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Posted

I just bought a 2007 IS250 last week. Whenever i drive it and put my foot on the brake or even let off the accelerator the tach shoots up randomly 500 rpm and comes back down. It almost like the tach is floating. I took it to the dealer on monday they said the car is just downshifting. I am skeptical. Whenever i brake its almost that i'm fighting the engine power to brake the car. Are all IS like this. the engine shouldn't be reving when i put the foot on brake downshifting or not. Its almost like the engine is undisiplined. The jump is only a little bit. Can someone plse help me out.

Posted

Watch the display and see if it's actually shifting from one gear to another. Mine will downshift, but it's not so sudden and only when coasting below 40 MPH. On the highway it never does that. Mostly I'll notice it when coasting to a stoplight, but still it's smooth and not jerky or anything.

The downshifting actually helps the car slow down and it's not like the brake is fighting the engine. I never paid attention to the tach but I'll try to do that and see what happens. With downshifting the RPM is going to go up, but the car should still be slowing.

  • 2 weeks later...
Posted

I've watched the auto-downshifting a little closer. The tach maybe blips 300 to 500 RPM, which is to be expected when dropping down one gear. It's not jerky or anything, but just a little extra slowdown. It's programmed that way and sure isn't going to hurt anything. At most it's going to help reduce brake wear a little. Nothing to be concerned about.

It can be an advantage since if you need to accelerate again, the trans is already in a gear to give the best power situation.

Posted

It is normal. In fact, it is something I have really come to love about the IS. The auto trans will almost read your mind & up*BLEEP*f/downshft when you want it to if you learn its shift points and feather the throttle. It took a little getting used to because I have never driven another car that downshifts as aggressively as the IS, but as others have pointed out, using engine braking reduces brake wear and keeps you in the best gear for quick acceleration.

--SB

Posted

It is normal. In fact, it is something I have really come to love about the IS. The auto trans will almost read your mind & up*BLEEP*f/downshft when you want it to if you learn its shift points and feather the throttle. It took a little getting used to because I have never driven another car that downshifts as aggressively as the IS, but as others have pointed out, using engine braking reduces brake wear and keeps you in the best gear for quick acceleration.

--SB

I don't have much to add to this post, I just thought it was funny that the forum program bleeped you when you switched the F and the T in "shift"

Posted

It is normal. In fact, it is something I have really come to love about the IS. The auto trans will almost read your mind & up*BLEEP*f/downshft when you want it to if you learn its shift points and feather the throttle. It took a little getting used to because I have never driven another car that downshifts as aggressively as the IS, but as others have pointed out, using engine braking reduces brake wear and keeps you in the best gear for quick acceleration.

--SB

I don't have much to add to this post, I just thought it was funny that the forum program bleeped you when you switched the F and the T in "shift"

Yeah, up*BLEEP*f is kinda funny. :lol:

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