Hello! I have been lurking on here for a while to get repair & maintenance tips, but it looks like I need a little more guidance from our resident experts. This is my wife's car, and while she has no complaints, I can't just let odd engine rattles and blinking warning lights go unattended. That tends to get very costly...
2016 EX-L w/ L4 + CVT
CVT fluid replaced w/ genuine Honda fluid @ 50K miles
Engine mounts, struts & suspension bushings all look fine and do not have play in them
The engine will make rattling noises on cold starts, and particularly when cold or luke-warm and braking down to a stop as the RPM settles back to idle. Now that I have experienced a more severe episode of the rattling, I can recognize that the car has done this to varying degrees for at least the last few years. I come from driving VW diesels and and old BMW with a strung-out 4 cylinder that was not designed with balance shafts and is now fitted with a 7.4lb flywheel...so a "rough idle" in a 4 cylinder does not immediately trigger my spidey-sense.
The Accord's rattle is highly dependent on how long it has been since the last oil change, with very little or none of this behavior for the first few thousand miles. To my embarrassment, likely due to COVID and basically losing track of the last 18 months, I let the oil go almost 13K miles between changes a couple of months ago (I run Mobil1 Extended Performance 5W20, which is supposedly good for 10-12K, but I usually change it at 7K). I had changed the oil on both of our other cars in mid 2021 and must have mixed up in my mind which cars I had serviced. Anyway, what tipped me off was the particularly bad engine rattling and the fact that the oil pressure light would flash on for ~0.5sec when coming to a stop within 2-3 minutes of a cold start. I only saw it do this twice over 3 days. although it may have been doing it for up to a few weeks since my wife is the primary driver of the car.
I checked my records and immediately changed the oil upon realizing my oversight. About 3.25qt of oil was retrieved from the engine, so it was low, but certainly not enough that the oil pickup would have been pulling air under light braking. My assumption has been that the oil was simply old and had undergone viscous breakdown, thinning out enough that the system was not pressurizing adequately. Frankly, that seems sort of unlikely since the oil light never flashed with a warm engine when the oil would have been even thinner, but I cannot think of other good explanations.
So, based on my lurking here and other reading, it sounds like there is at least one problem. The main thing people seem to point to is a faulty VTC actuator. The car's production date is March 2016, which I believe is right around when an updated VTC actuator was released for the K24W engine, so it's anyone's guess which version the engine was built with. However, a number of posts on here, as well as a relatively recent TSB (19-019) indicate that the issue is the timing chain tensioner. Given how many people seem to have the noise return within a year of replacing the VTC actuator, I can believe that the bigger culprit is the tensioner.
Since the tensioner is significantly easier to replace and the car easily falls into the TSB 19-019 range of affected vehicles, I am going to replace that first to see if it helps with the rattle. A question I have is if the faulty tensioner could also be related to the oil pressure light flickering on...when it goes bad, does it basically create a big internal oil leak? The failure sounds like it is related to internal wear in the part, which allows too much oil to flow through and not generate sufficient force on the timing chain.
The parts I plan to order are:
14510-5A2-A02 - Cam chain tensioner (CCT)
14560-5A2-A00 - CCT filter (50/50 on this one, I assume I can just clean the original)
08717-1194 - Hondabond tube
11412-5A2-A00 - CCT access cover
(the following two items are cheap and easy to access, and since it sounds like clogged filter screens are a thing on these engines, I might as well do them while in there)
15845-5A2-A01 - VTC filter assembly
15841-5A2-A00 - VTC strainer body
If the above don't eliminate the rattle noises, then the next items on my list (and a separate project) include:
14310-5A2-A01 - VTC actuator assembly
15830-5A2-A01 - VTC oil control valve assy (relatively easy to get to, seems like it would be prone to any clogging-type issues as much as the other parts)
What are people's thoughts on the first group of parts I plan to replace? Is there anything else I should consider doing while there? The CCT looks like a very easy part to replace, at least compared to the VTC actuator. I am no stranger to working on engines and servicing timing chain systems, so I am up for doing the VTC actuator as well, but I'd rather do other things with a Saturday afternoon if it is not actually defective.