cold start knock / detonation?
 

Can anyone help identify source of noise? attached is a youtube clip.

Happens on cold start only, goes away once idle smooths out after about 1 min of idling. Only started running rough on cold start recently, as temps drop in northern MN, maybe its 40-50 degress @ start up. Motor runs fine once warmed up. I cant find anything mechanical that would cause this, but im still looking. My tuner thought it was something mechanical, my engine builder thinks its something with the tune both of which are hundred plus miles away.. AFR's starting are 12-13 and drop till gauge bottoms out @ 10:1.

stock f22
haltech
gt3076
e85

Wtf that sounds crazy. No clue sorry.

It does have an odd (random) tap/knock, metallic sounding (to me) ...

Of course the tuner says builder and vice versa lmao.

Compression test for equalness
pull valve cover inspect everything (springs, locks, retainers, cams
pull pan rotate engine from crank while you or someone knows what they are looking at inspect bottom and top end.

who tuned it? Shouldnt idle at 10:1

Well I do know one thing for sure, having your afr buried in 10:1 range, especially at low rpm/idle will surely cause fuel washing of the cylinders. Not good! I would get that addressed asap and stop running the engine until you can get some more clues as to what's going on. Smell your oil and see if it smells like fuel, is dark etc and drain it before you plan on running it further beyond your fixes. Don't get the car fixed and then run this fuel washed oil is what I'm saying.

I hope that sound isn't piston slap. Id definitely check for possible outer obstructions, something flapping against the crank pulley, belt, anything rotating on the outside etc. You don't want that sound on the inside of your motor. It is curious that it goes away eventually. That's what made me think piston slap, but that would be really severe if it was, and wouldn't think it would go away being that audible/lose. Pretty much all "built" iron bore/forged pistons engines have some amount of piston slap at cold start up, but it doesn't sound like that, it sounds more like light valve clatter. Could be TCT related, as in chain slap, or chain guild slap/lose. TCT works on oil pressure, could have low oil pressure. Chain/deck height could be off. Few things. I hate built F engines. Too many things that have to go right to get a good one and even then you cant get the mileage out of them like you can an oem because of the inherent piston slap/loser necessary cylinder tolerances. You could have 2 separate issues from both the engine builder and tune. Good luck.

I should add that it ran 100% fine for 2 weeks. The metallic clunking only began when it started with the lopey idle at cold start. Previous cold starts motor idled normal with no lopey idle. I can only imagine the two are connected. I assumed cold start idle is worse now with temps falling in MN.


Fyi this is an oem f22, rebuilt by reputable s2ki member.

Ya that noise could be coming from a few places for sure. I think its some kind of valve chatter or TCT issue. I would be extra curious in those areas.

I would stop running it to. Once you do find the problem, im betting you will be very happy you waited to rip on her anymore than you did.
x2 on the swapping fuel washed oil (fuel is a solvent and will wash the bearings)

First thing that worries me from xp is check spark plugs are tight !!

It runs fine once warmed up. I guess im not proud of how i know that.

If it runs fine @ 8000rpm I think i can rule out anything internal.

That would cause a miss, not really a metallic sound imo.

I understand it has held up so far. At the end of the day i guess it just matters how big your wallet is though. Im still leaning towards something in the TCT (most probable cause) or top end. It could be tune related i guess (warm up ignition table maybe) doesnt sound like an option but you never know with keyboard mechanics and diagnosing. I can tell you i wouldnt be redlining it, but its your car.

I think the sound going away after warm up is a dead give away leaning towards two options spoken above.

Im not driving the car like this. Ill try eliminate all mechanical possibilities.