Is it when the engine is cold or just temperature overall? Does it ago away once the engine gets to optimal temperature?

 

When the engine is warm. I have searched the internet high and low for a solution. No one seems to ever fix it on the 2003-2004.

 

What kind of oil do you use?

 

Synthetic 5w20 Pennzoil Platinum.

 

Does it burn much oil? Have you tried better gas, ethanol free if available?

http://pure-gas.org/

What do you mean by a "rough" idle though? Does it sound like it's running on 3 cylinders, does the idle speed fluctuate, does it vibrate from idling too low, or does it idle too fast?

 

Doesn't burn a drop. Use only Shell fuel. I have tried Shell V-Power with little to no improvement.It is more like shudder in park with it vibrating badly when cold when in drive and the engine rpms drop down to 600rpms.


But 600rpms doesn't shake as much when the temp is -10c vs -20c.

 

OK, so the engine runs fine, it's just transferring more vibrations while idling in drive when colder out? How cold is it there? Mounts do get stiffer when colder, but maybe your upper right isolator mount is bad.

It's time to change all of your original ATF, by the way.

 

How did you clean the idle air control valve?

600 RPM will cause most cars to vibrate. The question is why is it going down to 600 RPM.

Can you monitor engine parameters when the issue happens and post them?

 

Go ahead and check your vacuum line, the hose going into the back of the manifold. That will cause it to shake. In fact, when I replaced my intake gasket, that hose was slipping back for some reason. I put a hose clamp on it and it stays on.

Yes, it did make my rpm go down to 500-600 and shook badly.

 

So, your car idles at 600 all the time or just when it is real cold. If it is idling at 600 it will have a rough idle. Sounds like a leaking vacuum line like Asheville stated.

 

It has done it since I bought in in October. I have checked all the vacuum lines and they are all on tight. When I am driving for 45minutes to work in -15c or colder, when I park the engine will be shuddering quite a bit. The warmer it gets, in park it doesn't shudder at all.


Turning on the headlights will allow it to idle up a bit more, but electrical load will have it idling rougher. I am wondering if the cold weather might be dropping the battery temperature down and putting more electrical load on the alternator,


The IAC doesn't seem to be the issue seeing it will idle up with the A/C and if I turn the steering wheel.


It seems to be a problem with the 2003 and 2004s a lot of the time and no one seems to know how to fix it seeing it is throttle by wire.

 

2003 and 2004 actually have a cable actuated throttle. Drive by wire is found on 2005 and up, which are the ones with the common low idle speed problem. My 2004 still idles perfectly, as always.

Is your idle down to 600 rpm only when in drive? What's your idle speed in neutral or park?

 

Sorry, thats what I meant. The low idle failures are usually associated with the 2003 and 2004 through research with no real solution found.

The idle is 600 in drive and when really cold out idles that low in park or neutral.

When coming to a stop it it will be at 750 and then drop to 600 or so after 3 to 5 seconds like it is idling down.

 

No. Like I said, low idle speed problems are related to 2005+ with DBW, and NOT 2003 and 2004.

 

Does it stay @ 600 or gradually recover? Mine does that sometimes, but not very often.

 

If it sits idling and warms up it will recover and idle relatively smoothly. Its almost like the engine is running too cold or something is not liking the cold.

 

Odd. Sorry couldn't help ya.

 

Have the same problem for years never found the culprit

New VSV Valve, intake gasket. New IAC new maf new pcv clean throttle body loads of time new tps new plugs o2 sensors and loads of other sensors never made any difference it's a mystery a big head melter do toyota even know what the cause is.

 

What year is yours?

 

2005 saloon some people get lucky just changing the intake gasket but the corollas are knowing for having rough idles.

 

Yup I've just accepted it as "nature of the beast".

I threw some cheap motor mounts in it a couple years ago which made a HUGE difference in idle quality, however it seems to be especially rough this winter. The weather is much warmer today (almost 70f) and it idles much, much better now.

Ultimately I may end up putting in genuine toyota motor mounts and adjusting the valves (which is a real pita on these) but as long as it's not setting any codes and the fuel economy isn't suffering I'm not going to worry about it.

 

Yea, the automatics are even worse. My mother in laws 5 speed 2007 idles great and higher than my car. I am going to probably get a 5 speed seeing that is what I wanted anyways.


I can't beat the economy on mine though. It gets 600-620kms per tank in -10 to -25c weather on the highway.


I might heck out the transmission mount seeing in the fall I woul hear a clunk from that area when backing up from time to time.

 

In own a 2003 Corolla. I am the original owner. It has 129,000 miles on it. My idle quality slowly went down over the past few years. It was never horrible but was very noticeable during the cooler winter months. No issue during the summer although it has never been a perfectly smooth idle, it was way worse in the winter. IAC valve was replaced, plugs good, mass air replaced. Never have had a trouble light except when I had a gas cap seal go bad (separate issue). Bottom line was I kept reading that the intake manifold gasket was a big issue on these cars. So that was the last thing I changed about 2 months ago. Took about 1 hour total and cost $7.00. Winter/colder weather idle quality greatly improved. It now runs like it did 6 year ago. I will say that the cold weather idle quality was really only the worst when the engine was just warming up and once it was hot, even in the winter, it wasn't that bad but with the intake gasket change, even that has improved noticeably. No complaints with my engine idle issues now. And the gas mileage hasn't really changed much since all the troubleshooting. With the IAC valve, mass air, plugs and intake manifold gasket replacement parts, the gasket made the biggest difference in driveability.

 

Yea. The gasket was the first thing I replaced.

 

Do you ever run fuel system cleaners? From the tank to the valves? Try a can of seafoam on a tank. If it's a bit better, try it once more. Your stuff may be dirty on the inside. Make sure you pour the seafoam on an empty tank and then fill it up. Worth a try. May be an easy and cheap fix.

 

I might try that. I am wondering if the injectors could be the issue.

 

Make sure to give us an update. Many people take advices, resolve the issue, and don't offer any feedback.

 

Maybe try adjusting your throttle idle stop. You can open it up 1/2 turn to see if it helps.

 

I did and it did bring it up a bit. It smooths it out but it seemed like the IAC did compensate for it slightly which brought the idle back down some but it was still better than before.


Today it was -7c and the car was running beautifully with only a very slight rough idle.

 

If adjusting the throttle stop, it is best to reset the ECU. Simply unplug the negative battery terminal for a few minutes.

 

Won't it relearn still?