i went through several pages to see if i can answer my own question before posting a new thread

i have a 2017 infiniti qx80 with 100,000 miles. The problem i'm having is RPM stuttering under load or when i go up a slight incline. The SUV started doing this around 85,000 miles. It's as if the transmission doesn't stay in the gear that is appropriate. Going up a hill the RPMs would hit 2200-2400 and then it would switch the gear to the next highest gear causing the RPMs to drop to 1700rpm. Then the SUV would stutter and you could see this with the RPM needle as it climbed from there. The car would shake as well with this action.

I've only had one code that stated it was a bad throttle body, the throttle body was replaced by infiniti and calibrated. I have also changed all the spark plugs. The MAS has been cleaned.

I have read somewhere a long time ago, i think in this forum, about others who have had this problem. They changed out a transmission and torque converter (under warranty) without improvement.

I'm at a loss at this point.

Could it be a bad fuel pump? Although, it doesnt act this way when parked and idling.
Coils?
Catalytic converter?

There is no check engine codes either.

Suggestions?

I was looking through the '17 QX80 owners manual https://www.infiniti.ca/content/dam/inf ... i-QX80.pdf and a '15 service manual https://www.nicoclub.com/service-manual ... 015/ma.pdf for the recommended maintenance service interval for transmission fluid. I was shocked to see that Nissan has indicated that no maintenance, inspection, or replacement of the transmission fluid is ever required, although the transfer fluid and differential gear oil has a inspection interval of every 10K miles and, if towing a trailer, using a camper or cartop carrier, or driving on rough or muddy roads, change (not just inspect) the transfer fluid and differential gear oil at every 20K miles or 24 months. So...If you use you vehicle in more extreme conditions, these drive train fluids and oils need changing more often than other SUVs and they need their levels checked more often than other SUVs but the transmission fluid never needs to be checked or replaced under any conditions. The absurdity of this indication that the transmission fluid lasts forever has my head spinning. Your description of problem symptoms with your QX80 appears to me to be transmission related. The process for changing the transmission fluid in a QX80 is not a simple process, as described in the service manual maintenance section. However, that is the first thing I would do to try and remedy the problem.

Driving conditions are normal. No gravel road driving, no towing. My wife is a sales rep in our state and is only on highway miles hence the increased miles in short period of time. I will check this out and see. I just hate having to eliminate literally everything to just fix it. When she drives on the high way or is going down the road not under load, the car acts as it should. Transmission temp is within spec as well.

No extreme wear and tear. That's good to hear. The "lasts the lifetime of the vehicle" scenario here is not the first time I've seen such a thing. Granted, vehicle manufactures' designs have improved a great deal over the past 10 to 20 years to provide higher reliability over a longer time frame but cost cutting measures are also part of the design considerations. I also have a Kia Soul+. It was designed with a fuel filter that was intended to last the lifetime of the vehicle under all conditions. I knew that was absurd as well. The "lifetime" duration is the vehicle manufacturer's expected period of time at which point, by design, the vehicle will self destruct. Extending that time frame with preventative maintenance that is not part of the manufacturer's scheduled maintenance is counter to manufacturers' sales so you will not find alternative official recommendations. When I finally replaced my Kia's fuel filter at 57K miles, I found the filter media to be so blackened and full of gunk it was only a matter of time before the fuel pump would fail from being over worked and the fuel injectors would foul. It may have gone 100K miles before that happened but that's what Kia considers its expected lifetime. Your QX80 should be able to realize at least a quarter million miles before it gives up the ghost but it will require more PM than Infinity recommends.

So go ahead and replace transmission fluid and filter and see if that helps?
I know my 2014 ram 1500 has an 8 speed ZF transmission that RAM is calling "lifetime." But in order to change the fluid/filter you have to change the entire transmission pan which holds the filter.
I'm assuming i might have to do the same with the infiniti or ill have to see how that's done.

Yep. That's what I would do. Since Infinity considered that service unnecessary within the "lifetime" of the vehicle, they did not spend the extra costs it would have taken to make this service easy for the DIY mechanic. Like my Kia's fuel filter. It was built into the fuel pump assembly, installed inside the fuel tank. It would have cost more to design the filter apart from the pump and external to the tank and easily serviceable. It was a pain to replace myself but I know it was worth it.

What OBD2 codes do you get, if any? I ran into similar stuttering under load just before my high pressure fuel pump (HPFP) lifter (part 13231+A) failed completely. The codes you'll see are P0087 and/or P0090. If you see those, get that rig into the dealer to have that lifter replaced before it completely fails and scores the eccentric camshaft assembly (part 13020+B) and the timing cover and you get a very expensive repair bill (or failed engine)

NM, I just saw this

I've only had one code that stated it was a bad throttle body

Just bought a 2017 QX80 three months ago and have the same issue...while starting off at low speeds it sputters like it wants to die but by the time I am at 45 or so, its fine. While cruising on hwy, no issue at all.

In stop and go traffic, the RPM bounces wildly between 1000 and 2000. Had code P2101 go off for throttle actuator motor. Replaced it and still the same thing happening. Got so bad after a week, took in again despite no codes showing. Replaced Mass Air Flow sensor and was told to use nothing but premium fuel.

After 3 weeks of that, still no change. Not sure if its a lemon or if all QX80s do this. Either way, its a pain as I am out more on repairs in 3 months that I am in car payments.

Did replacing transmission fluid and filter help as noted above?

Our 2014 QX80 is having the exact same issue. No issue at higher speeds and cruising highway, but sputters a lot below 35 during accelerating primarily (rpm jumped up/down about 500rpm's). I tried a couple tanks of premium fuel and it "seemed" to get a little better but still happening. Taking my car to the Dealership this week. If they don't have a clear diagnosis I might ask them to change the trans fluid/filter per the forum. I'll re-post after the service.

4XC wrote: ↑

Thu Jun 18, 2020 6:12 am

i went through several pages to see if i can answer my own question before posting a new thread

i have a 2017 infiniti qx80 with 100,000 miles. The problem i'm having is RPM stuttering under load or when i go up a slight incline. The SUV started doing this around 85,000 miles. It's as if the transmission doesn't stay in the gear that is appropriate. Going up a hill the RPMs would hit 2200-2400 and then it would switch the gear to the next highest gear causing the RPMs to drop to 1700rpm. Then the SUV would stutter and you could see this with the RPM needle as it climbed from there. The car would shake as well with this action.

I've only had one code that stated it was a bad throttle body, the throttle body was replaced by infiniti and calibrated. I have also changed all the spark plugs. The MAS has been cleaned.

I have read somewhere a long time ago, i think in this forum, about others who have had this problem. They changed out a transmission and torque converter (under warranty) without improvement.

I'm at a loss at this point.

Could it be a bad fuel pump? Although, it doesnt act this way when parked and idling.
Coils?
Catalytic converter?

There is no check engine codes either.

Suggestions?

Had this same issue on my QX around Christmas, turned out to be a bad coil on the passenger side. Replaced the coil and problem went away, but, I to had many miles on mine (118K), so when I made it back home from travel, I decided to replace the other 7, and I am sure glad I did, I found a total of 3 bad coils. The 1st one I replaced that was causing a big issue seemed to be leaking, when you take the boot off and look at the resistor between the spring and coil body, mine looked rusted but oily wet and the resistor was stuck in the body of the coil, this is actually the coil leaking, not a good thing. So when I took the other 7 off and inspected them, I found 2 more that had the same issues. My QX has been running like new under heavy acceleration and load, I highly recommend you replace your coils with so many miles, or at least inspect them. Hope this helps

-Adam

billerwin40513 wrote: ↑

Mon Apr 05, 2021 11:45 am

Just bought a 2017 QX80 three months ago and have the same issue...while starting off at low speeds it sputters like it wants to die but by the time I am at 45 or so, its fine. While cruising on hwy, no issue at all.

In stop and go traffic, the RPM bounces wildly between 1000 and 2000. Had code P2101 go off for throttle actuator motor. Replaced it and still the same thing happening. Got so bad after a week, took in again despite no codes showing. Replaced Mass Air Flow sensor and was told to use nothing but premium fuel.

After 3 weeks of that, still no change. Not sure if its a lemon or if all QX80s do this. Either way, its a pain as I am out more on repairs in 3 months that I am in car payments.

Did replacing transmission fluid and filter help as noted above?

Hopefully I can point you in the right direction.

Your issue is different than his, you have problems at low speed as his is under load. I have heard of others having, what they call, RPM surge. Not sure this is what yours is doing. But at lower RPMS, say 1500, and going at low speeds (25-35MPH), your RPMS start to surge, this is caused by your transmission shifting to far up (4 or 5), when you should be in a lower gear (2 or 3), to determine it isn't the transmission, down shift manually to see if the surging stops and the vehicle drives smoothly like it should while you manual shift. If yours cleans up after manually down shifting into a gear that you should be in, it's more than likely your fuel pump in the tank. Note sure how to explain why its the pump, but low pressure coming from your fuel pump will cause your transmission to shift way to early, causing a load on your engine that gives you that surge at low RPMs/speeds. You can do a search on Google, you will find a few people with early QX and even Armadas with 100K miles that discuss this surge issue. Again, I hope this helps and points someone in the right direction!

-Adam

RBooker1 wrote: ↑

Sun Apr 11, 2021 5:57 am

Our 2014 QX80 is having the exact same issue. No issue at higher speeds and cruising highway, but sputters a lot below 35 during accelerating primarily (rpm jumped up/down about 500rpm's). I tried a couple tanks of premium fuel and it "seemed" to get a little better but still happening. Taking my car to the Dealership this week. If they don't have a clear diagnosis I might ask them to change the trans fluid/filter per the forum. I'll re-post after the service.

Did you ever get a fix for your problem, might help others in the future, thanks and hopefully yours is fixed

from my experience with the same initial behavior, it's likely a failing hpfp lifter that hasn't yet completely broken through although is very close.

it's quick and easy to have a shop check for that and a new lifter is only $40 which could get you far enough to quick trade it in while it's running good. I wish I had traded mine in after that but i didn't and found that once the lifter falls, it scores the cam follower and timing cover which unless also replaced will cause more frequent lifter failures until you replace it all for ~$8000.

Had this exact same issue see service bulletin at link below, I had dealer reprogram ecu and tcm issue is now gone.

https://static.nhtsa.gov/odi/tsbs/2017/ ... 4-9999.pdf

Well, I have the fix, mine started doing this, so I dug very deep into the internet and found nothing. Talked to my buddy that has his own transmission shop back home where I'm from. He knew exactly what I was talking about and said many people always assume it's a spark issue, it's not, it's a torque converter issue in the Nissan and Infiniti vehicles. He did explain that flushing the transmission is very tricky, but talked me threw it step by step, and on top of that, I found a YouTube video showing how it's done.

But here is the fix, he said to add this additive from Life Guard called shudder eliminator. Bought it at my local auto zone. I drained just less than 6qts from the pan. I went and bought the Nissan transmission fluid from Infiniti at $13 a quart. Mixed in this sudden eliminator into the fluid and vacuum pumped the fluid back into the transmission. You have to refill the transmission while the vehicle is running to get the fluid level correct. I attached the video below that helped me understand what exactly to do and how.

I have taken my QX for a drive like normal, where usually I would get the shudder and sure enough, this thing is crazy smooth, no more shudder at low low speeds going up a speed incline. I really hope this helps others out in the future, Cassidy I am pretty excited... Good luck and Good bless!

Adam

https://youtu.be/ePPl56JWQq0