Anyone familiar with this check engine light behavior?

[mack]

Got something weird going on. The check engine light comes on when I idle for too long (3+ minutes). It usually disappears on its own if I drive it for 20+ miles or so. And it's not a loose gasoline cap (but produces similar symptoms). I went to the exhaust shop to check but they said nothing had cracks. They advised replacing the exhaust manifold gasket but it didn't really solve anything. Anyone have any similar experiences or have any idea as to what's going on? I do have an aftermarket HKS Power exhaust but I don't think that's the issue here.

Also, this check engine light has no effect on drive quality. Car feels fine it's just a major annoyance... I'd almost rather have it stay on then vacillate between off and on.

[soquel1]

Don't think I have ever ran into this.....

Have you pulled the code yet ?

[mack]

The thing is it's not always reproducible. It's so weird. I'm going to try to get the engine light to come on again and head over to the nearest shop. Will update post results in a couple days. Thanks.

[tlikethedrink]

Try to find someone who has a code tool to use it as soon as the cel appears. Or stop at an autozone or something... Try disconnecting your battery for awhile. It will clear the code for sure, if it does come back check it out

[Pronto]

It could possibly be a gasket on your exhaust. So when the exhaust warms up and expands everything is good. But when its cold, there's a small vacuum leak.
Possible codes you might see is P139 and P138. That's what I'm guessing, because I had some exhaust work done a few years ago, and suspect they put the wrong (or reused an old) doughnut gasket (the area between headers and the section before the cat). I suspect its throwing those codes for me because the leak occurs before my cat.
Not saying that its exactly the same case for you, but this might possibly help you narrow your search.

[tlikethedrink]

Op already changed out header gasket. ^^^ maybe donut gasket is right...

[mack]

It could possibly be a gasket on your exhaust. So when the exhaust warms up and expands everything is good. But when its cold, there's a small vacuum leak.
Possible codes you might see is P139 and P138. That's what I'm guessing, because I had some exhaust work done a few years ago, and suspect they put the wrong (or reused an old) doughnut gasket (the area between headers and the section before the cat). I suspect its throwing those codes for me because the leak occurs before my cat.
Not saying that its exactly the same case for you, but this might possibly help you narrow your search.

I'll definitely troubleshoot this by warming up my car and sitting at idle for a while. So far, I've only gotten the engine light from intermittent cold starts. Thanks.

[mack]

Just got the codes:

P1298 (20) Electrical Load Detector(ELD) Circuit Hiqh voltage
P0134 (41) Air Fuel Ratio(AF) Sensor(Sensor1) No Activity Detected