its because you guys are pressing your brakes or using your a/c or having a stereo system running... that's why the rpm is varying, the engine load is changing and you can see it more when you are in neutral

 

eeee, what about power steering?? same when u turn your wheel when not moving while in neutral. start your car, don't put the gear in and turn your wheel all the way to the left or the right, your RPM will go up. engine reving to compensate for that maybe?? or I SENSE NO MAKE?

 

exactly

 

cept i've noticed that it happens not when i'm in neutral, but while i'm in gear, riding the clutch (to a stop sign for example).

driving in 3rd; approaching stop sign; depress clutch, shift to 2nd and start braking; not all the time, but sometimes, the tach does jump up and down and i can hear the engine revvving itself.

I think it has something to do with the idle speed control unit or possible some kind of electricical interference. (maybe a bad ground or something) but either way, it shouldn't happen. Its putting unneccessary stress on the motor.

 

usually when you downshift the rpms should go up and it seems like the engine is revving... but that is just the transmission forcing the engine to spin at a higher speed

 

HUH?? ah, [in a 5 speed] the rpms don't rise unless/until you apply throttle. its not like you clutch, downshift, and the rpms automatically jump to the correct speed to match wheel speed. you have to match rev to wheel speed. in an AUTO the rpms will "jump" when the car downshifts. Not in manual.

the trannsmission does not dictate what engine speed the car should be at. Gearing limits speed in each gear, and you won't be able to catch a gear unless you have the flywheel spinning at the correct speed to match the tranny/clutch's rotational speed.

Are you talking about auto's mabye?...i hope.

 

oops, i thought we were talking auto here...

anyway, wouldnt the same principle apply to the 5spd? i know that motorcycle's do it hmm

 

no. auto and 5 speed tcs are really not comparable.

 

eh... i think you don't know what you are talking about...

if you are going 70mph and you drop a gear (auto OR 5spd) the rpms will of course shoot up... it doesn't make sense that it wouldnt

 

i know im not a tC owner but... my xA does this same thing. it idles at 500RPM and every now and then it goes up to 1000 then back down, then back up then it stops. as far as coasting, it drops to about 650 rpm then goes up to 1200 and stays there until i come to a complete stop or put it back into a gear

 

WRONG! [in a manual] If you are going 70 in 5th, clutch, shift to 4th, THE RPMS DO NOT GO UP ON THEIR OWN!!! YOU HAVE TO APPLY THROTTLE TO BRING THEM UP! r u serious? how could you not know that. have you EVER driven a manual car?

and that isn't even what WE are discussing...so please, if you don't know, then stop posting and taking up valuable room for people who actually HAVE a 5 speed and know about this situation.

thanks

 

it's not that they go up, they hang in there for a while. u thiunk they do because of the sound the engine makes while not in gear. easier to shift as the RPM don't drop as quick. well in 5spd anyways.

 

rpms "hang in there for a while" when your not on the throttle??? thats news to me. :D in a manual transmission, the ONLY WAY to keep rpms "hanging there" or constant, is to apply throttle--and even still, with our ECT/drive by wire, its very difficult to actually hold a constant rpm. This is why so many people just blip the throttle while downshifting, to bump the rpms up higher than the engage point, so they can settle back down as your letting the clutch out.


the engine makes the same sound regardless of whether or not you are in neutral or whatever gear you are in. secondly, i'm talking about rpms bouncing as i have the clutch depressed (disengaged) while IN GEAR, aka. riding the clutch to a stop sign or something.


actually, the lower the gear, the faster rpms drop. so downshifting causes the rpms to drop more quickly than they would in the higher gear.

sorry bud, but i could not make any sense of your post whatsoever. care to clarify any?

 

You guys are talking about different things than what this post was originally about. If you haven't had your tach needle bounce when you are cruising on the highway after you press the clutch then you don't know what we were talking about. It's not the case of the engine trying to compensate for anything, it's the ECU and it goes away after a while. It's not the same as when you start your car or turn the wheel or turn on the A/C, this is a significant rapid bounce. When you reset the ECU or haven't driven for a while that will happen.

 

^^^Exactly. That is what happens in my car. except it doesn't ONLY happen while hiway driving. but yeah, extended periods in a single gear usually. and it doesn't happen all the time. and yeah, it does stop after a few minutes.

there is an idle speed control unit that is "supposed to" keep the engine speed constant at idle when you are not applying throttle. my best theory is that there is some electrical interference that causes this signal to deviate.

yes, different from how the tach jumps when switching on heat/ac.

on a side note, i noticed sometimes that i can shift much more smoothly when the heat is on. isn't that weird. Seems like i don't have to fuss with the throttle as much for some reason.

 

sound familiar? :

https://www.scionlife.com/forums/vie...r=asc&&start=0

sounds like scion may have an idle speed control unit tsb on there hands....i mean, i'm sure they already know about it. now its just a matter of time waiting for that magic number of people who complain about it to be reached. Then they'll decide to do something about it.

 

Toyota incorporates this into alot of their vehicles. its an emmission thing that burns excess gasses along with ensuring a smooth shift. My truck was like this. as well as my mates is300.

 

I believe this is a repost but anyway, yes it's normal, tons of people see this. Mine bounces like crazy, sometime from 500 to 1500 rpm. and the weird thing is that it stops when i come to a complete stop. If i keep coasting even at 1 mph it will bounce like hell, but once i stop, it instantly goes back to smooth idle.

 

And to 1SXETC, you say its easier to shift with the heat on, i think i know why. The heater/ac makes the motor work harder to run (parasitic drag) This causes the engine to lose RPMs faster. with the heavy weight of the stock flywheel (18 or 19 lbs, i think) , momentum keeps it spinning at the same speed for a half second or so, (RPMs kinda hang there). When you shift the rpms are still too high causing rough shift. But they drop faster with the drag from the heater causing a smoother shift. I noticed the same thing with mine, i would have to wait at least a full second to release the clutch during shifting. But now i have a lightweight flywheel, and it's hell trying to drive with the heat on because now the rpms drop too fast.

Off topic i know but just trying to help them understand

 

my girlfriend told me about her tC doing this and i was riding with her over the summer and she popped it in neutral down a smooth hill, no stero installed (just stock) windows down (no a/c on) and her RPMs bounced a few times, i told her dealer about it and they kinda blew me off like i was making ____ up. seems more ppl have this issue