Regardless, this information you provided is useless for the topic of discussion.
It certainly doesn't help OP (or anyone else) properly address the rattle.

 

Just combating misinformation as it pops up.

 

Good for you.
Hopefully that works out for you elsewhere.

 

Just ignore the "Know It Alls".

The "Know It Alls" have too big of an Ego they need to validate on mere mortals.

 

That is sad and depressing news....for one mustering up the courage to replace spring

 

Okay, I've got all the parts for the spring replacement (not installed yet), but I haven't heard it rattle in a week or two. I'm not sure what to attribute that to. Change in weather? Additional cleaning action from changing the oil with 60% life on the maintenance minder? Could VTC rattle be prevented by replacing the oil 2 or 3x as often?

Since I still haven't had an actuator to pick apart, I previously wasn't sure what the spring-loaded piston in the VTC actuator did. I thought it might be a relief valve? The paperwork that comes with the Spring Start kit calls it a "locking pin". That makes me think it spans the gap between the hub and sprocket portions of the actuator, locking them in a neutral position. When there's no oil pressure, the spring pushes the pin into the locked position. When oil pressure is applied, it pushes on the opposite face of the pin, driving it against the spring like a hydraulic piston. Oil pressure drives the pin out of the sprocket half of the pin-bore, unlocking the actuator.

What turns the actuator back to that neutral position when the engine is off? Is there a clock spring I'm not seeing? It would have to be pretty strong to overcome valve spring forces. Oil pressure drops after the engine stops, so cam drag seems unlikely. Is the locking pin expected to drop into position during start-up?

 

all EXCELLENT questions...my OPINION sort of aligned with yours where if there is NO oil pressure it "lock" the cam,until the pressure build to "variate" the position, i wonder what would happen if you just put a straight pin and LOCKED it premeneantly

the non neutral position on off may be the ENTIRE problem!! i think you are right about it "supposed to drop into neutral position on startup"

 

reading the entire post just FYI i was under the impression the valve timing was "real time hydraulically varied" it was not a "pin or nothing" scenario like 0 or 1....soooooooo is it 0 or 1or variable?...thoughts?

 

That's also my understanding. When oil pressure is available, it's dynamically controlled. The pin seems to exclusively deal with the no-oil-pressure condition during startup.

While watching a few videos of K-series VTC actuator teardowns, I realized there's two sets of oil passages fed by the cam shaft. One is a set of drill holes from the counterclockwise end of each chamber to the cam shaft. The second set is cast into the back (cylinder head facing) surface of the hub (such that the actuator's rear plate acts as one side of each passage), connecting the clockwise end of each chamber to the camshaft. When I say chamber, I mean the space between arms of the hub. An arm from the chain sprocket portion of the actuator sticks down into that chamber, dividing it in two. When the actuator is full of oil, pumping oil into one end of the chamber (actually all the chambers act together) should drive the sprocket-arm-divider towards the other end and push oil out through the passage on that end. It's a cluster of double-acting hydraulic cylinders, but in rotary form.
Oil passages through the camshaft, cam bearing journal, cylinder head, and timing cover connect those clockwise and counterclockwise actuator passages to the VTC solenoid valve. The solenoid is a spool valve (also common in hydraulic systems) which applies oil pressure to one passage and drain (back to the oil pan) to the other. When power is applied by the ECM, it swaps those connections. That lets the ECM adjust the cam phasing (timing) in either direction, or hold it steady by rapidly cycling the valve on and off. A dedicated camshaft sensor lets the ECM calculate the current cam phase angle, which it compares to a target value to decide what to do with the valve.

When the actuator is pushed all the way to one end of its travel, the locking pin bore on the hub lines up with an empty bore on the back plate (the plate is attached to the chain sprocket / housing). The back plate bore is full of oil, but connected to the "drain" passage. This lets the locking pin spring push the pin from the hub bore across to the housing bore, locking them together. When the VTC solenoid swaps the pressure and drain connections, pressure gets applied to the housing bore, which ejects the locking pin, unlocking the actuator.

So air in the actuator is "the problem", but is an expected occurrence. The locking pin is supposed to hard lock the hub to the housing so it can't flop around during cold startup. If the lock doesn't engage and there's air in the actuator, you get VTC rattle. I could see a weak or short spring causing problems. Maybe concentric misalignment of the hub and housing? I guess a machining defect like inadequate deburring is too obvious - someone would have found that early.

 

Exactly what was happening on my Fit. You still need to replace the spring. Also, you need to replace the timing chain tensioner, that is what Spring Start recommends as the best solution. Because the spring lasted a while until I started getting a different type of rattle sound. It has all gone away completely when I replaced the chain tensioner recently.

 

Does tensioner replacement require removing the whole timing cover, or just the access plate?

 

You just need to remove the access plate. Used scotch brite gray pad to clean surfaces and a fresh tube of Hondabond.

Pic from when I replaced it last month

 

Sounds easier than doing the starter.

A little silicon carbide dust on the timing chain won't hurt nuthin.

 

There wouldn't any silicon carbide dust going into the opening if you just carefully wipe away from the opening. It's an awkward position to do this, just make sure you have double or triple safety under the car since your body will be right under the front rotor.