Hi There, My 2019 Q70L 3.7 11k miles has been hesitating to normal response to accelerator position on some random and rare occasions at cold start.

Here is how it happens, start the car cold, wait 5-10 sec put in gear and slowly drive away but when push the accelerator, no response from the engine occurs to the same amount of pressure on the accelerator, lets say I push the accelerator all the way engine only revs up to 2300 RPM, then I let go of accelerator and push again for couple of times it goes in normal mode.

This has happened 5-6 times over the past nine months of ownership, so I am sure it will be one of those cases that dealer say they can't duplicate.

Is your Car new
Does it have a warranty
If yes I’d take it to them then go from there.
It sounds like it was in a limp mouse at first but it wouldn’t correct itself
It sounds to me that there is a ground or a connection that isn’t quite right but with acceleration it “jumps” the junction.

Sounds like something simple I HOPE

good luck
Keep us posted
And

When you say 'cold start' - what is the actual outdoor temp when this happens? Sometimes a weakened fuel pump may not be able to pump fuel efficiently until it warms up - or maybe it's a sensor related issue. You're right though. The car will need to sit overnight at the dealer with you sat home crossing your fingers that it acts up for the tech the way it does for you. Please post the outcome so other Q70'ers will have a reference.

Thanks for Replies. Car was new when purchased. hesitation (randomly) only happens at cold start regardless of ambient temperature. It seems it happens more often if I put the car in gear before the cold start idle drops to 1000 RPM. It doesn't seem like its lose connection or anything like that as all the functions of car perform flawlessly except acceleration, it even idles fine.

I brought this up to the dealer at 5K service and obviously I got the typical answer of "never heard of this before". One thing I say is the car has KAHU vehicle recovery system installed on it by the dealer from new and I am wondering maybe that is interfering with the electronics on the random basis.

I want to make sure I'm understanding this correctly. You start the car up and within 10 seconds put it into drive and drive away? I would think you would need the car to warm up a bit before taking off, unless I'm just missing something.

reggiebrown40 wrote: ↑

Mon Dec 23, 2019 6:55 am

... I would think you would need the car to warm up a bit before taking off, unless I'm just missing something.

Not really. The most efficient way to warm a vehicle up is to drive it. I believe I have also seen it in an owner's manual.


To the hesitation that Kami mentioned, I'd also just tell the dealer to keep it until they figure it out. You have given us a good amount of info to start from, but if you can catch it on video, that'd be even better for the service department.

I don't drive away like spirited driving, warming up driving away until the engine temp rises. I actually have one of it on the video as I keep pushing accelerator and RPM doesn't go over 2300 RPM.

As far as leaving it at the dealer for a while, I don't feel comfortable doing so as they usually gave the car back to me with minor scratches and even once a ding that I could not prove it wasn't there before.

Might be a good idea to also make a video of the issue so the dealership can try to recreate it based on the video.

EdBwoy wrote: ↑

Mon Dec 23, 2019 7:07 am

reggiebrown40 wrote: ↑

Mon Dec 23, 2019 6:55 am

... I would think you would need the car to warm up a bit before taking off, unless I'm just missing something.

Not really. The most efficient way to warm a vehicle up is to drive it. I believe I have also seen it in an owner's manual.


To the hesitation that Kami mentioned, I'd also just tell the dealer to keep it until they figure it out. You have given us a good amount of info to start from, but if you can catch it on video, that'd be even better for the service department.

Warm up a bit as in give it at least 20 seconds for it to exit closed loop. The owner's manual is most likely referring to they way people used to let their cars warm up for 5 - 10 minutes before driving off, which is excessive. However, It's not unreasonable to give the car 30 seconds to a minute to "warm up." Especially in cold weather.

OP, what would happen if you gave the car an additional 20 seconds or so to idle normally? Would the issue ever come up?

I usually let it warm up at least 30 sec or till the RPM drops under 1000, I don't remember it has ever happened in that situation, however in occasions I shift in gear and driven away without waiting that long an issue appeared more in those occasions.

I think when you immediately try to drive without letting the engine exit it's closed loop process, it may be confusing the computer a bit. As long as your engine drops down to normal idle and you drive away and you have no acceleration issues then everything is functioning normally.

You're right about that Reggie. I assumed we were talking about the old habit of waiting for the needle on the coolant gauge to rise before driving off.
Infiniti does in fact instruct you to let it idle for about 30 seconds at startup.

I know I usually take a good part of a minute to drive off after I push the button. That's the time I usually take to buckle down, make adjustments, and generally just listen to my vehicle.
I might make a poor getaway driver, but I am a good custodian of my vehicles.


***
Talking of old school habits, here's another one to baffle the masses - Infiniti also tells us to let the engine idle for a few minutes before shutting it off.

reggiebrown40 wrote: ↑

Mon Dec 23, 2019 2:56 pm

I think when you immediately try to drive without letting the engine exit it's closed loop process, it may be confusing the computer a bit. As long as your engine drops down to normal idle and you drive away and you have no acceleration issues then everything is functioning normally.

I also believe this could be some sort of program driven by ECU to prevent a cold engine from revving up, but in cases that I came out of my work garage and had to accelerate to the flow of the traffic it had stalled me for couple of times and that was not pretty.

EdBwoy wrote: ↑

Tue Dec 24, 2019 4:01 am

***
Talking of old school habits, here's another one to baffle the masses - Infiniti also tells us to let the engine idle for a few minutes before shutting it off.

Yes talking old school deisel engines, my dad had a 1978 MB 240D and that you would have to let idle to cool down few mintues in driveway before shutting off. But thats crazy for 21 century vehicles! Infiniti needs to step up their games. lol

kami_sn wrote: ↑

Mon Dec 23, 2019 7:43 am

As far as leaving it at the dealer for a while, I don't feel comfortable doing so as they usually gave the car back to me with minor scratches and even once a ding that I could not prove it wasn't there before.

If you are one of the unlucky ones with a terrible dealer, just take a video walk around of your car on their lot prior to handing them the keys. Make sure to record the dealership building/signage, etc. State the time and date on the video and purpose of the video.

EdBwoy wrote: ↑

Tue Dec 24, 2019 4:01 am

You're right about that Reggie. I assumed we were talking about the old habit of waiting for the needle on the coolant gauge to rise before driving off.
Infiniti does in fact instruct you to let it idle for about 30 seconds at startup.

I know I usually take a good part of a minute to drive off after I push the button. That's the time I usually take to buckle down, make adjustments, and generally just listen to my vehicle.
I might make a poor getaway driver, but I am a good custodian of my vehicles.


***
Talking of old school habits, here's another one to baffle the masses - Infiniti also tells us to let the engine idle for a few minutes before shutting it off.

Yep the exhaust note is more aggressive in closed loop. It's definitely more pronounced with a custom exhaust. You can hear it quiet down, as if someone turned the volume down after about 25 - 30 seconds once it warms up.


Didn't know about Infiniti including the idling before shutting the engine off recommendation in the owner's manual. It mentions doing this during cold weather. I've also heard of doing this after spirited driving with turbo charged vehicles, to help normalize bearing temps. I do it all the time anyway, not for a few minutes but maybe 30 seconds or so, mainly to listen for any abnormal noises, especially after the lifter bucket issues. For normal driving in warmer temps, I guess it's ok to shut off after you're parked.

That's right! once a combustion engine turns off the heat soak situation happens which is due to the fact that you don't have cooling systems functioning in the engine that still has heat stored in it's parts, in old cars when they would get older this could become a big issue as it also could cause warm start issues as the fuel would evaporate when sitting.

What I do after 20 miles of freeway driving going home/work (Texas freeways) when I get off the freeway, I have another 2-3 miles to get to my house/work, that's were I cool down the whole car by old man style driving (low RPM cruising). In general it feels the 3.7 engines run pretty hot, specially in summer this car feels like a furnace, my 3.5 Murano was not as hot as this.

Ilya wrote: ↑

Tue Dec 24, 2019 8:14 am

kami_sn wrote: ↑

Mon Dec 23, 2019 7:43 am

As far as leaving it at the dealer for a while, I don't feel comfortable doing so as they usually gave the car back to me with minor scratches and even once a ding that I could not prove it wasn't there before.

If you are one of the unlucky ones with a terrible dealer, just take a video walk around of your car on their lot prior to handing them the keys. Make sure to record the dealership building/signage, etc. State the time and date on the video and purpose of the video.

That's a good idea Ilya, however I don't like to cause unnecessary damage to my car, that's why I try to avoid going there as much as possible. On a black car even single dust can be spotted from a mile away.