Why would my check engine light come on sporadically?

Go to a car parts store in your area and they will tell you the problem for free. They just hook up a machine and it reads your check engine light.

Have you looked at the belts?

Sometimes it can be indicative of a serious problem, but a lot of the time the check engine light comes on when your car has poor fuel efficiency. This sounds like exactly what is happening with your car, as the light turns off when you come out of an idle, thereby increasing your fuel efficiency. I had this same problem a while back with my old Jeep, and I was concerned at first and took it to a mechanic several times. Each time they found nothing wrong, and on the last visit they finally told me that it just had to do with the fuel efficiency. After that, I noticed that when I was driving in the mountains, or idling a lot, the engine light would turn on. But, when I took it out on the highway where it ran better, the light went off. I imagine this is what is happening with your car. If I were you I would get it checked out at least once to make sure, but in all likelihood it’s not a major problem.

AAMCO will also do the free scan.
It could be a lot of things. I will mention the Oxygen sensor.

You need a mechanic you can trust. Which is difficult to find. Unless you have a friend who can help . A friend who knows what they are doing .

It’s an emissions issue, so you might, as an example have a vacuum tube that is flexing, and sometimes has a leak, or you may have a sensor about to fail.

Jesus! 6.55! I take it that’s in Litres?

Yep – emissions. O2 sensors can cause it or the EGR valve.

It’s either of the two things I will list here:

1) You have a loose wire causing an electrical fault (so no real engine prob)

2) You have an intermittent trigger problem that comes and goes, this can be caused by having the car in different states. If the engine is cold then the problem appears? If not does the problem or light come on after you have had the car running for time?