TheMocoMan

Hey gang,

I've searched this forum and have tried many of the things listed. Before I go into the problem let me give you a little history. My tC is a 2007 Auto with 75K miles on it. It's ALWAYS had a shi**y idle and shakes the whole darn car. I chalked it up to the engine mounts and it being a cheap a$$ car. When the A/C is on it shakes real bad. I usually just shift in to neutral (even though it's an auto) just to stop the rattling of the trunk, etc.

Despite all this I still love her. Despite her being an auto I still put a TRD CAI and TRD axel-back back in February. I had the Toyota dealer install these parts and so far it's been good. No CEL's or anything. No performance upgrade really either. Lately though the idle has been acting funny, like it's having trouble breathing. When I start the car I have to hold the ignition a little longer than previous just to get the engine to kick over. The exhaust tip is rather sooty too. Is that a sign I'm running too rich?

Recently I had new spark plugs put in (roughly 2 months ago) I just changed my oil on Sunday with Royal Purple and installed the TRD oil filter. I also added some fuel injector cleaner to the current tank I'm on.

Per this forum I decided to clean the MAF sensor. I also (about 3 hours ago) pulled the #20 fuse for the ECU to clear the computer. I drove it gently for 20 minutes so it could re-learn or whatever.

Outside of all these things. Is there anything else I can check? Any advice? Give it a few days? replace the engine mounts for the shakes? If I'm too rich will this ECU reset hopefully cure this?

Also the engine itself. Well it sounds like a tractor motor. Doesn't really purr or anything. Maybe I'm just paranoid.

/end rant

my06tc

iTrader: (2)

run the car with the maf sensor unplug,and if the car stalls you know its good,but if it doesnt do anything its bad,

pyroman131

On a related segue here, typically when you have to hold the ignition down longer to get the car to turn over, your battery or starter might be on its last leg. Get your battery and starter tested to make sure they're okay, too. I'm taking my knowledge from the old carburetor cars I used to work on, so I imagine it's the same for new cars, too.


I know exactly what you mean. My xB2 has always had such a horrible idle and shakes like hell, too. Sometimes when I'm slowing down the idle shakes the car as I'm coming to a stop. It's frustrating as hell. I like the FR-S, but I really feel like this will be my last Scion.

TurboMonkey36

Spark plugs iridium and gapped to oem spec? If so, I guess it's just getting old. The auto tCs shake plenty more than the manuals when in drive. It's just the way Toyota made the motor more efficient by gaping all moving parts further apart; lowers friction, but makes it run less smooth. Mine at 44,000 is starting to idle more rough, though a manual.

TurboMonkey36

It could slightly maybe be the rings wearing down sippng in a tiny amount of oil over so many revs which explains the soot. Though that's probably normal considering a 75.000 mile tC.

Your engine mounts become loose over time, not sure if yours are cracked or loose though. Easier steps below.

Do you have a clean air filter? You can try clean your throttle body, that might help.

why87

probably plugs and wires and cap

aen

this is not too good advice. i've driven the tc without a maf sensor for a while. especially when it's boosted.

it's one of three things:

fuel problem
spark problem
air problem

we can narrow down from those three, fortunately none of those are really that serious for this strong strong block.

1.get a fuel pressure test if it reads steady at idle you're okay, give it gas, drive a bit, does it shoot all over like crazy? if it does, your pump might be out.

2. you would have a cel if you were misfiring due to sparkplug gap or anything like that. but test them check them and mreasure them. if i recall correctly the plugs the tc uses are pregapped and should not be regapped

3. do a air leak test. pressurise the system and listen for air. (i've done this a couple times)

sciontc_mich

hey mocoman! have you looked at the throttle body? I had an issue that there was a bit of sputtering going on at idle, sort of like a small amount of up-down rpms. This turned out to be the throttle body plate/throat area being gummed up with crankcase vapors, replaced the pcv it's been a lot cleaner. But I did have to clean the throttle plate and never had the issue again. Might want to check those two things. And yes it could be the engine mounts as well! But dont disconnect the maf sensor, that'll just throw a check engine light and it'll run in limp mode. not that you might have been considering it.

keep us posted!

torqueTc

iTrader: (11)

Exactly.. Replace your plug(s) if they are bad. I had one that had a minor bit of corrosion on the porcelain, and the car was misfiring occasionally. Idle fluctuated a little, car ran a little poor. My plugs only had 18k miles or so and one was bad. Toyota replaced it under warranty for me.

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 AC 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 repost this around since it was such a idiotic revelation.

Scion TC 2006 stock.

deez

iTrader: (4)

IAC Valve or Idle Air Control Valve.

deez

iTrader: (4)

Oh wait, Actually I don't think our cars have them. I think thats all controlled in our ECU.. hmmm

Spicy_McHaggiz

iTrader: (1)

+10 even though this isn't a distrubtor style ignition.

aen

did you ever check fuel pump?

TurboMonkey36

Any progress? Throttle body cleaner a rag and a screw driver is the simpliest fix. I'm leaning most to that's the problem. It only takes a minute. No Idle air control valve in tC, so gunk around plate edges make a better seal or raise friction/lower volume and ecm fails to open throttle often in that situation.

(If you take MAF off and it runs the same it might not say much, but certainly doesn't mean MAF is bad, just points toward dirty throttle body)

TurboMonkey36

Just some extra infos.....Oh, if it was fuel pump car would lean out at higher speeds knock, lose power, or misfire. Not likely the problem.

Yes, long time of rough idle due to dirty throttle body means running rich and soot build up, but not likely that's the reason, don't know the problem. If checking idle fuel trim, you could see that it tries to lean out on closed loop due to feedback, or not do anything to keep minimum fuel to keep engine running.

TheMocoMan

Well the car runs smooth like a champ. Can't complain about that. Just when I pull up to a stop light, some days are better than others. It just VIBRATES a lot. The motor itself is rockin like a tractor and shakes the whole car.

I moved last weekend so I haven't had free time. But I'll give the throttle body a good cleaning. Got a YouTube video for that by chance?
or a link on this forum with pics?

Thanks Forum for all your tips.

TurboMonkey36

Don't count on it, but I might do a quick clean of a tC's TB and make a simple write up later today if I have any throttle body cleaner left. No problem man, just figured I should help if I can.

mxyooji

I don't have a rough idle but similar problem. Very shaky car when the a/c is on and I am just idling. Rpms are at about 700 and not fluxuating up and down.

My car is 05 tc manual with 125k miles so I'm leaning more towards the bushings and mounts...

Sent from my I727 rocket on Marz! @_@

CSOCSO

iTrader: (1)

I still have bad idle. And reset the ecu several times. Bought pre gapped denso spark plugs. MAF is clean. Did a seafoam treatment .Only major mod is cai and exhaust