Xander2011

I bought my tC2 in March 2011 and noticed that at red lights and stop signs, my RPMs sometimes go lower than 500 causing the car to have a rough idle then it stops when they go back above 500rpm. I took it the the dealer when it was due for its 5000 mile service and said that they cleaned
out the overhead, which I thought was dumb for it being a BRAND NEW CAR, and was told the gas i was using from the gas stations that i use which is Valero is bad. I've never had a problem with any vehicles with this using the same fuel. I now have about 9245 miles on it and it STILL does it.

Curious if anyone else is have this problem? The car doesn't do it all the time but it still does it a little too much.

Thanks!

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KyleG

Your not the only one, my tC2 does this as well. It seems to have a mind of its own idle wise, on a hot day starting up with the A/C on its around 2k,
then as you say sitting at a light with the A/C off and the engine warmed up it can drop to around 450 rpm.

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Xander2011

I'm glad I'm not the only one. Have you tried anything to try and stop the RPMs from going below 500? And have they worked?

brushlessdavid

i have the manual u guys with the rough idle all have automatic??

tribestros

I took it in, but the car wouldn't reproduce it again, so I don't care.

donsun

i have a manual, it still does the idle fluctuation once in a while when idling and i also get rough start ups once in a while as well..

Krayzie_Los

I had this problem with my 05 tC 5speed, always used 91 Chevron, but multiple stations, usually was random but the worst after disconnecting the battery.
Cleaned throttle plate, replaced MAF sensor, cleaned air filter, still rough idle at lights and had to heal toe whenever sitting at a stop. No codes and never figured out what it was.

Now I have a 2012 tC and I was hoping this problem was fixed, but after reading this I am concerned...blah

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Blackedout011TC

iTrader: (2)

A few ways I have fixed this problem on other imports. Tiny cracks in vaccum lines. Cleaning MAF sensor. The last thing I can think to do is check the idle adj. screw on the throttle body intake. You'll need to pull the entire air box hose out to verify you are on the right screw that opens the intake butterfly valve. Make a very smal adj. Some are a counter clockwise turn to open the idle gap. All are a pain to get to as they are usually close to the firewall. Also this adj. screw has an O-ring in some cases which could be leaking.

Xander2011

Thanks Blackedout011TC. I will plan on doing this on my tC. Awhile back, i started using the 91 octane from the Valeros but the idling and MPG all stayed the same so I just stayed with the regular fuel. I have also notice that when i do "spirited driving" the idling starts to drop below 500 rpm at almost EVERY stop.

Scratch

iTrader: (3)

Do you have any modifications to the intake, or any other significant modifications to the car itself?

fun173

I have noticed mine does this too. 2012 RS7 bone stock.

krytikel

My 2011 does it too. I noticed it big time when I first disconnected the battery to install my sub. Then it kinda evened out but it still fluctuates between 450-500 RPM's at the light. Thought it was just me but I guess not .

wanathon

Eventually I'll get to how I fixed rough idle at a stop, but the story is kind of important too...

I was having serious problems starting the engine with only 35k miles. It would take multiple consecutive cranks to initiate the engine. There was also a rough idle. I brought it to Firestone and they thought it ran fine but did a fuel injector cleaning anyway. It still had issues.
I bought a new battery and installed it. Only then did I realize that the Progressive Snapshot device I had installed was setting off the fuel-cut off security system and messing up the fuel intake somehow. After I took it out, the car started fine, but the rough idle was still there.

A year later, I realized that when I changed the battery and had cleared out the ECU (I am not car-fluent), I did not properly RESET the ECU. I was suppose to LET THE ENGINE IDLE for 5-10 MINUTES! That's all I had to do! Everything runs normal now
(except for the stupid noises coming from the hatch and minor A/C rattle )

So, when you change or disconnect the battery, be sure that the first time you start the engine you let your car sit and idle for 5-10 minutes. The computer has to learn the new idle. Sorry if this is obvious to everyone else on this board, but I had no clue.
I mean the manual says not to let your car idle when you warm up the engine. Before you look at your throttle body, spark plugs, engine mounts, or whatever, be sure you've done this, especially when you don't have 100k miles or more.

Good luck. Hopefully it's as simple as my solution was. I'm going to Re-post this around since it was such an idiotic revelation.

2006 Scion tC stock.

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TwztedtC

My car will occasionally dip down to 350 rpm but only sometimes

Sent from my PC36100 using Tapatalk 2

clickclickw00t

Hey guys I'm having the same problem!!!

2012 tC2 Automatic. Have had it for exactly 1 year as of today. 12k miles on the ODO.

Pretty much EVERY TIME I stop at a red light, I get an RPM drop. Usually somewhere down to 450-550 rpm. I get an AWFUL vibration. I really really hate it. If I pop the car into neutral, it does the same thing. I took it to the dealership for the second time today, and they told me there was
no error codes and they couldn't do anything about it. After talking to the manager, they cleaned out my throttle body. That did nothing. I still get vibrations in Drive and in Reverse when I am stopped and on the brake. I pay good money for this car and it should work like any other car.

Has anyone gotten a direct answer from Toyota for this? It seems unreasonable to have a 1 year old, BRAND new car, and to have it do this. I've had the problem since day 1 that I've had it, and its only gotten worst. Has anybody gotten around to fixing it or making it less annoying?

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BrokenTusk

My 2007 Toyota Tacoma Idled at 900 Rpms and dropped down to 650-ish rpms every few seconds. Did that the entire time I owned the vehicle. I was told it was a fuel saving function.

I have a 2013 tC RS8.0 (6-spd Manual) and it Idles at 700 and drops to 400ish when stopped at lights. It's done this all week that I've had it, and if I mash on the throttle it picks up
and goes so I haven't had an issue with it. I'm pretty certain this is a fuel saving function in the ECU programming.

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clickclickw00t

yea but does it have to vibrate so much? It almost feels like the car is about to stall... It's the same feeling you get when you drive a stick shift car and you don't give enough gas when releasing the clutch. It gets worst and worst every day. I didn't lease a brand new car for it to feel like its dying everytime I stop at a red light. Fuel saver or not, it feels absolutely terrible. As soon as I put the car into neutral I get NO VIBRATION at all. If I have the A/C on, I get very little vibration. only when the A/C is off does the RPM drop down to 500 and feel like its about to stall. Something tells me its a problem with the transmission.

I did some experimenting and when I my foot on the brakes it is the worst. If I let go of the brake and engage the hand brake, the RPMs go up slightly, and I get less shaking. If I put the car in netural, no shaking.

BrokenTusk

In gear or in neutral I get no shaking. I'm unsure what your refering to.

clickclickw00t

In gear (Reverse, Drive) and stopped with foot on brake and a/c/ off : car shakes with RPM hovering around 500rpm
In neutral with a/c/ off: no shaking

in gear with a/c/ on: little bit of shaking but not much

When the car is cold and warming up, the RPM is steady at about 750-1000 RPM and no ABSOLUTELY no shaking in gear. AS soon as I've been driving for 10 minutes and the car warms up, shakes.

SJA4444

I have the same issue as well. [RS7]. Car was fine initially. Has gotten progressively worse as well. Completely agree with the "shaking" description. The engine is just idling way too low and rough for my comfort. It is that same sensation you get right before a stall out or like when you almost run out of gas in an engine. At next Scion checkup plan on bringing this up
Of note, this same issue ( I believe) caused me to send back my AEM CAI, as the car would actually stall out on occasion as the RPMs dropped too low.
Its completely annoying, I have no idea why they have the car set to idle that low, and why the A:F ratios seem to be sooooo tight and picky