this is my story / solution, i am posting this in hopes of helpin others.
my 07 fit has 112000 on it all reliable with no issues. at about 109000 my engine developed a rough idle on warm up only and a very loud metal on metal sound when attempting to drive the car before it has warmed up fully. this noise would only last about 10 seconds and would go away wen letting off the gas.
it became slightly worse as milage increaed to current #. i sent lots of time researching and was having difficulty narrowing down the cause. i though it could be a bad cam chain tensioner that would work well once oil pressure built up. or a VTEC issue where it was kicking in to soon causing the rocker arms to slap the cam. there was conflicting information on when and even if the valves should be adjusted? last weekend i decided to check / do the valve adjustment because i felt that was the probable location of this potentialy catostrophic noise.
also becuase i did a lot of research on how the L 15 a VTEC works/ engauges.
i felt it could be the problem but not likely. also if anyone can educate me on L 15 a VTEC that would be great ,as i still done fully understand how it engages the second intake valve.
Anyway i pulled the top end of the engine to get to the valves. this was a remarkably easy process due to the split intake.
what i found was that the exhaust valves were extremely out of spec(tight) and all the intake vales were way out as well ( loose ) getting them back in spec was very easily done thanks to a post from this site on the topic. cant remeber the original poster but he / she had loaded the proccedure along with the factory diagrams ( THANKS ) just a week prior i suspeced it could be the coils so i replaced all four with Beck Arnly coils which do have the vent. I understand this vent is improtant to the longevity of the coil when compared to the cheap E/Bay coils which only last a few months. after coil replacement i still had the same problem. After the vale adjustment ALL IS GOOD. My engine is now butter smoothe with much more power, better gas economy, no more metal noise.
So i conclude that anyone with any performance problems such as stalling, rough idle, nocking / metal on metal noise when the engine is cold , I would go straight to the valves and do a proper adustment. my car runs like it did when new. its amazing how over time you get used to a decline in performance and dont pick up on it. If any dealership or shop tells you you dont need to adjust valves on the fit they more than likely want to keep you coming back for repairs or have you tradein for a new car. i was close to buying a new HRV because i though my engine was on its way out.
have a good day.
hope this was helpful

 

Sorry about some spelling issues and typo's. I forgot to review my post.

 

the economy vtec on the fits uses a valve that is electronically controlled and once your car reaches 2800-3200 rpms, the valve slides up allowing oil to flow into the rocker arm passage and pushes a pin into the next rocker arm thus allowing a switch from 1 intake valve operating to 2 intake valves moving per cylinder.

look at about 2:25 in this video to get an idea of what im talking about. this is actually an r18 engine but the same principles apply.
https://www.youtube.com/watch?v=15qeygZhLzo

 

Thanks for your reply. I kind of figured it was oil pressure activated just could not mechanically see how. So based on your explanation of how the low tec VTEC works it could ? Make sense that when the valves are way out of spec , when VTEC tries to activate the pin is unable to line up properly and will make the metalic noise I was describing. It may also be said that when the motor warms up enough there is enough expansion in the valve train parts to alow just enough proper alignment of the pin for VTEC to function properly
Anyway thanks for helping me try and figure this all out
My car continues to run like new with no issues. I will make sure now that my valves are adjusted every 50, 000 miles
Thanks