Hi fellas,
Those of you who followed my postings, I recently changed 2 knock sensors and their harness, due to a code I had and then engine light coming on.

Now that I fixed that, I have a new code of course I got a new code

The code is P0171, System too lean from ECU 10.

I have tried cleaning my MAF sensor, but no good. I cleaned the whole intake areas when I had to change the knock sensors.

How do I solve this? Maybe faulty MAF?

I am reading O2 sensors, and the OBD2 says they are within specs.


Here is a video of what happens when I press on the gas.
It feels like it's about to drown and then lag for a sec and then strike with power. If I put my foot wide open throttle, the car stutters and goes nowhere, until I release the pedal a little bit then it fires!

* By the way, when I fill up the gas tank, the gas gauge climbs very very slowly. It almost takes 2 minutes for it to read accordingly and raise to the FULL mark.
Maybe it's a fuel pump problem?

 

So many things can cause this do you have a scanner capable of viewing live data? MAF might be faulty, vacuum leaks (hoses, PCV valve) bad O2 sensor, flaky injector...

 

Yes, my OBD2 has a live scanner for the MAF data. What should I look for in that graph?

Checked hoses.
New PCV Valve.
Wouldn't a bad O2 sensor show it's own unique trouble code?

Regarding injectors, they looked fine when I inspected them while reaching for the knock sensors. Although 1 injector had a missing o ring. But doubt it might be the issue.

The car is really struggling to put down power.

 

Is the timing belt replacement past due, ie the knock sensors are picking up the loose timing belt slapping against the belt cover? Is the oil fresh, and the variable valve timing filters clear? Does it have a failing coil? Did the intake get a cleaning on the inside at the passenger side "ACIS" valve, and PCV valve?

 

I don't think the belt is loose and slapping on the cover, the car just feels like it's drowning of too much gas. I was thinking the fuel pump might be bad. How's the DIY for the fuel pump?

Fresh oil.

I am not sure if the car has Variable Valve Timing, but if it does, where is the filter located so that I can give it a check?

I don't know about the coils and how to diagnose them, put in a fresh set of new spark plugs.

Yup, all the intake plumbing was cleaned from all the carbon build up.

 

Missing injector O-ring? Yea I'd say that can cause problems. On your scanner you need to look at the fuel trims I suggest watching a few Youtube vids on that.

 

Hi King! P0171 indicates the three cylinders closest to the firewall are having the lean condition, so your focus should be specifically targeting components that affect this bank of cylinders. Too lean means not enough fuel, or too much air. If you look at the short term and long term fuel trim for bank 2 "radiator side" and all looks good, ie + 2.3% short term, and + 4.6% long term fuel trim "stft numbers should be close to +0%, but on the positive side, ltft # should be closer to +4.5%", then stay focused on the bank one firewall side as the only problem area. The MAF, MAP, TPS sensors, fuel pump, etc are ruled out as they affect both banks equally. If the rough running started after the work was done on the knock sensors, and plugs then you should double check the work already done.

 

Wow moon phase, that is some very juicy information! Thank you.
I'll take this data and compare it to what my OBD2 reads on the car.

And yes, the missing o-ring on one of the injectors is on one of the 3 injectors closest to the firewall.

Is it a good idea to just get o rings? Or are the injectors due as a consumed part already by 255,000 miles?


The car was already stuttering and not moving when the gas pedal was floored, BEFORE all the maintenance I did on it.

Anyone care to chime in as in may the problem be from the air fuel ratio sensor?

 

UPDATE:
I went to the Lexus website that shows precious dealer history, since this is fairly a new car to me, and I found some interesting notes left.


Dealer Reported 06/26/2009

SFI.MFI GUEST STATES THE CK ENGINE LIGHT IS ON AND CAR WAS RUNNING ROUGH. ALSO THE TRAC OFF LIGHT IS ON - INSPECTED AND FOUND CHECK ENGINE ENGINE LIGHT ON ENGINE RUNNING FINE. HOOKED UP SCAN TOOL AND CHECKED FOR CODES. CODE P1354 PRESENT FOR VVT - I MALF. BANK 2 - CLEARED CODE AND ROAD TESTED VEHICLE MANY MILES. COULD NOT DUPLICATE CONCERN AT THIS TIME. RECOMMEND GUEST MONITOR.



Dealer Reported 07/01/2009

SFI.MFI GUEST STATES THE CHECK ENGINE LIGHT IS ON AND THE ENGINE FEELS LIKE IT IS CUTTING OUT EVERY SIX TO SEVEN SECONDS - INSPECTED AND FOUND CODES P1354 P0300 P0302 P0304 AND P0306 PRESENT. - ROAD TESTED VEHICLE SEVERAL MILES. COULD NOT DUPLICATE CONCERN. HAD SERVICE CONSULTANT DRIVE VEHICLE HOME AND WAS ABLE TO DUPLICATE CONCERN. POSSIBLE BANK 2 OIL CONTROL VALVE FOR VVT - I. REMOVED AND REPLACED OIL CONTROL VALVE BANK 2. HAD SERVICE CONSULTANT


Interesting enough, these messages showed up around the 200,000 mile mark.

I know the VVT-i sensor symptoms are close to what I am experiencing. But the engine code is just P0171, just lean system, it's not saying anything about the VVT-i sensor.

This seems like it's gonna be a costly repair to hunt down.

 

from the service manual

HINT:
Use a torque wrench with a fulcrum length of 30 cm (11.81 in.).
(c) Observe these precautions when removing and installing
the injectors.
(1) Never reuse the O–ring.
(2) When placing a new O–ring on the injector, take
care not to damage it in any way.
(3) Coat a new O–ring with spindle oil or gasoline before
installing–never use engine, gear or brake oil.
(d) Install the injector to the delivery pipe and intake manifold,
as shown in the illustration.
Before installing the injector, must apply spindle oil or gasoline
on the place where a delivery pipe or an intake manifold
touches an O–ring of the injector.

 

Have the upstream O2 sensors ever been replaced? At 200k miles they are no doubt not performing like they used to. A missing O-ring will in theory allow extra unmetered air to get sucked into the engine.

 

You are welcome!
Might as well replace all three rear injector o-rings since the rear fuel rail needs to come out, then run some 5,000 mile fuel injector cleaner through the fuel system such as Berryman's BJ chemtool that costs around $7.00 a bottle to clean the injectors. Stay away from the injector cleaner that you use every tank as they are a waste of money! If the fuel filter has not been replaced you might want to have it replaced for prevention also.
Either an intake leak, or exhaust leak will cause a lean condition. An O2 sensor, or AF sensor doesn't detect fuel whether burned, or unburned, they only detects oxygen so if extra oxygen is getting in after the mass air flow sensor, the ECM won't know but will see the extra oxygen when it hits the O2 sensor and ramp up the fuel pulse again and again until the upper thresh hold is attained of around +25% and sets off the check engine light trying to keep the optimal 14.7 to 1 air fuel ratio. The exhaust at the tail pipe will smell rich, but the ECM will be saying you have a lean condition.
The ECM might also perceive a lean, or rich condition that doesn't exist if the AF sensor is contaminated, or defective, but they can be tested so as to not replace them needlessly when they are actually doing a good.

 

Thanks fortitude, every little bit helps!
I never knew they were such a crucial element to the injectors. It sounds like they're very serious about those rings.

I went to AutoZone and ordered a set of new O-rings for each injector.
Will be putting them in tomorrow. Do you have the illustration that goes along with this description?

I've only had the car for 2 months, and I haven't seen any reports saying that they were ever replaced, so they might be OEM since day 1 !

Thanks man, I hope that is just the case here, that this malfunction is happening because like you said, the un-metered air that's getting to the system.

I ordered the O-rings and will be putting them in tomorrow, or Wednesday. I'll also get some of the Berryman's cleaner as you suggested, I won't be using Seafoam, since I've tried it before.

Never replaced the fuel filter, anyway I can disassemble it and check for clogging? OR is it just a replaceable part?








Here is another 2 videos I took:
The car seems to lag a loooot, almost like drowning.
When my foot is on the pedal full throttle, the RPM goes to about 4,000 RPM and just sticks there meanwhile the speed will stay at where I was previously. So the car just stutters and RPM flies, while the car does not go up in speed.

BUT, the second I take my foot off of the pedal the car flies the way it should.

 

Sorry I'm posting so much info. Hoping that it will all help out in fixing the problem for me, and anyone who comes by the same situation I'm in. And you all do a great job of pointing towards the right direction and that really helps out.

I cleared the engine code and drove the car around a little bit today, when I came back home I thought I'd take 1 more reading and see if there are any hidden codes stored in the car.


It threw 2 codes as "pending", the same one from before, P0171(system too lean)
and the new code was P0300(multiple random misfire)







Got a new fuel filter for $23, will be putting it in tomorrow, along with changing the O- rings on all of the fuel injectors on bank 1 and 2. Then run some Berryman's B12 chemtool to clean out the injectors.

I hope this is the end, really hope so, I'm tired of this car, as it was just supposed to be a temporary car till the LS430 build was done with. Turned around and the ES bit me in the back!

 

King - what ODBC unit and software are you using with the iPhone? Most don't work because Apple locks the Bluetooth down to authorized Bluetooth radios.