I was driving my new TL-S (1800 miles so far) home from work today. I noticed it would shake a bit when I was going somwhere between 15-40 MPH.

It initially gave me that shaking feeling that you get when a rough idling engine is about to stall and is rocking in its mounts. But the engine sounds like it is running fine, I don't hear a misfire or anything. I can't really isolate what the prob is. Also it seemed to go away under acceleration.

I'm figuring it could be from one of 3 places.

engine running rough:
doubtfull since it aprears fine and holds a nice constant rpm w/ constant accelerator on level ground.

trans/torque converter:
maybe my trans is failing? I did a quick search on trans problems and it sounded like most people experiencing problems had major catastrophic failures with dash lights flashing and barley being able to drive. I guess it could just be the tourqe converter locking/unlocking at that particular speed as well.

shocks:
I guess I could have just found the cars resonant frequency and it just started oscillating a bit.

I really didn't have too long to play around and try to isolate this, traffic was heavy for a bit so I couldn't vary my speed much, then all of sudden the traffic broke up and I was doing 80 and the ride was nice and smooth again.

Just wondering if anyone had experienced similar problems or had any suggestions. Perhaps I'm just being overly critical since I just spent of $30k on my first new car.

I'll guess I'll see what happens on my way to work tommorow....

 

My car kind of has a weird habit every once in a while. Every once in a while during low/mid-speed driving the RPMs will drop for a split second...it almost feels like it's hunting for a different gear. HOWEVER, it does this even when I'm using SS, so I know that's not the case. The symptom happens when I'm cruising along at a constant speed. Is that at all similar to your symptoms?

Does anyone know...

Could it be the torque converter? What exactly does the torque converter do? Can someone explain? Thanks.

 

http://www.howstuffworks.com/torque-converter.htm

 

Great website... I've bookmarked it for lots of great "layman" information on all sorts of topics.
Thanks for taking the time to post the link and pass on a great resource. Southbound

 

mine does it too with the tranny while cruising at 50mph - it feels like a momentary loss of power.

 

That's about the speed mine does it at...somewhere between 40-50 mph.

 

Whatever it is, i is really annoying.

Some cars have a tranny "thump" when slowing down to a complete stop, somewhere at 5mph. When I used to have it with other cars I got used to that.

Having a "loss of power" sensation at 50mph is really hard to get used to. Plus having to explain to passengers that nothing is wrong, the car just does that. They would probably say "well, then your car is crap!".

 

It sounds to me like that is when the torque converter is locking up. If so, this is normal. It's when the computer decides the car is up to cruising speed and that there is enough engine power to solidly engage the engine to the trans via the torque converter lockup clutch. It does this to slow the engine down, reduce trans heat, and increase mileage. See the italicized info below.

On most cars (I'll have to check my S) this happens around 45 mph. It will be acompanied by a a slight decrease in RPMs on the tach. This can feel like a slight loss of power because the engine cannot rev as freely as it did prior to lockup.

Per the "How stuff works" article:
At higher speeds, the transmission catches up to the engine, eventually moving at almost the same speed. Ideally, though, the transmission would move at exactly the same speed as the engine, because this difference in speed wastes power. This is part of the reason why cars with automatic transmissions get worse gas mileage than cars with manual transmissions.

To counter this effect, some cars have a torque converter with a lockup clutch. When the two halves of the torque converter get up to speed, this clutch locks them together, eliminating the slippage and improving efficiency.


Now as far as the original question goes, I would visit the dealer.

 

I realize this is a really old thread, but figured I would resurrect it since it describes an occasional random issue I have. I have mentioned it before on another thread but there are some posts here that describe this issue identically to mine. I have an '02 type S with 174k. Only seemed to occur within the first 5 miles of driving. Sometimes even if I only parked the car an hr and got back in. I get a real quick studder, jerk, etc at around 40mph and I have had the car in SS mode a couple of times when it happened. The car isn't downshifting but I believe it is the torque converter quickly releasing and then engaging again. It is very noticeable when it happens. Maybe the grade logic although it typically occurs on flat ground at low rpm cruising speed.
Just curious if anyone else experiences this?

 

I've noticed some jerkiness while driving but setting it to D4 instead of D5 seems to alleviate the problem.

There's something in the owners manual about it..

"D4 can also keep the transmission from cycling between fourth and fifth gears in stop-and-go driving"

 

Yeah I do that too sometimes. Seems like if you are in D5 (but car is in 4th) and drop it into D4, the rpms seem to jump up slightly- maybe a few hundred rpms.

 

Try driving in D4 consistently and see if you still notice the problem, switch it to D5 if your getting onto the highway.

 

Might try checking the vacuum lines to your front & rear motor mounts. If they get a leak in them, it will cause a little stumble every now & then.

 

True- I think I'll be finally attempting my rear mount this weekend so I'll see what I find

 

^^^ Should ya decide to tackle that dreaded rear motor mount......take a few pics and notes
along the way......if ya think about it, while taking a breather for your sanity. Good Luck !!!

 

I believe the same thing is happening to me. All shifts seem perfectly smooth, but going at a steady speed it feels like something is engaging/disengaging and the RPMs go up and down while this is happening. It will go back and forth many times, like it's trying to engage but can't fully stay there.

Are there any ways to diagnose this? I was thinking of disconnecting the torque converter clutch solenoid connector to see if the problem goes away. Is this solenoid easy to remove? From the diagram it looks buried under a bunch of stuff. I haven't had a chance to look at it in person yet. Temperatures have been mid-20's here so I haven't spent any time outside when I don't have to

 

Although I every so often still get a sudden quick studder within the first 5 miles of driving, it is very limited. The shuddering I had at low speeds/low rpms has been eliminated with lubegard red