[Bigbadspoon]

This is my first post here, but I've been lurking around for a while. I've been having a hard time finding info on this kind of problem on google or alldata, so I figured someone around here may have had a similar issue.

I've been hypermiling on my Civic (D16) for a few months now and average 39ish mpg (silly Gov. Crist put ethanol in all our gas. Before that went through I was at 42). Anyway, under very light throttle and cruising around 40 mph (2000~ rpm) the engine seems to surge on and off. Letting off the throttle to engine brake doesn't seem to fix this. Whenever I drive heavy on the gas, it goes away.
I've discussed this with my old automotive teacher and he proposed anything from failing EGR valve to bad O2 sensor and everything in between. We had a hell of a time trying to diagnose it. All the sensors checked out, but we didnt have much time to check the EGR.
I thought perhaps it was spark plug heat range? But of all the manufacturers I've checked no one makes a plug hotter than stock for that model of Civic. Also, I've thought it may be a fuel delivery problem, but since it happens during engine braking makes me think that is not the issue (since fuel pretty much stops being delivered).

Besides this issuue, I have noticed a very slight miss when revving up the engine in neutral. Under 2k rpm, the needle just seems to bounce up an down a little like a misfire, but hooking up a scantool shows no signs of one.

Anyhoo, if anyone has had a similar issue with their car, let me know. This thing is driving me nuts!!


-Spoony

Also, just did a full tune-up a month ago. (Platinum Plugs, wires, cap, rotor, fuel filter, air filter, pcv). The problem existed before the tune-up as well.