trickstar

Hi,

I'm a new owner of a used, salvage 05 tc with 73k miles on it. It was in an accident, and the left front corner was impacted. It's been repaired. It runs pretty well, but the tach lays all the way down near or at zero when it's at what seems to be a reasonable idle.

At other times, when I step on the clutch or brake, it seems to go to a rougher idle.

It feels that it might be a vacuum oriented problem. I've changed the spark plugs, and it seems to have helped a little bit. I also reattached a tube that seemed to be gathering fresh air from straight down to go into the cabin air intake compartments up near the dashboard/firewall.

I have to check and clean the throttle body to make sure that everything is moving freely.

There is also a short air intake that looks to be aftermarket, and it has a TRD exhaust on it.

I took off the short air intake to make sure that the check engine was working... it was working.

Are there any specifically vulnerable vacuum hoses that are particularly troublesome on these models? Any capillary tubes or hard plastic tubes that are vulnerable to rot or breakage?

Thanks, I'm thrilled to be a part of the Scion community. There just doesn't seem to be too much involvement here. I guess that I'm just more used to more stuff to fix on my old car that was not a Toyota.

Jimmy

skakemokid

iTrader: (1)

Hey man.. try clean the maf sensor.
My idle was cracked out before i cleaned it. And very sluggish

CDogbert

I'd definitely go after the usual-suspect MAF first, then I'd scrutinize all the vacuum lines and make sure they're happy.

Is there any noise out of the ordinary when you're at idle?

tcchris38

what do you clean the maf with?

engifineer

For the tach, if the idle seems normal and smooth and the needle is sitting near 0, then something is off. Is the gauge lighting something other than amber? If so Iwould suspect they did an led swap and didnt install the needle properly. If it is installed correctly then it should sit dead on 0 when the car is off. If not, let me know and I can tell you how to fix that.

Applying the brake can make the idle sound different, but if it is significantly rough, then I would suspect a vacuum leak. If the leak is bad enough you may be getting some sort of CEL relating to a lean condition. Any sort of abnormal hissing sound under the hood when the car is running?

engifineer

Buy some CRC MAF cleaner from the autoparts store. Take out the MAF and spray it off well with the cleaner and let it dry. Dont touch any part of the sensor element.

trickstar

Wow, thanks for all of your help, it is appreciated... I didn't know so many people kept such a close eye on this forum!!!

To start, let me clarify that there is no Check Engine light coming up while the engine is running. Only before starting, like it's supposed to.

There is a CRC MAF Sensor Cleaner available for cleaning this. I was just looking at the MAF today, wondering about it. It looked like it had a varnishy coating to it.

There are no out of the ordinary noises during idle, as far as I can tell. There is no hissing under the hood while running the engine.

I believe that the gauge color is still amber, one of the few things that the previous owners didn't try to mess with on this vehicle.

I just went outside and started it while completely cooled down. Before starting it, just turning the key to the position where all of the lights come on on the dash, the tach needle and all of the other gauges did their prestart max-out, and then the tach needle quickly settled to a place where it was pointed way below zero, approximately negative 150-200 rpm (if you were using the spacing and calibration of the rpm marks in the normal direction).

When I started the engine cold, the needle went up to about the 900 rpm range, and quickly came down a bit. After warming up for a couple of minutes, the needle went completely to zero. No rough idle, pretty smooth.

I tried to roughen the idle by pushing the brake pedal, changing the a/c vent mode control and operating anything that might be vacuum controlled. Nothing was really affecting the idle too much.

I would like to see any instructions that you might have for calibrating or just repositioning the needle. My assumption would be zeroing it out while not yet started, but I'll be looking for any experience and input that you have.

Thanks again for your help everyone,

Jimmy

CDogbert

http://www.youtube.com/watch?v=0snizRfVSkw

rangerryda

iTrader: (1)

Search the forum for LEDmod.com and it gives you a rundown of how to remove and disassemble your gauge cluster (very very easy). Once you have it apart, use two spoons to take the needle off by prying straight up. Replace needle at 3000 RPM position (roughly) and turn down towards 0 until you feel more resistance. Once you feel the resistance, you need to place it at the exact position as shown in the LEDmod.com posting. It should work fine after that unless the actual circuitry is screwed up (doubtful). Good luck!

trickstar

Awesome, I just corrected the tach needle calibration, and next I'm going to get some MAF cleaner.

Great instructions for removing the gauges and setting the needle on the LEDmod.com link

https://www.scionlife.com/forums/sho...d.php?t=129571

With the non-running engine putting the needle exactly at zero now, it's little rough around 600 rpm after the engine heats up, smooth at 750. The engine management seems to sense this and sends it up to 750, intuitively.

I expect that this will get even better with a clean MAF sensor. I'll report back.

Thanks for your help everyone, it's been a huge plus!

Jimmy

ack154

iTrader: (7)

Moved your post.... think this is where it goes.

rangerryda

iTrader: (1)

Glad it worked out. As far as the engine idling funny, it could be a dirty MAF, faulty MAF, vacuum leak, or bad spark plugs. Other than that, I don't think anything else could commonly go wrong that would effect the idle in such a way. Our coils are pretty stout from what I've seen and our ECU's are too smart for their own good lol.

gwtc

iTrader: (4)

Did you recently disconnect the battery? the car is running in learning mode, that will also give you a very rough low idle, don't know?....just checking.

trickstar

Hi everyone,

Thanks for your help! I did it all, pretty much... changed spark plugs, cleaned MAF with CRC MAF cleaner, checked for vacuum leaks, etc. But, the thing that really worked to smooth out the rough idle was cleaning out the inside of the throttle, I guess really the choke flap mostly, and where it touches the walls of the throttle cylinder body. Berryman's Throttle body cleaner and a soft toothbrush. I wiped the flat surfaces and walls with a paper towel, making sure not to let the choke tear any paper towel off.

Now, it's idling like a new Lexus... smooth as silk!

Don't let anyone tell you that the throttle body can't get that dirty in a short time! And it's just too easy to clean it out, why not just do it, right?

Thanks again!

Jimmy

rangerryda

iTrader: (1)

ack154

iTrader: (7)

I just wanted to bump this and show that the search does actually work. I've had a rough idle problem for quite a while. I was hoping it would fix itself when I put an oem intake back on. I've tried cleaning the maf plenty of times. Still crappy idle.

Did a search in Drivetrain & Power using the Search This Forum link in the upper right and searched just for rough idle and ended up in this thread.

Cleaning the inside of the throttle body made a HUGE difference. It was really gross in there. So much black junk (carbon buildup?). Guess that'll happen after 85k.

trickstar

Yeah, I'm back to a rough idle. I don't know if it's just common with the earlier tc's, but I'm still searching after a long time. A/C is on, idling at a traffic light. rough

I'm looking at the temperature sensors, because I don't have a temperature reading on my climate temperature gauge. (not engine temp, but the outside weather temp)

Jimmy