.The installer is calling TRD today but I just wanted to see if anyone else had run into this.
mike

[dupont24]

The most common cause that we see at the dealer is a MAF sensor, especially if you have a K&N or other oiled air filter. O2 sensors can also trip that code. Fuel filters and other thing rarely trip that code.

[mike.elmes]

I have the stock airbox and OEM filter.I believe its an issue with the s/c...eveything works perfect except that dang light.

Originally Posted by dupont24

The most common cause that we see at the dealer is a MAF sensor, especially if you have a K&N or other oiled air filter. O2 sensors can also trip that code. Fuel filters and other thing rarely trip that code.

[meatmush]

Originally Posted by dupont24

The most common cause that we see at the dealer is a MAF sensor, especially if you have a K&N or other oiled air filter. O2 sensors can also trip that code. Fuel filters and other thing rarely trip that code.

So if the MAF is the problem what can be done about it? I recently installed a oiled filter system and my p0171 tripped. So what do i do now? Engine seems to run fine besides that light.

[TRDTUNDY]

same here on my 07 4.7 and i just got back from the dealer to have that thing reset but it still came up.
is there any aftermarket MAF sensors that would not do a "check engine" light? hehehe
its annoying

[funlver]

This usually works. Try taking the sensor out of the air filter housing. With it disconnected, if you look down the sensor you'll see two tiny little wires. Notice if there is a fuzz built up on it. Try spraying brake cleaner or contact cleaner on the wires. DO NOT TOUCH THEM!!!! Then blow it out and notice if the little wires look a lot cleaner. there is also a little bulb on the side of the sensor thats the air intake sensor clean that too. When done reinstall the sensor and disconnecting the battery to reset the computer.

[djosephm]

From my experience, if you drastically change the air intake system it trips your O2 (oxygen sensor) that plugs into the air intake to tell the computer how much airflow you are getting.

That is why tuners are made for vehicles that people put modifications on... they plug in to the ecm (computer) to the vehicle and "tune" or make changes to the computer so it updates it to your current modifications so your engine will run right.

Essentially the error is coming up because the computer thinks you are running a stock air filter, but really you have upgraded and the sensor is recognizing that.

The other possibility outside of tuning the ECM (computer) of the vehicle is plugging a special O2 sensor in place of the stock O2 sensor to trick the computer so it doesn't bring that stupid error message up.

We desperately need a tuner for the Tundra, but nobody makes one. That is why our trucks will not run right with modifications. Now that this is cleared up.

Back to the topic...

[whateverz]

Mike, does it surge at all? I have the same code, could be a different problem (I don't have a SC) but you can check this other thread for info...
Took My K&N FIPK off and put the stock air box back on...PROBLEMS!!!

K&N's oil is not compatable. I belive any oil would cause a problem.

I have cleaned it with electronic cleaner, and it changes, not eliminates problem.

Let us know about the injector flow. I will probablly try that area next.
Who can flow check them????

BTW....."Tuners" are unable to change any values in closed loop, I belive. So you would have to put in a stand alone computer

[Azgoldrat]

My Corrado G60(factory Supercharged VW ) Started running lean at idle.
The FPR or fuel pressure regulator turned out to be the issue.
I had a 3 Bar FPR and changing to a 4 bar solved the issue.
Older injectors with the nozzles clogged up will also cause a poor spray pattern at idle with a supercharged engine causing Lean Condition.
If your system has a extra injector for over fueling then it is most likely used in the cold start/idle circuit also. Check the connection/harness there too.
Put a gauge on the Fuel rail and watch to see if the pressure drops out at idle.
My G60 was Stage III and put out 16-22 Lbs of Boost. on a 1.8L 20V, made EVO's Look Slow and stole the thunder from the Lightning. That little car was wAAY too much fun.
Hope it helps.
Az

[whateverz]

Originally Posted by Azgoldrat

My Corrado G60(factory Supercharged VW ) Started running lean at idle.
The FPR or fuel pressure regulator turned out to be the issue.
I had a 3 Bar FPR and changing to a 4 bar solved the issue.
Older injectors with the nozzles clogged up will also cause a poor spray pattern at idle with a supercharged engine causing Lean Condition.
If your system has a extra injector for over fueling then it is most likely used in the cold start/idle circuit also. Check the connection/harness there too.
Put a gauge on the Fuel rail and watch to see if the pressure drops out at idle.
My G60 was Stage III and put out 16-22 Lbs of Boost. on a 1.8L 20V, made EVO's Look Slow and stole the thunder from the Lightning. That little car was wAAY too much fun.
Hope it helps.
Az

How would the FPR effect it in closed loop at steady throttle 2-3k?
Wouldn't you see a problem at WOT? Reason being my problem does it only in closed loop, and the FPR is just a mechanical device not related to the computer at all. Right? I guess that would be worth a try, cheap thing to knock off the list. Might be the problem for Mike if it is only at idle that it is leaning out.

[Azgoldrat]

A Faulty FPR will affect lots of different things The computer has no way of knowing the the fuel rail pressure has just dropped out so it will in effect cause a lean condition even at 2-3K. Think about it. If you are driving along and all of a sudden the fuel pressure drops out the injectors do not have the pressure to deliver the correct fuel charge, Engine is sucking air like mad and not enough fuel Ding. Computer see's lean condition and throws code.I am not saying that is your problem but I would look there as a possiablty.(on Edit) Reading your problem in other posts begs me to ask couple of questions 1) Have you done a leak down test on the fuel rail with a pressure gauge yet?? If it drops the gauge after shut down then you have a leaking injector. 2)have you pulled the injector(s)Flow tested???Ultrasonic cleaning??? or the spark plugs and match test the colors??? You have a jet chip right? You have had it Reflashed after changing the airbox back Correct? If you still have bosch plugs get rid of them the 4.7 does NOT like that plug and they will light the CEL I had them given to me and I installed them truck ran great for about 3,000 miles and then splat right on its face Started running like goose turds. Put in NGK's and Hello we are back...
SEA FOAM is a great fuel system cleaner and When used in the Vac line it will clean alot of the intake and Fog for bugs at the same time.



AZ

[whateverz]

Azgoldrat, makes sense. Going to try it, thanks.

Mike, what was the outcome with your injectors?