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Scion tC 1G Drivetrain & Power Engine and transmission discussions...

RPM's bouncing up and down ?

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Old 11-12-2007, 05:32 AM
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Originally Posted by ppiech2
I've been meaning to post this for a while cause mine does the same thing. Glad to hear I'm not the only one!!!
X2
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Old 11-12-2007, 12:59 PM
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Originally Posted by datrickster24
IAC valve..
You think its the idle air control valve? In so many cars is that possible.
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Old 11-12-2007, 02:35 PM
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If you are still under warranty, have it checked for free. Sorry, I had to say it :D
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Old 11-12-2007, 03:58 PM
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can you hear the change in RPM or is it just the gauge
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Old 11-12-2007, 04:19 PM
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Yes you can hear it and feel it. Something like this problem the dealer will look right at all the mods you did and tell you that is the problem. So the dealer ship is out of the question for this kind of problem.
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Old 11-13-2007, 07:10 AM
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i didnt think our cars have an IAC due to the drive by wire, the ecu controls the idle.
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Old 11-18-2007, 11:42 AM
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my RPMs flick upwards when i coast down the off ramp from the freeway as well!!

i see it flick up and i hear like my exhaust or like a fluid pumping noise -.-

freaks me out :/
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Old 11-19-2007, 04:10 PM
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ive had my tc for like 6 months so far and this problem just started happening...like ^^^ my rpms drop all the way down to the 5's and go back up to the mid 1k...the problem im having is that it does it a few times until i get off the clutch again. i live in cali so it does it whether its hot or cold...and it happens when im in traffic or cruisin at 70...soooo idk wtf is up....
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Old 11-19-2007, 08:58 PM
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i got it also, seems normal. i never had a problem from it yet, its prolly the maf reading more air and trying to dump fuel but its getting confused because of the throttle position.
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Old 11-20-2007, 02:26 AM
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sorry just need confirmation

1. so 05-06 engines have a rev limiter that makes the needle bounce off the red line. 07-08 have a fuel cut off valve that cuts the fuel to the engine when exceeding red line, but does not have the need bounce
2. it is normal to have your rpms go up when you put it in neutral and you are coasting on the freeway
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Old 11-21-2007, 09:41 AM
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whew
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Old 11-24-2007, 03:42 AM
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mine does the same thing... ill get on the clutch, the rpms will drop to a little below idle, and then bounce to a little above it before settling in at normal. i'm guessing it's something most of us experience and is not an issue. i'm not stock anymore, but it would bounce just the same when i was stock.
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Old 11-27-2007, 02:24 PM
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This is kind of a late response but if anyone is still watching, mine does the same thing. Except my car idles at 500rpm when warmed up. Is that normal? It use to idle closer to 800rpm until I put on headers.
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Old 11-27-2007, 08:06 PM
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ooooo 500? i think thats a lill too low....mine stays at 700-800....with header back....i think u shud check for leaks...doesnt it feels like its gon stall?
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Old 11-27-2007, 09:34 PM
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I don't believe there are any leaks. It doesn't have a loud noise coming from anywhere unusual. I have a feeling it might be that my rpm guage is off a bit. I remember it going lower right around the time I did the LED swap. Do you know if the rpm gauge adjusts itself?
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Old 11-30-2007, 02:30 AM
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Wow 500, Does it feel like it will stall? im curious. and add me on the list of the needle going up. I noticed this especially right after i put in the brothers lightweight crank pulley. But there are people saying that they have this in a stock TC? then phew i feel better maybe i just dint notice before.
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Old 11-30-2007, 09:04 PM
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phew, good to know im not the only one out there, and i was always afraid to go to the dealer too cause of the amount of work done to the engine, and their easiness to blame everything ona mod... but mine does it when im coasting or coming down a high speed, roughly from about 50-ish, and drop into neutral and then i see the revs drop to about 600 then bounce up to 1300-1400 and repeat several times until i slow down to a crawl or put back into gear... if anyone can think of a reason... maybe a leak or for alot of us, a common mod that somehow caused it?
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Old 12-01-2007, 12:53 AM
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Cant be a mod some of people on page 1 i think said they have too with a stock tC. My car is only about 4k miles so if itz a leak then omg itz another problem that just makes toyota look bad.
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Old 12-03-2007, 02:02 AM
  #39  
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my cars been doing it for 3 years with and with out mod its going to happen sorry and the more stuff u add it gets worse. U will be fine man
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Old 12-03-2007, 04:19 AM
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Yeah it just sucks. I mean 16k is still alot of money and ijust wished toyota fixed the small things. Like hatch rattle. Even if things are covered under warranty i shuldnt have to go back to the dealer to waste my time. But thats another story. Good to know i dint break anything.
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