valve Sound

Hi,

While i was tuning my maf table for the bigger maf house everything was fine so far but i had to change the plug because it got some carbon on it but after I installed a new spark plug which was one degree colder than the old one. And after driving less than 1 hour i had an issue with the engine.

It seems like the piston hit the valve. I was watching my scanner and the short term & Long term seems to be okey

at high load the short term was around + - 7 the short term was less than that but around + 20 short term while acceleration but if i press on the peddle it get down to the normal rang ..

The car wasn't hesitate and it drive okey but when i slow down the engine shut off.

My question:

Does lean afr at low rpm cause the piston to hit the valve ?

or What might happened if any one can give me a clue about it.

NA engine 4 cylinder full bolt on with camshaft ( using short ram intake with Velocity Stack without filter )

What engine is it?

If it the piston hit the valve your engine would probably be dead. Maybe you had some spark knock.

Perhaps your engine ingested something (rock, screw, etc) -- running without a filter can let that happen! Or you just dropped a valve (broken valve spring). Any over-rev events (missed shifts, etc)? Valve float can allow piston to valve contact (which can bend a valve, then the head breaks off...).

Does your cylinder head look like this ?

Thx Arghx7 & David : It's Suzuki Engine M15a

I had same issue before which made me change the whole engine instead of looking for diff head & piston . as the valve drop on the piston coz of miss shifting and the car stop completely .

Thank god that the engine still running but poor power and the sound .. David i still did not open the engine yet. yea i thought the same i said maybe a rock or something went inside . soon im gonna open it and check what exactly happened inside the engine .

So lean afr does not cause this issue ??

I took that picture with a USB borescope (http://www.oasisscientific.com/vividia-va-400-rigid-usb-articulating-borescope-videoscope-inspection-camera.html ) while the engine was still together. It was running, just making a bit of a banging sound...

A lean AFR at low RPM could lead to more detonation (knock), so it's possible you have burned the edge of a valve, or a piston. Only way to know is to look inside the engine. If it doesn't sound right, I would not run it until I knew what the problem was. You might be causing damage that could be avoided.

Thank you David,

yea it looks a grt tool to use .. but it will takes time to arrive here .. so i guess im gonna open it and check.