My car has this problem in 1st and 2nd gear. When I get on the throttle (50-75 %) it starts to take off and I'm pushed back in my seat and then the RPMs will move through the band without any acceleration, I kind of fall out of my seat, expecting to be pushed through. It seems the power fluctuates throughout the powerband. It doesn't happen always, usually when I try to acceleration from a stop. I thought it was the TB being too dirty, but after a cleaning it makes no difference. I've had 1 coil replaced with no difference also.

 

Dont know how many miles you got on the car, but sounds like issue with Injectors. Seem like they are clogged or getting there.

Dixit

 

I have 50k miles on my car. I was considering this. Should I get some BG44k?

 

If the engine is spinning up "RPMs moving through the band" but you don't go anywhere, you need to check your transmission. I bet your clutch is slipping.

 

I don't think it's the clutch. I'll put it in gear--any gear--but even 5th and cruise at 50mph and then WOT and it doesn't slip. It has to do with the engine. It's hard to explain but I'm pretty sure it's not the clutch.

 

If the engine accelerates (RPMs increase) but the car does not, you have transmission problems. It may not be clutch slippage, but I bet it's transmission from your description.

Also, keep this in mind:
mechanical advantage (gearing) is much greater in first and second gear as compared to 5th gear. If the transmission is going to fail, that is a significantly more likely place.

Do the RPMs climb quickly when in first and second gear even though the car does not accelerate quickly?

I would get the car to somebody very soon. It is always possible for a transmission problem to leave you stranded or be destroying other components in the mean time.


Make sure to let us know what you find.

 

Would you still consider this a clutch problem if the symptoms disappear during WOT? Because they do.

 

If the RPMs keep rising, but the car does not accelerate, then look at the transmission. It may not be the clutch itself. It may be elsewhere in the transmission. However, if the change in RPM seems to be inconsistent as you say the acceleration is, then it is likely not the tranny.
Think about it, if the engine is spooling up but your wheels aren't, what is in the middle?
I'm by no means an expert, but I you posted asking for help and I have presented my opinion based on your description.

 

If the transmission itself had a problem you would hear horrible noise or be unable to select a gear etc. According to the description given, the behavior sounds like clutch slippage. The only thing that gives between the engine and the tranny is the clutch. Do you smell anything burning after a good session of stop and go driving? Does the behavior get worse while starting off from stand still and accelerating on an incline (big hill)? That would give us more to go on :-)

 

I had a problem like that since I bought a 2000 maxima. But it happened from the beginning. I mean I bought it 4 months ago with 87000 mileage.
The car would go fine if I pressed the pedal easy.( back then I assumed it was okay), but when I pressed the pedal to the bottom it kind of stopped responding. RPM's went up to 6000 but the car got like stuck on 50 mph.
It would not accelerate.
But after while I got check engine light on.
It always showed the same code P0171 and P0142 - system too lean, bank 1 and oxygen sensor.
I was worried I would have to replace oxygen sensors, when I read that someone had similar problem and it was MAF ( Mass Air Flow ) sensor.
100 dollars from the dealer fixed my problem. Maybe it is something you should consider.
I don't know how to check that sensor.
The car's computer would not give any code relating to that sensor.
I just replaced it first before replacing oxygen sensors and it was it.
Now I know how fast this car accelerates. It is AWESOME.
Stupid sensor caused me so much headache, but now it is gone.
About your transmission. With 50 thousand miles on it it should run like new.
I do not believe in transmission problems with that mileage in maximas.
Do you get any check engine light warnings?
I also did RunRite fuel system cleaning.
Right after that the car was even worse than before, until I replaced MAF sensor.
Try to test that sensor. Very easy to get into it. Right on top, behind air filter.
You will see.

 

I understand what you're saying. I was by no means trying to insult you, I hope you're not offended. My bad if I did.