# 2012 Nissan Sentra - Idle Air Control Valve



## Gearic (May 13, 2021)

I want to clean my IACV, but I can't find any detialed engine diagrams to ensure I'm getting the right part.

My car started with problems only in reverse, but recently it is struggled when coming to a stop, and stalled on me more than once. Googling around on the symptoms all point to a dirt (or faulty) idle air control valve. I've watched a number of videos and read a few posts on how to clean it on other cars, but can't find somehting for this car, and none of the diagrams or videos look quite close enough that I'm comfortable taking off a part.

Maybe this all means I'm too novice to work on my own car 😅. I'm also worried the IACV in this car is just built into another component and it won't be as simple as it is on others.

Where can I get a detailed diagram on the engine compartment?
Or should Ij ust spend the $200 to get the part replaced by a professional?


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## rogoman (Dec 16, 2004)

Your engine does not have an IACV. The idle speed is controlled by the ECU which operates the throttle valve motor. It's all built into the throttle body. If the idle speed in incorrect, a procedure called "idle air volume learning" needs to be performed. You can download a copy of the FSM for your vehicle; it contains a procedure to do the "idle air volume learning". You can download a copy of the FSM from this web site: Owner's Manuals. The section EC.PDF is the one you need to read.


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## Gearic (May 13, 2021)

Oof, I asked the local shop for a quote to replace the IACV and they gave me a number at about $180. Who knows what they were actually quoting me for. I guess I won't be using them...

Thanks sio much for your help, I'll take a look there.


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## Gearic (May 13, 2021)

I've attached the relevant pages of the EC Manual. I'm having a bit of trouble.

There are 3 learning processes, and the Idle Air Volume Learning calls the other 2 as first steps.

The "Accelerator Pedal Released Position Learning" was simple enough, though I don't know if there's a way I can confirm it completed properly.

The "Throttle Valve Closed Position Learning" is giving me a bit more trouble. How am I supposed to actually check the coolant temperature? Should I be sticking a thermometor in the resevoir? The only temperature guage I have on the display is digital readout similar to the one shown here. I probably didn't start low enough for the steps shown. I also don't really know what it means by "confirming the operating sound". Should I have my head in the engine compartment listening for soemthing?

I moved on to the "Idle Air Volume Learning", and used a stopwatch to try and stick the timing as closely as I could. But, the MIL never started blinking. Is it possible it's because I didn't ge tthe Throttle Valve process done properly?

I'll also give a bit more details on the symptoms in another post.


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## Gearic (May 13, 2021)

From a cold start, the idle is slightly rough, but not terrible. After running awhile, it's better, but not perfect. When I shift to Reverse, the idle is notably worse. When accelerating in Reverse, it's very choppy, as if I'm tapping on and off the gas. That went on for a few weeks, and then I started noticing the engine wavering a bit when coming to a stop in Drive. I babied it a bit and came to stops very slowly, but recently it's stalled a couple times when in-town driving didn't really give me a lot of freedom to baby it.

When I come to a stop normally, the RPMs fall normally to about 1k, then right as I'm about to stop, they'll drop suddenly, the engine will rumble, and the then RPMs hover at about 250 for a moment, before returning to normal (~700-800). Occasionally, instead of returning to normal., the engine just stalls and shuts off. I can shift to park, adn start back normally with no problem.

Typically, when coming to a stop, I try to to decelerate early, and as I'm getting to about 1k RPM, I'll give it a little bit of gas, which gives a notable jerk, but then seems to handle the stop a lot better.

I haven't actually gotten a code for the MIL, but I will take it to AdvanceAuto tomorrow to plug it in.


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## rogoman (Dec 16, 2004)

Gearic said:


> I've attached the relevant pages of the EC Manual. I'm having a bit of trouble.
> 
> There are 3 learning processes, and the Idle Air Volume Learning calls the other 2 as first steps.
> 
> ...


I put together the 3 learning steps into a writeup; here's the writeup:


According to the FSM, the No load* (in P or N position) idle speed is 650 +/- 50 rpm. The idle speed is controlled by the ECU; there is no manual adjustment like they had on the old cars. If you need to bring the idle speed back down to spec, there is a procedure called the "Idle Air Volume Learning" which is a function of ECU to learn the idle air volume that keeps the engine idle speed within the specific range. It must be performed under any of the following conditions:
• Each time the electric throttle control actuator or ECU is replaced.
• Idle speed or ignition timing is out of specification.

Disconnect the negative battery terminal for 30 seconds to reset the onboard computer. Do not perform the relearn if the service engine soon light (CEL) is on and codes related to the mass airflow sensor, manifold absolute pressure, or incorrect idle speed are found. If everything is in order, we can begin.

First, bring the engine to normal operating temperature, 160-203°F or 70-95°C. Next turn off all accessories such as the air conditioning, rear window defogger, radio, and heater blower to prevent a load on the engine which would cause erroneous positioning of the throttle plate. Finally, make sure the front wheels of the vehicle are in the neutral position pointing straight ahead. We are now ready to perform the required relearn procedures:
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ACCELERATOR PEDAL RELEASED POSITION LEARNING 

1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON and wait at least 2 seconds.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Turn ignition switch ON and wait at least 2 seconds.
5. Turn ignition switch OFF and wait at least 10 seconds.

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THROTTLE VALVE CLOSED POSITION LEARNING 

1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Make sure that throttle valve moves during above 10 seconds by confirming the operating sound.

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IDLE AIR VOLUME LEARNING

CONDITIONS: Check Engine Light (CEL) with P0507 trouble code and high/pulsating idle, after disconnecting and reconnecting electrical to throttle position controller such as when cleaning throttle body.


TOOLS NEEDED: stopwatch or timer showing seconds.

1. When engine COLD, first perform the Accelerator Released Position and then the Throttle Valve Closed Position procedure as shown above.

2. Warm up engine at this point. Drive on the road for not less than 10 minutes.

3. Car in Park, turn off *all* electrical powered stuff, wheels turned straight.

4. Turn key OFF and wait at least 10 seconds.

5. Turn key ON (not ignition) and start stopwatch at same time.

6. When stopwatch is at 3 seconds, press & release accelerator pedal 5 times hard and quickly within 5 seconds.

7. Wait 7 seconds and fully press the accelerator pedal and hold for approximately 20 seconds until the check engine light stops blinking and constantly stays on.
(note: If the CEL never starts blinking, then something is not working and you'd better start over again).

8. Within 3 seconds after the check engine light stays constantly on, release the accelerator pedal.

9. Immediately start the engine and let it idle. It may still likely be a high-rev/pulsating idle.

10. Let it run for about 20 seconds, then rev the engine a few times.

11. With foot on brake, shift into Drive. Idle should now go down under 1000 rpm. Shift to Park again, and the car should find its regular idle speed. Operation will be normal except CEL may still be on. It may disappear soon on its own, or you can do the following:

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EASY RESET OF CHECK ENGINE LIGHT (CEL)

1. Turn key OFF and wait at least 10 seconds

2. Turn key ON (no ignition), wait 3 seconds, then press & release accelerator 5x hard and quickly.

3. Wait 10 seconds, then fully press accelerator.

4. After about 12 seconds CEL will go off then start blinking. As soon as it starts blinking, release the accelerator.

5. Wait 10 seconds, then fully press accelerator again.

6. Wait 10 seconds, then release the accelerator again.

7. Turn the key to off, then immediately start the engine. The CEL should be gone now.


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## Gearic (May 13, 2021)

Thanks, rogoman, it definitely seems that was a significant enffort. I'm not sure it clears up my confision, though.

Here are the codes I got from the diagnostic scanner:

P0131
P0101
P0725

I just got home, so haven't done my research yet, but will followup with what I find.


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## Gearic (May 13, 2021)

This part is completely cracked open. ~$80, should be in stack at the local store. I'll replace this part this weekend, clear the codes, and try again. The oxygen sensor is also a problem, but it looks like that's a major pain to get to in this vehicle, so I'll see what the codes do and report back.


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## VStar650CL (Nov 12, 2020)

Ignore the P0725, it's a "residual" code set because the ECM stopped sending engine speed when the P0131 occurred. Taken together, the P0131 and P0101 almost certainly indicate a vacuum leak. Since it's a Sentra, check the intake boot for cracks. They harden up and often crack out of sight on the bottom, but they separate when the engine rocks in the mounts on acceleration and suddenly the small leak becomes large. It causes exactly the kind of symptoms you describe, choppy acceleration, uneven performance, and often loading-up or stalling on deceleration.


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## Gearic (May 13, 2021)

The air intake tube had 2 massive cracks in it. Symptoms appear to be gone after replacing. I tried to clear the codes, but still getting check engine light. I'll run it for more codes probably Monday. It may be I didn't clear them properly, as I had similar trouble with the air volume learning, so I'll just ask them to clear the codes with the diagnostic reader.

Thanks for the help! I'll report back with any additional information.


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## VStar650CL (Nov 12, 2020)

Gearic said:


> The air intake tube had 2 massive cracks in it. Symptoms appear to be gone after replacing. I tried to clear the codes, but still getting check engine light. I'll run it for more codes probably Monday. It may be I didn't clear them properly, as I had similar trouble with the air volume learning, so I'll just ask them to clear the codes with the diagnostic reader.


You're most welcome! Those boots are a very common problem with Sentras. "Operational" codes like those won't usually clear with the engine running, you need to be key-on engine-off. If you tried to do IAVL before the leak was fixed, it's also probable the ECM is operating with bad airflow data, so re-perform it as soon as you get the codes cleared out or it will probably throw the same ones all over again.


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