RPMs bounce while going less than 50mph in 5th gear
 

My 5AT '05 TL with about 22,500 miles is mostly driven in the city so the average MPGs is :ugh: (around 23). My brother and I use the Sequential Sportshift to shift into a higher gear to get the RPMs lower and therefore get better gas mileage. The problem is that when either of us shift into fifth gear going less than about 50mph (but above the 37mph that the owner's manual says is acceptable to shift into 5th), the RPMs constantly bounce about 200-300 RPMs and the engine and maybe the transmission sound louder and like they're working much harder than in any of the other gears. When I'm going above 50mph, the engine/transmission seem to stop sounding like they're having problems and the RPMs stay constant. The obvious solution is to stop shifting into 5th when I'm going less than 50mph but the fact that the RPMs bounce like crazy leads me to believe that there might be a problem with the transmission. I'm going to take the car to a dealership but I'd like to know if anyone else has had the same problem (I searched the issue but found nothing so sorry if this is a known issue).

it bounces because you are restraining the motor, RPM's should always be kept above 500, even idle is 750... Keeping it at 200-300 may cause some damage to the internals as the motor is bogged down as it has almost no power then to power up the electronics and move the car. Lastly, I do not know what you did, but I don't think SS will allow you to upshift if the RPM's are that low.

With an auto, it is not possible to lug the engine like one can with a manual trans.. The stall converter in our TL is approx 2,000. Therefore, IF IT WAS POSSIBLE (just to make a point) to start off in 5th gear, the engine will instantly jump to approx 2,000 RPM (provided the converter's lock-up was not engaged).

Sorry for not being specific enough - the RPMs bounce from about 1,300 to maybe 1,600, not from 200 to 300 RPMs.

Just leave it in auto for normal driving.
It changes back and forth as you apply the gas or not?
That's the torque converter, it's supposed to do that.
No worries.

The last time I "manually" shifted into 5th, I had cruise control on while going 47 mph (the speed limit was 45 so I didn't want to go too much faster than that) and even though the car was going at a constant speed on a straight and level road and I wasn't pressing the gas or brake, the RPMs were fluctuating between about 1,300 and 1,600. I was going ten mph above the recommended speed to shift into fifth gear and it sounded as if I had slammed it into first. That can't be normal.

Even at 50 MPH when it shifts into 5th by itself it does the rpm fluctuations (even with cruise control on), but it is not just for a few seconds, it goes on for quite some time (over 30 second) on very flat florida roads. I drive the same roads with my CL-S and the 06 Pilot and it doesn't do behave like it does in the TL.

<----His brother BTW and I drove the car for two weeks while I was waiting for a new trans

Take it in; it's still under warranty.

I can get a video of it occuring if necessary. The acura dealership is a decent trip away (even thought we have a Honda dealership 1 mile away), so we just want to see if its normal or something to take it in for warranty work.

I am in the same boat, the RPM's bounce about 100-200 RPM in the 1500-2000 RPM range. Most of the time it is around 45-50mph. My wife and I both get annoyed by it.

Is this a normal occurrence? Our Acura dealer is over an hour and a half drive for maintenance.

Our '06 TL does the same thing when cold on flat, S. Florida roads. The dealership mechanics gave it a "could not reproduce", even when the car was left overnight to test first thing in the morning.

The easiest solution I've found is to simply avoid that cruising rpm range until the car warms up. If it does it, I just shift it manually to 4th and let it warm up fully before returning to 5th.

Either the torque converter isn't locking up correctly, or the software/logic driving the torque converter is sending oscillating instructions. The car's run out of warranty, and I don't think this issue requires fixing. Just a quirk of the car.

thanks for the answer. We do not have a local dealer, so I dont think I will go 1.5 hours away to have them do the same thing.

Just for the record, I have the exact same problem. 2006 TL, 5AT, if I drive at 46 mph on level ground, the rpm will oscillate 200 RPM or so from 1300 to 1500. It has gotten noticeably worse, so something is wearing out, just not sure what. Unfortunately an Acura dealer is 4 hours away (San Antonio), but I may have to bite the bullet and drive up. Probably a sensor that measures engine load is being erratic and telling the converter it is OK to lock up, then changing its mind.

maybe if everyone is having the same "problem" its not really a problem?

I've noticed my TL does this and apparently after much of poking around on azine, it's been noted that the TL doesn't like being under 1500 RPM in 5th gear and can cause that fluctuation. I did notice though after getting my transmission fluid changed 2x, the fluctuations went from 200 RPM to almost none and it stays pretty constant.

I thought I would post back that cleaning the throttle body seemed to help by keeping the transmission from shifting into 5th gear too soon, but the rpm still bounces around if it does go to 5th. I'm guessing the erratic air flow was messing with the logic of the transmission controller and making it shift too soon. By cleaning the throttle body, I mean taking it completely off and cleaning both sides of the valve and the inside of the intake manifold (finger depth only). It is kind of a struggle to get the throttle body off since the intake is kind of stiff, but take off the 2 bolts & 2 nuts, disconnect the 2 coolant hoses and you can kind of wiggle it out, almost no coolant leaks out. This was the first throttle body I've seen with coolant flow - I guess the air flow sensor gets too hot otherwise. I plan on doing a tranny flush soon, maybe that is the best fix.

It's completely impossible for cleaning the throttle body to have any effect on how or when the trans shifts. 100% impossible. There is no mass air flow meter. The coolant lines are there to heat the throttle body in very cold climates to prevent ice from building up and sticking it. Most of us bypass the hot water.

Up-shifting an auto trans into too high of a gear too soon is a sure way to overheat the trans. If you're driving around in manual mode with the trans locked in 5th and you give it throttle and it can't downshift to 3rd or 4th, it will unlock the converter to try and get the rpms up and into the power band. Converter lock/unlock will become much more pronounced when the vehicle speed is low and you're in a higher gear. When the temps start rising, the trans tries to keep the converter locked as much as possible to bring temps down yet it has to unlock easier than normal because it can't downshift. The few times I drive mine in manual, I never go into 5th around town. It keeps temps down and with the converter locked in 4th, you're pushing about the same rpms as 5th with it unlocked while being more efficient and creating less heat.

This is user error. It might do it more in the summer because it's trying to keep the trans from overheating.

Same issue on my 2004 MDX
 

Would any of you who had experienced this issue let me know what happened in the end? Did the torque converter fail?

I'm having the same problem on my 2004 MDX. The RPM's fluctuate in 5th gear at a steady speed between 40-50 mph.

Thanks!

I got a 3x transmission flush and that solved the problem. About a year later it started again, so I did a 1x flush and solved it again. I think the trans is just really sensitive to slightly old fluid when you drive right near the 4-5 shift point. If your fluctuation is more than 2-300 rpm then it may be something more serious.