So for the past six months or so I have had this problem on my 2007 AUTOmatic G35X sedan.

The problem typically occurs within the first 15 minutes of driving but not the first minute or two.

The most common symptom is from a dead stop there is a hiccup around 2k RPM. Ill start driving and the engine will rev to around 2k and the car will start moving and then the RPMs will fall to around 1200. Then the car will keep moving as normal, but the hiccup can be obviously felt.

Occasionally, around 2k RPM the tach and car will start stuttering. This has gotten worse and worse over time. It will be a +- 200 RPM stutter that gradually gets worse unless I step on the gas quite a bit. It is difficult to explain, but had anyone had this and found out what it was?

I'm really hoping it is not the transmission because I do not have the money for that right now. If anyone had any diagnostic help or advice that would be greatly appreciated. I will Venmo anyone who finds the correct fix 25$ if that motivates anyone (sorry I'm a broke college student).

Thanks!

 

Most of the time those symptoms come from a bad crankshaft sensor or bad camshaft sensors.

When that happens, does your check engine light come on? If yes, take it to your local auto parts store and have them read the code with their scanner.

If the codes do point to a faulty cam or crank sensor, then all u gotta do is replace them. They are all pretty easy to change. But ONLY use OEM replacement sensors. These cars dont work well with aftermarket sensors. All 3 of em will cost about $300 total.

 

CEL has not been on the entire time. Is there any way to narrow this down to this a bit before I try it? It may not be possible, but I'd really like to get this fixed on the first shot.

Could a more advanced code scanner identify this problem?

 

I can almost guarantee you're low on AT fluid, when was the last time you checked it? Also you MUST have the transmission up to temp so go for a 30 minute drive first, park the vehicle, cycle through each gear and let it engage them fully before shifting to the next, work down to 1st gear then back up to park with about a 2 second delay in each gear. Now leave the engine running, remove the 10mm bolt holding down the transmission dipstick, be sure to wipe the stick each time you check fluid and check it 3-5 times to get an accurate reading.

I think what's happening is when the fluid is cold it takes up quite a bit less volume so your initial driving is low on line pressure, then after a few momements (and clutch slipping which is what you are experiencing with those high rev problems) the fluid starts to heat up and expands to a larger volume which is just BARELY enough to keep the tranny from slipping again.

A slipping transmission isn't going to last you long, you've probably already caused significant damage to it by driving it like that for the last 6 months. The "stutter" is likely clutch slip inside the transmission, yes AT's have clutches.

These transmissions take Matic - J or Matic - S only.

 

So you think it is not the cam shaft sensors?

I will see If I can get the problem to occur in neutral/park.

When it is stuttering, it normally isn't during a time where the transmission should be shifting. I'm not sure if that matters. For what it is worth it had plenty of new looking fluid in it when it was checked about 9 months ago with no obvious signs of leaking. The car still does this in the "manual" shift mode.

I will do some more tests tomorrow.

 

Ok I thought the stutter and the shift issues were happening at the same time. Firstly check the connections on your battery, if everything is clean and tight and you aren't losing tach signal during the stutter then yes it MIGHT be a cam sensor. Without an oscilloscope though you would probably just have to replace all 4 of them. Only use Hitachi or OEM Genuine Nissan parts for cam/crank sensors.

 

Would it be worth resetting the ECU and other computers that you can be done from the drivers seat? I feel like it is an electrical problem, but my knowledge as you can see is quite limited.

Could it possibly be the torque converter? (hopefully not)

 

Taking it to a reputable transmission shop for a diagnostic would give the best results. You can "sort of" check the stall speed of the converter by just punching the throttle wide open from a standstill. You want to watch the tachometer, it will jump and sort of "stall out" at a certain rpm for a second or two while the car catches up, this is a lot easier to do in an X model because you have more traction. My guess is it should stall at like 1500 rpm but that's purely a GUESS and you would need to compare against some other people with an HR equipped G35.

If the stall rpm is fine the torque converter is PROBABLY fine.

You still need to check the fluid level as I explained earlier. Especially if it's been 9 months since you last checked it.

 

So it should stall around 1500 for a second or two? I can try that tomorrow, it is an X model.

 

That's purely a guess based on how other automatics I've looked at behaved. You will want to find another user with an HR equipped X to do the same thing so you can compare results.

It's more like "one full second", not really "a second or two". You'll see what I'm talking about when you do it, the rpm's jump/hang/car catches up/rpm's rise. That point where it hangs is an approximation of stall speed using a very non-scientific way of guessing that point.

If you do some google searching you'll probably see people suggest WOT power braking the tranny to test, I really don't recommend doing it, especially on a vehicle that you think might be having tranny problems. If you do then make sure it's a REALLY quick power brake, less than 2 seconds. That's how we used to guess stall converters on TH350 TH400 back in the day if you weren't sure how much stall the converter had. I'm not really sure how a modern transmission (let alone an X model...) would handle that kind of abuse unless it had factory transbrake / launch control and was sufficiently built to not just explode.

 

Okay. I feel the most helpful thing might be to take a video of the hiccup, and the rev stuttering and post it here. Thank you for the help, my offer stands if we figure this out.

 

Mr Dugan, May i try and see if your car and mine are doing the same thing; OK, right now its fairly cold here, so here is what my car does, (new battery last month btw) cars starts right up! always did, my car (69,000) miles will run flawlessly, up to a point, as it continues to WARM up, when my temp gauge gets close to operating temp, that is when my car will, not miss, but sort of bog, then go then bog again, this ONLY goes on for a 2,3 minutes at most, while i am driving the car slow, 30 mph or less to warm it up, once it gets to total operating temp, it runs as it did when brand new! ALSO, when its summer out, it still does it, but they get to operating temp so quickly its MUCH shorter as the car transitions from cold start to full temp. Now i am somewhat embarrassed to say this, but its been doing this for several Years! IMO, it has nothing to do with the tranny, mine is perfectly full and been changed twice in its life. i actually thought is was a throttle body issue, but when at full temp it runs flawless! i only say that because in the old days i had cars and trucks u had to choke them, ie maneul choke on a carb as to get them started and keep them running when driving, till they warmed up. So i have been living with this for several years, it only more annoying in the winter, because of longer warm up, anyway you said first 15 mins, and that caught my attention right away, because after 10 15 minutes, from cold start, thats when mine acts up, does NOT do this on hot start! btw , i have not taken my car anywhere for a tech to diagnosis this, caused i'd prolly have to leave it somewhere for a week, cause they'd only get one chance a day to drive thru how its acting up..... regards

 

Yes that sounds very familiar, by car is at 165,000 miles. Happens for about 1-2 minutes. The RPM's shake for that duration only under light acceleration. If I step on it a little it stops, but might continue again under light acceleration. Almost seems electrical.

By shake it goes down then and up in a predictable pattern. Not a hard shaking as the passenger normally can't tell.

 

If it's the cam/crank sensors I'd replace all three together with OE which is Hitachi. I got mine from rockauto for $125 for all three + shipping. My 05 had started being a little hard to crank than usual, then began missing periodically, and finally would just shut itself off and you have to work at it to get it refired. Put the set in and no further problems. It takes about 1-1/2 hrs in the driveway to do the job. You need a floor jack and a couple of jackstands and you will have to remove the undercover and everything from the breather top back to the throttle body. Cam sensors are at the back of the heads and I found it easier to unplug them after the sensor is out. Crank sensor is at lower driver's side of engine. All held in with 10mm bolt. About 2 Killians will do it, cheers.

 

I've done this at partial throttle (maybe 40%, maybe) and she held right around 2k for about 3 seconds before the ECU cut the throttle (oh fly by wire). I imagine the ECU will do the same at higher throttle positions.

Anybody know the OEM brand for the cam and crank sensors? Previous post mentioned Hitachi, but that's for an 05.