Setiri

Guys, we've been over this topic at least once before, just use the search feature.

Yes, when you're doing say 70mph and you push in the clutch, your RPM's will actually hang for a second in a tC (as opposed to many others you may be thinking of). This is purposefully done to allow for smoother shifting.

Ex. Person is doing 50mph in 4th gear at 3,000 RPM, they push in the clutch and shift into 5th, the RPM's have hung for a second at 3,000 and now the driver begins to let off the clutch. By now the RPM's are probably closer to the 2,300 range that the engine would forcefully (due to engine load) bring them down to and thus the "shift" seems smoother overall.

Now, that's 1 issue, I realize some of you are talking about the other issue. Again doing 70mph in 5th, approx 3,000 RPM. You press in the clutch and coast for a bit. The RPM's fall after that initial hang of about 1-2 seconds and bottom at 900 RPM or so... then suddenly they jump a few hundred RPM and fall back to 900 RPM shortly thereafter, as if you gave the throttle a little burst.

Why does it do this? Could be that the engine is running too low on RPM's to supply the alternator with enough juice due to a heavy load from the radio/ac/heater/etc. Or it could be that there's a legit reason for it, we simply haven't discovered it. Very possible I would say.

Worst case scenario, something is actually wrong. In which case I'd fully endorse you taking it in and getting it checked up while under warranty and report back to us.

TC-N-Philly

so many uninformed people when it comes to leaving your car in gear. It is not illegal to coast in neutral whether it be in an auto or manual. It is however somewhat illegal to downshift if you don't have your foot on the brake. The reason being is that the person behind you has no idea you are slowing down because your brake lights never come on. Will you get pulled over for it? Probably not... Can you be held liable if someone rear ends you? absolutely.. I've seen it hold up in court (I used to be a cop). So be very careful when downshifting into red lights.

tCizzler

^^^Sorry but you're wrong, it is illegal to coast in neutral. Not when coming to a stop, but just coasting to coast,yes. I come from a family of cops too, sheriffs and constables. Maybe laws are different in different states, but we're pretty close here in the burgh, and you in philly

jiggadomino

finally found out why it does it!

Dkfung88

wow i kept reading and all i see is people talking about putting the car in neutral and coasting down the road which is completely irrelevant to what the topic is about...

but to answer your question, i notice that in my car as well.. i heard the computer needs to readjust the idle rpm and to reset how much fuel/air it takes in at a certain rpm because of mods in the car.

Mikeydizzle

mine will jump rpms when i push in the clutch. only about 500 but it definitely jumps slightly. but this happens every time i push in the clutch... maybe some sort of rev matching?

jiggadomino

isn't the topic about the rpm's bouncing up when you are coasting on a highway and you put it into neutral for manual transmissions?

my car did this when it was completely bone stock, so it is not because of mods in the car.

bigwillystyle23

mine does it when its cold

TC-N-Philly

I should have been more specific. I was a police officer in MD. The law applied to larger vehicles when coasting to a stop. The reason; coasting in neutral, or with the clutch depressed, is potentially dangerous because you have no engine braking, and can't suddenly accelerate out of danger if need be.

jiggadomino

^ wonder how you'd enforce that; but its cool that you were a cop back in the day. Were you traffic or something else?

WAlterEgo

iTrader: (1)

ive been looking at the dates and i realized that this is an oooolld thread.

jjp735i

I had to chime in because mine 05 tC started doing this yesterday. I have 35,000 miles. It's going to the dealer for some other work so I'm going to ask the tech.
This is not normal in a manual. Driven manuals for 27 years and never had any of them do this. Mine started bouncing when I'm stoped, even if the clutch in or not, bounces from 600 to 1500 until I start moving again. I have to agree with whoever posted the vacumn leak. That's what I think it is too. Will post what the tech says when I take it in on the 16th.

jjp

jiggadomino

really?
my 07 has done this ever since I got it from the dealer; brand new.

Menace

Its the ECU not the tranny it self thats causing this. If everyone resets their ECU then goes on the highway, and swings the gear into neutral, every tc owner will experience this. The ECU is determining correct idling, etc...

TC-N-Philly

Only did patrol.. Traffic takes a few years to get into in certain departments. Usually comes with a pay raise and more responsibility. I could still pull traffic for basic offenses, but traffic guys can operate radar, reconstruct accident scenes etc.

In terms of enforcing the coasting law, I can honestly say that I never pulled anyone over for it. But if you are driving next to a larger vehicle, it almost sounds like the driver kills the engine when coming to a red light. Normal breaking comes with some engine noise and engine breaking or downshifting comes with a lot of noise. That's the only way I can describe it?