Qx4 Extremely High Idle, car isnt taking to relearn test

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CanuckQx4
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Car: 2001.5 Qx4 2wd

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Basically my car idles to high. My iacv failed on me, and the car would not run, it would die as you started it. I removed the iacv and saw the end cap had broken. So I found one at the junkyard off a clean looking engine.

Installed it, and now my idle jumps to 2200 when I start the car, and when fully warm only goes to 1300. No big deal I thought, I figured I could simply do the Idle Volume Air Relearn test on page EC-60 of the FSM, which is fairly simple, but my car will not take to that test. When I get to step #7 which is:

7. Disconnect throttle position sensor harness connector (brown), then reconnect it within 5 seconds.

As soon as I disconnect that connector my idle shoots up to 2000rpm and surges (bounces) like its hitting a limiter over and over. And as I plug the connector back in, the idle only drops to where it was before, about 1300.

Is this an idication that something obvious is out of spec??

After failing to do that test several times, I started diagnosing, and diagnosis step #4 on EC-60 says to check THROTTLE POSITION SWITCH CLOSED POSITION, and the procedure for that without consult II ends up being page EC-108. I did the test with the multimeter and I was not within tolerance, my car showed continuity until the throttle was openned .013" (quite out of spec), so I followed the procedure to adjust it, and got it bang on, and verified quite a few times after tightenning it. I then followed the RESET THROTTLE POSITION SENSOR IDLE POSITION MEMORY procedure, on page EC-110 #12 which is quite involved with turning the key on and off 20 times, and I believe I did it right but theres no way to tell.....

Then again I tried the Idle volume air relearn test and it did the same thing where the rpms jumped and surged when I pulled the connector off.

I am hoping someone can help me diagnose what is going on and what my ECU is upto with this. Im hoping Im just missing something easy, or something needs to be reset. Im thinking of maybe disconnecting the battery negative overnight... but dont want to mess anything else up. Appreciate any help!!


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Q451990
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Was the engine completely warmed up when you adjusted the TPS? If the throttle body has a fast idle cam, it will hold the throttle open a bit until everything is warmed up - resulting in setting the TPS incorrectly.

Heath

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CanuckQx4
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Car: 2001.5 Qx4 2wd

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I forget if it was warm.... but I would imagine so since I did the idle relearn test before Im sure. But just to be sure I will warm the engine and check the TPS again with the ohmmeter and feeler gauges.

I really need a better set of feeler gauges

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CanuckQx4
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Car: 2001.5 Qx4 2wd

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Could a faulty PCV cause the idle air volume relearn test to not be successful?

It is in the list of possible faults, but why would it affect this test from taking.

I have a new one, but its a multi hour job for the $3 part

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Q451990
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I would think so... any air entering the engine that's not supposed to could be a problem...

Heath

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CanuckQx4
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Car: 2001.5 Qx4 2wd

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$3 part, 3 hours labour lol.

Guess I will tackle it saturday

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CanuckQx4
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Does SteveTheTech not venture around here anymore??

Jeni
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Joined: Fri Dec 25, 2020 12:00 pm
Car: 2000 Infiniti QX4

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Hello, I have the exact same problem "high idle". After replaced with new IACV the problem did not go away. I have spent the entire weekend to
replace the IACV, TPS, MAF and clean the idle body but that did not fix the "high idle". I have adjusted the screw on the IACV, TPS and release the accelerator cable all the way down but my lowest idle at park is at 1,5000 RPM.

I have disconnected the neg. terminal and connected to the positive terminal to reset. I have turn ON/OFF 20 times. The vehicle is running good, it just the "high idle" at park at 1,5000 RPM. Is this normal? If I just keep like this will it cause anything? If this is the problem, can someone help me to fix the "high idle"?

Thank you so much in-advance.

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

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Try yanking a coil or two loose to get the idle down during IAVL. We run into this "catch 22" fairly frequently, where the existing settings stored in the ECM race the engine, but it refuses to relearn because the idle is too high. Slowing it down by rude measures is the only way out of the catch.

Jeni
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Joined: Fri Dec 25, 2020 12:00 pm
Car: 2000 Infiniti QX4

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I have yanked out two coils and started the relearning process again.
Procedure

- 1
Turn ignition switch "ON" and wait at least 1 second.
- 2
Turn ignition switch "OFF" and wait at least 10 seconds.
- 3
Start engine and warm it up to normal operating temperature.
- 4
Check that all items listed under the topic PREPARATION (previously
mentioned) are in good order.
- 5
Turn ignition switch "OFF" and wait at least 10 seconds.
- 6
Start the engine and let it idle for at least 30 seconds.
- 7
Disconnect throttle position sensor harness connector (brown), then
reconnect it within 5 seconds.
-
- 8
Wait 20 seconds.
- 9
Make sure that idle speed is within specifications. If not, the
result will be incomplete. In this case, find the cause of the problem by
referring to the NOTE below.
- 10
Rev up the engine two or three times. Make sure that idle speed and
ignition timing are within specifications.
- Idle speed = 700 ± 50 rpm (in P or N position)

My engine stopped running on step #6 after 10 seconds. Now I can't start my engine. I wonder if there's anything additional steps that I have to do. Thanks!

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VStar650CL
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We obviously use the CONSULT3+ at the dealership and I've never had occasion to try the manual procedure in concert with pulled coils, so I can't tell you how to remedy a no-restart. Doing the procedure with a scanner doesn't require killing the engine. You might need to find a scanner that has IAVL as a work utility.

Jeni
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Joined: Fri Dec 25, 2020 12:00 pm
Car: 2000 Infiniti QX4

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Okay, I got the ignition rotor and cap replaced and was able to start the car. The idle is going up/down between 1,500 and 2000 rmp. Should I take the car to the dealer for this? Any idea how much it would cost?

Thanks!

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mdmellott
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'02 Pathfinder SE 3.5L AT P/4WD
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Jeni wrote:
Fri Dec 25, 2020 6:09 pm
I have adjusted the screw on the IACV, .....
I have to ask, what screw did you adjust? There is no adjustment screw on the IACV. Are you referring to that tiny screw, with a dot of tamper detection paint on it, which sets the closed position of the butterfly valve in the throttle body?

Jeni
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Joined: Fri Dec 25, 2020 12:00 pm
Car: 2000 Infiniti QX4

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It was the screw on the IACV, that you can adjust to open or close. I have to close it to bring the idle down to 1500.

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mdmellott
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I see. Sort of. The relearn procedure you indicated is exactly what my '02 Pathfinder requires but I couldn't find that in the FSM for your '00 QX4. Your set up has a few more items than mine, like an IACV-FICD (fast idle control device) solenoid as well as the IACV-ACC. I'm just not familiar with all the other items.

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mdmellott
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It looks like the relearn procedure I use, the same one you reference, was not introduced until the 2001.5 models at the same time the IACV-FICD was eliminated from the engine controls. I don't think this relearn procedure is applicable to your '00 QX4.

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mdmellott
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Jeni wrote:
Sat Dec 26, 2020 2:29 pm
Should I take the car to the dealer for this? Any idea how much it would cost?
If you do not have a timing light, a vacuum pump, and a volt meter tp start with, you will not be able to check and adjust the necessary idle and timing components on your '00 QX4. The process steps required for doing this are far more manual on your vehicle than newer models. The FSM -Engine Control System pages EC-37 to EC-127 covers just about everything you would need to figure out what the trouble issue is. https://www.nicoclub.com/service-manual ... 0%2FEC.pdf I have no idea what the dealership cost to do this would be, nor could anyone tell you for certain until the issue is diagnosed. A diagnostic cost alone would be in the neighborhood of $195.


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