wazlo21

I made a post a little while ago about the noise my car makes when making sharp turns and as I was taking another look through the threads, a second issue popped to mind. My car knowledge is pretty close to 0, so I may not be using the right terminology/descriptions, so please bear with me.

I have an '05 TSX AT. Sometimes when the car goes over the peak of a hill and starts descending, the engine races/doesn't downshift as it goes downhill. The car will stay at about 3000 rpm all the way down the hill and doesn't downshift (rpms go down) until the road flattens out and I step on the gas. Neither braking nor stepping on the gas while going downhill affects the revving/racing.

Any thoughts on what might be causing it to do this?

LuvMyTSX

Sounds like the grade logic control feature. It's normal, if this is in fact what is happening. It's just holding the gear for you.

jlukja

^^ Luv's right. The terminology needs a little work though. "downshift" means the transmission is shifted to a lower gear (rpms go up). "Upshift" means the transmission is shifted to a higher gear (rpms go down).

The grade logic feature will hold the gear that you are in while descending a hill so as to not allow the speed of the car to build up on the descent. It takes advantage of the car's ability to engine brake at higher rpms.

Also, if you want to bypass this feature you can do so manually by moving the gear lever into Sport Shift mode and then manually downshifting or upshifting as you desire.

ThirdLane

Downshifting during a descent with actually raise the revs of the car slowing the car down even more/faster. Upshifting will lower the revs but you won't be able to take advantage of engine braking and actually speed up down the hill.

wazlo21

Thanks for the info guys. I didn't realize that engine braking was a good thing. I was always a little concerned when it did it and I'm glad its not something I have to worry about.

Also, thanks for the clarification on the terminology. I can use all the help I can get.

Lastly, I really appreciate the time everyone takes to help out on this site. It is good to know that I can find advice without worrying about someone talking down to me for not having advanced knowledge of the inner workings of a car. Heck, if I had that, I wouldn't need to be here.

davidspalding

Engine braking ... did it for years with my Jeep (it's a 4WD technique, to resist losing momentum in the muck, and keep torque high) ... but I recall someone (Car Talk guys?) saying that an engine and a transmission are more expensive to replace/service than brakes ... and let that help you decide whether to downshift, or just judiciously use the brakes. (Granted, using the brakes disengages cruise control. I do indeed like how the grade logic works on downhills on the freeway, keeping me from exceeding the speed limit more than 5-6 MPH.)

muncher

Also, don't forget that when you engine brake, your brake lights don't come on, so if you're going down a really steep hill, I would recommend not engine braking because some drowsy trucker behind you might not notice you're slowing down until it's too late and bulldoze you off the side of a cliff.

xenonhid

Yup, gotta love the GRADE LOGIC Feature.

It worked like a charm when Seattle got some snow a year ago while going down a incline.