A couple weeks ago my '05 Accord Hybrid started make a chattering noise from the engine compartment. It does seem that the noise starts or is at least more noticeable when the car is running in 'ECO' mode and running at a constant speed. If I let off the accelerator the noise goes away or if I push down on the accelerator the noise will go away. The noise is also faintly noticeable at a stop with the car in drive or reverse but goes away in park. Also, sometimes the car will surge while traveling around 40 mph.

The car did make this noise shortly after I bought it back in January of this year. I did some research and from what I read it was pointing to the EGR value. So, at first I removed the valve and cleaned it with carb cleaner and re-installed, but no change. Then I ordered a new valve and replaced it. After replacing the valve the noise went away until just a couple weeks ago, so, now I'm not sure if the replacement EGR valve is bad too or if there is an underlying issue. Just for the record when the noise reappeared the weather had turned off cold, don't know that the two are related or just a coincidence.

Thanks