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7

We found at least two issues The air filter housing wasn't forming a proper seal with the MAF sensor This engine boasts a quirky design where the MAF sensor sits at the back of the engine. The air filter housing seal is in the middle of this first picture, MAF sensor in the second picture (stills were taken from this video). Whoever had installed it didn'...


6

Using your scan tool watch fuel trims at idle, then while still stopped @ 3000 rpm. Fuel trims going to normal (anything below LTFT 10%) when revving point towards a vacuum leak or faulty MAF. To check the AFR sensor pull a vacuum line with the engine running and it should go high lean. Then introduce fuel and it should go high rich. Toyota/Denso sensors ...


6

Great question, you supplied enough data to give direction and this is a common problem. This pattern of fuel trim behavior, higher positive at idle than at cruise speeds, is commonly seen when the mass air flow sensor gets dirty. Inspect with a strong light and a minimum of 3x magnification. Look down the small rectangular hole and see if the two small ...


5

This should not cause you an issue, but this sounds more like a problem with the O2 sensors than with the intake gaskets. When was the last time you had them changed? If you are over 100k miles without new ones, I'd highly suggest this first. One way to check your theory for the intake gasket is by using a spray bottle with water (on jet, not spray). With ...


2

P0171: oxygen sensor in bank 1 has detected a lean condition (too much oxygen in the exhaust). the side of the engine that has P0171 is one of the more common trouble codes. This code is triggered by the first downstream (front) O2 sensor. Bank #1 refers to the side which has cylinder #1, In a 4 cylinder it is the cylinder in the front of the engine. The ...


2

The main cause of most P0171 codes on the 4runner is the MAF sensor, which also has the air temperature sensor on it, a faulty air temperature sensor on your MAF can cause a running rich problem. It's possible that the MAF may be the wrong one for the engine as well, or an inferior part, if it's a project car who knows what was done to it before you got it. ...


2

@Fred Wilson's comment is right on the money, high, positive long term fuel trims at idle that reduce at higher engine speeds indicate the presence of higher-than-normal unmetered air. The fact that it's unmetered indicates that you need to look for something after the MAF/MAP sensor. Things to check include: Unplugged/damaged hoses (e.g. EGR, PCV) ...


1

My suggestion is to look at the throttle body, specifically at the throttle position sensor (TPS). You need to see if it has the right output. You can either do this by looking directly at the computer (through an OBDII device), or by measuring the output at the TPS itself using a multimeter. In either case you'd be looking to ensure there is a clean sweep ...


1

Ugh.. Corsa-Ds seem to throw this code for everything, sometimes just because the day ends in a "Y" A failing Manifold Absolute Pressure (MAP) sensor is the usual culprit - particularly with the intermittent nature. If the MAP is failing you'll see the code when accelerating hard or the engine is under load (which means when it's just sat there at the ...


1

LTFT1 39.8 This sticks out like a burr. The lambdas are sensing 40% more air than what the MAF/MAP is measuring, either due to unmetered air or insufficient fuel. Given that the MAF and lambda sensors have been inspected or replaced I don't think this is an issue related to false readings. If there's a gaping air leak somewhere, it can be confirmed by ...


1

I can only speculate why no freeze frame data is being stored with the p0171. My "guess" would be that it is a 2 trip code, and you are seeing a pending code on the first trip. When it comes to p0171, you don't really need freeze frame to help you out. Since this code is a direct result of fuel trim, the next logical step is to see if the total fuel trim, ...


1

If the throttle body, MAF/MAP was cleaned, or other fuel/emission components replaced, the throttle relearn needs to be done. Disconnect the negative cable from the battery (cover the post with a cloth to avoid shorting). Disconnect the positive cable from the battery (cover the post with a cloth to avoid shorting). Touch the positive and negative cables ...


1

LTFT at 29.7% seems mighty high. I'd start by looking for unmetered air leaks aka "vacuum" leaks. Unmetered air might be fooling the primary O2 sensor - so called "false lean". Easy to check and a standard part of my KISS rule/Occam's Razor mantra. Interesting about the "reverse" stalling comment. My spidey sense says to check any rubber or plastic intake ...


1

In general, these codes indicate that the ECU receives information about fuel mixture being too lean, ie. too much oxygen, too little fuel. Therefore, it is trying to compensate by adding more fuel (see the long term fuel trim values which are pretty high). This is done according to A/F sensor readings. Things to check: MAF - hypothetically could be faulty,...


1

It sounds like a vacuum leak. Is it possible that in replacing the cold air intake, a gasket did not seat correctly or the install did not follow the correct torque sequence or values? Also check all the vacuum hoses that are attached to the intake. You can also isolate the spot by spraying carb cleaner around the intake with the engine cold but running and ...


1

You may have already fixed your problem You may need to clear the codes for the Check Engine Light to go away. It may be that the sensor is clean but the check engine light is being shown because it's retained in the computer's memory. Once the codes are cleared, see if the CEL stays off or if it returns. If the issue returns P0171 is saying that the ...


1

Bank 1 on any engine is the bank that carries No 1 cylinder. Sensor1 is the first sensor from where the exhaust manifold bolts onto the engine/head. Some scans will show an 'N/A' on a four cylinder engine for Bank2. This means that the ECU is programmed for a four cylinder, but can be programmed for a 6 or 8 cylinder vee using differant software. Your ...


1

Code P0171 is a pretty general code for 'engine running weak'. Running weak means too much air, or, not enough fuel. The main culprits are a loose or damaged vacuum hose, EGR valve staying open, EVAP system leaking air into the system, faulty fuel injector(s), or a leaking exhaust system. It does not seem to be the oxygen sensor to me because you have rough ...


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