Okay so i got a 06 civic Si here lately its been doing some weird stuff. On a cold start it makes this pop pop noise from the valve cover then idle drops way down and it starts missing and puts self into limp mode. throwing a code P2647 i put a new vtec oil pressure switch in and it didnt help idk what to do next any suggestions??? im at a dead end! i had it at Honda and they said they dont know and couldnt fix it!
ignore the loud valves its been sitting for like 4 days the pop noise happens toward the end you hear it twice then the idle changes.

 

Maybe a valve(s) sticking occasionally?

 

That sounds mechanical, like gears or levers changing

 

First of all that thing sounds like the valves are chattering pretty bad and it's in need of a valve adjustment. But that popping/clicking noise sounds like it could be a broken valve spring or something along those lines. I would take your valve cover off and have a look for anything out of the ordinary. And if nothing looks out of the ordinary, at least do a valve adjustment while you are in there.

 

Sounds like valves sticking IMO.

 

I found this on another thread for you man


Your engine uses a valve system that essentially has two camshfts, one foor low RPM operation and one for high RPM operation. When the ECU detects that the engine is at higher RPMs, it activates a secondary rocker arm system that changes the engine's valvetrain operation fromm the "slow speed cam" [my term] to the "high speed cam". It does this by (via a solenoid) "flipping" a control valve that redirects some pressurized oil to a hydraulic channel that engages the high speed rocker arms. It's using the oil as a hydraulic fluid.

What's gone wrong is that either
the ECU is not sending the signal based on the engine speed
the solenoid is not switching the valve that redirects the oil
the oil is for some reason not activating the highspeed rockers
or perhaps everything would work fine but the oil pressure is blocked from the valve assembly, which would mean the valve is getting switched by the solenoid but there's insufficient oil pressure to do anything.

Hope it helps!