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Discussion Starter #1
I have new code p0171 and p0174
My question is.
What cause system too lean?

My car dont a thermostat.
Bad o2?

My o2 sensor are generic o2 sensor. Not denso sensor.

And i have a short intake. With conic filter.
 

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Also is bad to run without thermostat, ill take to long to heat up to operating temp and cause a check engine light, then 02 sensors this car is picky if you cant afford a new one find someone parting out same car make sure you get the right one there all different, short ram intakes are not very affective on our cars since we have a well sophisticated cai from the factory your only best upgrade would be the srt.
 

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Also is bad to run without thermostat, ill take to long to heat up to operating temp and cause a check engine light, then 02 sensors this car is picky if you cant afford a new one find someone parting out same car make sure you get the right one there all different, short ram intakes are not very affective on our cars since we have a well sophisticated cai from the factory your only best upgrade would be the srt.
Agreed on both your posts above, good advise. +rep

With no thermostat your car will not reach closed loop in the time the ecu is shooting for, not to mention while you are in open loop you are running inefficiently and hella rich which neither are good for the engine. Only cars that don't need or use a thermostat necessarily are race cars or hot rods, many just run restrictor plates I believe. Run a thermostat, they are cheap and easy to replace. Don't you like your heater to work in a reasonable time? Lol
Unless you have a supercharged race car then please disregard.

Things to check for causes of both lean DTC's....
-air induction system(any vacuum leaks, check near firewall driver side?)
-injector blockage
-MAF sensor(short ram may be an issue?)
-engine coolant temperature sensor(no thermostat and open loop stays open longer)
-ignition system
-fuel pressure
-gas leakage in exhaust system
-open or short O2 sensor (B2S1, B2S1)(are new generic sensor really doing their job?)
- PCV piping
-ECM

Anyways, I would recommend sticking to OE Denso oxygen sensors, all others including Bosch belong in the garbage. Sure they may work for a week but a Denso universal costs less than $40 off their site. No thermostat is either the problem or compounding it. Also, you said in another thread NGK iridium plugs were no good, that's simply not true. They just won't last as long as the Denso SK16R-P11 iridium plugs the Japanese put in our block from the factory(pregapped 120k mile plug). You'd be lucky to get 60k off NGK's.

You can easily put your primary O2's sensor signal on an oscilloscope and see the fast 0.1-0.9v fluctuations during CLOSED loop(I remember you saying you have one I think).

Things I would do to potentially correct the problem....
First, add a thermostat
Second, compare your B1S1 signal to B2S1
Third and maybe most important to your problem here, you say you have a short ram filter or intake, did the problems happen right after install? The IS300 is picky when it comes to short ram intakes because not only can turbulence cause a MAF issue, unmetered air issues or high IAT issues(which is why some require a heatsheild if they sit over the exhaust header), just do a quick search and you'll see the AEM and short ram issues. My advice, ditch the intake and put the factory box back on. The engine is likely better off, OE intake has very little restriction compared to many other intakes.
Fourth, ditch the $20 O2 sensors for Denso universals and properly splice them in.

Then I bet your lean codes go away, just my thoughts. I'm not trying to sound like an A$$ and trying to really help but I believe in "you get what you pay for" and we all know cheap O2 sensors are a bad idea. So honestly I can't point my finger at just one issue I see here.
/rant
 

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Discussion Starter #5
hi..

jason you say that .. Things to check for causes of both lean DTC's....
-air induction system(any vacuum leaks, check near firewall driver side?

but exactly where find vaccum leak. you can post a pic?
 

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hi..

jason you say that .. Things to check for causes of both lean DTC's....
-air induction system(any vacuum leaks, check near firewall driver side?

but exactly where find vaccum leak. you can post a pic?
Hi. Yes, unmetered air or a vacuum leak are common causes of running lean. It's pretty hard to get an actual shot of the bay vacuum lines because the intake manifold covers most and they sit down in between the runners. There's a reserve tank for the ACIS and many connections are not clamped at all. Unmetered airflow can cause the car to run lean, so verify there are no leaks between the MAF and throttle body. Make sure the throttle body gasket is in good shape, no cracks, obviously. Sewell has these vacuum lines pretty well played out. Remember you have piping there for gas tank pressure regulation as well as vacuum lines into the intake side and for the ACIS. Hope this helps, see the link for a description of the parts.

2005 IS300: OEM Engine & Fuel (VACUUM PIPING) Replacement Parts


But as previously mentioned, it could be a few things. Fuel pressure is one, should have about 44 psi to the banjo bolt and fuel rail. Verify the MAF is giving the correct readings at idle and 3k rpms. Specs are as follows..

MAF
•Idling
3.5-5.0 gm/s
•Racing without load(2,500 rpm)
12.5-17.9 gm/s

The MAF can read a range from 0 to 655 gm/s. It goes further into detail when setting the different MILs(codes) and the ranges the MAF sees and what it will fault at. That's on page #264 or DI-70.
It's also good to know the spec calculated load because the MAF directly affects it, plus I haven't seen it listed here.

Calculated load
•Idling
15.6-22.2%
•Racing without load (2,500 rpm)
16.6-23.9%
•With parking brake set and foot on brake in drive and at 3,000 rpm or greater
Greater than 75% should be achieved with a load.(not from DI book)
 

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Discussion Starter #7
here post the log frezze frame by torque

Freeze frame report generated by Torque for Android
=========================================================

Vehicle VIN: Not present
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: 15313001
35301100

Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 16.078 %
Engine Coolant Temperature = 81 °C
Fuel Trim Bank 1 Short Term = 17.969 %
Fuel Trim Bank 1 Long Term = 34.375 %
Fuel Trim Bank 2 Short Term = 19.531 %
Fuel Trim Bank 2 Long Term = 15.625 %
Engine RPM = 648.25 rpm
Speed (OBD) = 1 km/h
Intake Air Temperature = 51 °C
 

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huh?? how do you guys know whats going on? I feel like i'm trying to read brail in shorthand... lol
 

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huh?? how do you guys know whats going on? I feel like i'm trying to read brail in shorthand... lol
Any advanced obd2 scanner will usually work, as well as a techstream 2.0 the dealers use.;)

here post the log frezze frame by torque

Freeze frame report generated by Torque for Android
=========================================================

Vehicle VIN: Not present
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: 15313001
35301100

Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 16.078 %
Engine Coolant Temperature = 81 °C
Fuel Trim Bank 1 Short Term = 17.969 %
Fuel Trim Bank 1 Long Term = 34.375 %
Fuel Trim Bank 2 Short Term = 19.531 %
Fuel Trim Bank 2 Long Term = 15.625 %
Engine RPM = 648.25 rpm
Speed (OBD) = 1 km/h
Intake Air Temperature = 51 °C
To see both banks like that tells me it could still be MAF related, fuel pressure related, vacuum issue or unmetered air. Try setting the parking brake and put one foot firmly on the brake pedal and then try to give it some gas to see if you can achieve a calculated load of near 75% or higher. If it doesnt go above 50-60% your MAF may not be reading airflow right, which is the reason I posted the airflow specs straight from the DI book.
 

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You rang? Lol

I see a few things that are concerning. Look at the specs I have for intake air speed and calculated load, yours look low. See the third chart up, at about 1000 rpms you have a 0.7g/sec flow rate, all other times it's 3g/s or lower. Spec is 3.5-5g/s. At 3k rpms it should be 12.5-17.9g/sec.
Also your calculated load is low compared to the specs I posted, try setting the parking brakes and push the gas and hold the brake pedal and see if you can achieve a calculated load value higher than 75%. At idle it should be at least 15.6% and you are way low. This could simply mean the MAF needs cleaned or is faulty in my opinion, both calculated load and intake air speed is majority relied on the MAF.
 

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Discussion Starter #14
You rang? Lol

I see a few things that are concerning. Look at the specs I have for intake air speed and calculated load, yours look low. See the third chart up, at about 1000 rpms you have a 0.7g/sec flow rate, all other times it's 3g/s or lower. Spec is 3.5-5g/s. At 3k rpms it should be 12.5-17.9g/sec.
Also your calculated load is low compared to the specs I posted, try setting the parking brakes and push the gas and hold the brake pedal and see if you can achieve a calculated load value higher than 75%. At idle it should be at least 15.6% and you are way low. This could simply mean the MAF needs cleaned or is faulty in my opinion, both calculated load and intake air speed is majority relied on the MAF.
my value of the engine load is

full parking branke and full brake
at 2900 rpm full throttle the engine load is 74%,
the rpm no up more of 2900 rpm.

any idea?
 
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