2015 Infiniti QX50 stall when starting sometimes

Discussion of Infiniti's amazing (and underrated) sport-luxury crossovers, the EX35 and EX37. For 2014, the EX series will be renamed QX50, in line with Ininfiit's new naming conventions.
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VStar650CL
Posts: 2015
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby VStar650CL » Fri Dec 11, 2020 5:56 pm

You're most welcome, I think I speak for everyone when I say we enjoy a good puzzle. The intake temp with a warm engine and the car stationary will rarely reflect ambient, but at 5C, if you watched it at cruising speed it should fall way off because of ramming. Can you get STFT and IAT readings right after a cold start? Also have a listen to the injectors, they should be loudly firing all together when cold because the ECM is operating "open loop" (i.e., without feedback control from the A/F sensors). If the car is running less enrichment at idle than at speed, it's behaving dead-opposite to a vacuum leak. Since post-start idle is where you're having issues, if it isn't enriching enough, we at least have a tree to bark up. Cold enrichment should be very significant, cold engines resist running in ways warm ones don't.


sev
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Car: 2010 Infiniti EX35

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby sev » Thu Dec 17, 2020 2:53 pm

any updates?

rjkoop
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Car: 2015 Infiniti QX50 Journey

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby rjkoop » Thu Dec 17, 2020 3:50 pm

Nope. Same problem still. Hasn't stalled in a while but still drops (300rpm) low after warm startup. It's almost like it drops and it's either too rich or too lean and then recovers.

Richard

rjkoop
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Re: 2015 Infiniti QX50 stall when starting sometimes

Postby rjkoop » Sun Dec 27, 2020 7:04 am

Same problem still... And I have some time on my hands. Was thinking about doing a more exhaustive cleaning of the throttle body. I've read on some forums that you can cause issues with the throttle body if you move the throttle body's butterfly flap manually for a proper cleaning. Is that actually the case? Or if you perform the re-learn procedure afterwards you are fine?

I'm kind of surprised I don't get a check engine light to indicator any problem. Kind of thought the drop at warm startup to 200 or 300 rpm (almost stalling) would give me a check engine light for something. Temperature sensor issue, engine running too rich, too lean, etc...

Richard

Dzionassi
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Car: 2017 Infiniti QX50

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby Dzionassi » Sun Dec 27, 2020 12:17 pm

rjkoop wrote:
Sun Dec 27, 2020 7:04 am
Same problem still... And I have some time on my hands. Was thinking about doing a more exhaustive cleaning of the throttle body. I've read on some forums that you can cause issues with the throttle body if you move the throttle body's butterfly flap manually for a proper cleaning. Is that actually the case? Or if you perform the re-learn procedure afterwards you are fine?

I'm kind of surprised I don't get a check engine light to indicator any problem. Kind of thought the drop at warm startup to 200 or 300 rpm (almost stalling) would give me a check engine light for something. Temperature sensor issue, engine running too rich, too lean, etc...

Richard
You can move butterfly as much as you want with ignition off. Inner side of butterfly gets most dirt. You might need to do relearn.
Get your self new set of mafs:
https://www.ebay.com/itm/OEM-MAF-Mass-A ... 0005.m1851

Also check for leaks with smoke machine.

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

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby VStar650CL » Sun Dec 27, 2020 5:48 pm

Dzionassi wrote:
Sun Dec 27, 2020 12:17 pm
You can move butterfly as much as you want with ignition off. Inner side of butterfly gets most dirt. You might need to do relearn.
I'll confirm that. The throttle motor is a plain DC motor working against a return spring, the only way to harm the mechanism is to force it with the key in the on position. However, if you have an assistant or own a brick, the best way to inspect and clean is to turn on the key and floor the pedal. Pay special attention to the back sides and edges of the butterfly at the 12 and 6 o'clock positions, that's where the heaviest carbon will accumulate. An IAVL is de rigueur after cleaning, any carbon you remove from the bottom edges will change the rest position of the butterfly.

Johnnydangerus
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Re: 2015 Infiniti QX50 stall when starting sometimes

Postby Johnnydangerus » Sun Dec 27, 2020 7:08 pm

Add to cleaning of throttle body. After cleaning mine while they were on and moving the butterfly gently. Slowly releasing the butterfly back is the key I belive. And not forcing it too far back just enough to wipe and spray. Waited till next day before I started the car even made sure good n dry. Didn't remove because of gaskets and bolts and didnt want either of them to get damaged. I'd remove for best results if you have those things near by to buy if needed. High idle at start but went to spec in no time. Had my digital gas gauges all over the place for a few days but now steady. No light. Tried the relearn but with no light not sure if it worked? My idle has been great every start up but have noticed once warmed up and parked for a period of time it just started to bounce ever so slightly? Couple rpms?

Dzionassi
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Car: 2017 Infiniti QX50

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby Dzionassi » Sun Dec 27, 2020 8:18 pm

I never understood why people are freaking out about TB's. There is nothing there. It is like brushing your teeth. Butterfly, few gears and servo with spring.

Image

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VStar650CL
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2004 Nissan Altima 2.5 S

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby VStar650CL » Sun Dec 27, 2020 8:24 pm

Dzionassi wrote:
Sun Dec 27, 2020 8:18 pm
I never understood why people are freaking out about TB's. There is nothing there. It is like brushing your teeth. Butterfly, few gears and servo with spring.
Nice pic. I'll second that, they certainly aren't rocket science.

rjkoop
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Re: 2015 Infiniti QX50 stall when starting sometimes

Postby rjkoop » Mon Dec 28, 2020 7:18 am

Yep. I didn't understand that either. Seems simple to me. I just thought there was something special about the Infinitis. I've done it on Hondas/Nissans before... no problem.

Richard

rjkoop
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Re: 2015 Infiniti QX50 stall when starting sometimes

Postby rjkoop » Sat Jan 09, 2021 10:16 am

So I went to clean the throttle body better, it's cold here and this part broke off!

Image
Image

What's that part called? How can I go about removing it from the valve cover? Does it unscrew or just pull out? Argh!

Richard

sev
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Re: 2015 Infiniti QX50 stall when starting sometimes

Postby sev » Sat Jan 09, 2021 10:30 am

pics arent coming thru

rjkoop
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Re: 2015 Infiniti QX50 stall when starting sometimes

Postby rjkoop » Sat Jan 09, 2021 10:47 am

sev wrote:
Sat Jan 09, 2021 10:30 am
pics arent coming thru
Updated on google drive. Hopefully that works now.

rjkoop
Posts: 21
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Car: 2015 Infiniti QX50 Journey

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby rjkoop » Sun Jan 10, 2021 4:38 am

Do the pictures work now? From what I've read it's the crankcase breather tube. The one end of this tube goes into the crankcase (this is the plastic piece I broke off) and the other end goes back into the air intake tube (the hose on the bottom center of this picture).

Image

Richard

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VStar650CL
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2004 Nissan Altima 2.5 S

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby VStar650CL » Sun Jan 10, 2021 7:12 am

Yep, that's the purge tube for the PCV system. I've seen people repair them with a properly-sized pipe nipple but I'm not sure I'd recommend it. Replace the valve cover.

rjkoop
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Car: 2015 Infiniti QX50 Journey

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby rjkoop » Sun Jan 10, 2021 7:43 am

VStar650CL wrote:
Sun Jan 10, 2021 7:12 am
Yep, that's the purge tube for the PCV system. I've seen people repair them with a properly-sized pipe nipple but I'm not sure I'd recommend it. Replace the valve cover.
Yep. Probably the right way to go. Yesterday I JB welded the plastic piece back on. It actually sat really nice on the valve cover. I ensured a didn't clog the opening. So I'll try to reinstall the tube today. But long term... yes... I guess I've have to replace the valve cover... :(

Richard

rjkoop
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Car: 2015 Infiniti QX50 Journey

Re: 2015 Infiniti QX50 stall when starting sometimes

Postby rjkoop » Sun Jan 10, 2021 9:25 am

JB weld worked well. Car back together and works fine. Phew!

Lesson learned... don't just yank up on those rubber hoses if they are attached to plastic pieces. Work them off carefully.

Richard


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