I have a 2002 Toyota Echo with approximately 120.000 miles.
When I first start the car it idles rich of course but even after the engine has warmed up it idles rough when I stop at a traffic light for example. As soon as I apply gas to the pedal the shaking goes away and the car runs normal but for as long as I am still the car vibrates a lot. A few notes that might be helpful. If I put the car in neutral instead the shaking stops completely and the car idles perfectly. The A/C being on also makes the already rough idling worst.
There is another symptom that occurs while idling which may or may not be related to the rough idling problem but I will mention it in case it does help with figuring this out. At times, especially after a long sustained highway drive without stopping, when I come to a stop at a traffic light the car will idles rough as usual but also misfire. Or at least shake vigoursily for a very short time (2 seconds at the most) as if it misfired. I say “as if it misfired” because I took the car to AutoZone after that happened and no codes came up on the machine. It will do it once or twice and then not do it at all for a long time. Sometimes I drive on the highway for long stretches and come to a stop without that happening. This might not be relevant but I figured I’d mention it in case it helped somehow.
I should also mention that I tried to use fuel injector cleaner products in case that was the problem but didn’t help.
Let me know if you have any idea of what the problem might be or if you have any questions.
THANK YOU SO MUCH IN ADVANCE!
All the best,