Shakey Graves

Hola, I need to pick some forum brains here. 

I have a 2004 Acura TL. V6, 6-speed, FWD (obviously), 195k miles. When the winter hit I started getting some vibrations on startup, and while sitting (stoplights, etc) coming from/in the engine bay. I have no CELs, all my gauges are reading great, and I feel no shuddering or vibration while in gear and driving.

The vibration seems to have no positive correlation to engine speed or car speed, other than it occurs when I am stopped and out of gear (or at least other noises and movement drown it out when I am driving). As far as maintenance -I bought the car 30k ago, and it is time for my timing belt change (and tensioner, water pump, etc), and spark plugs. 

With this info, I have tossed suspension out of the question. I will crawl under it this weekend and bang around to try to find something loose, but other than that I am sort of stumped. Doesn't seem like plugs would do it as I would always feel it. Same for fuel filter, timing belt, etc.

What say the hive mind? and thanks in advance!

Oh and I did put a stronger Engine torque damper in recently (the old one was completely shot and I could depress it with one finger). 

So my mind went to broken engine mounts... but there's no excess shake when putting it into gear or taking it out, so I assumed that was not the issue.

Which as I ponder it, I need to check the torque damper hasn't rattled itself loose since it's my only new part there. That or I am just going to feel some vibration since the cold contracts everything and its a relatively hard damper. 

It just doesn't "feel" like a natural vibration.

I'd start with that tune up you need to do anyway. I'd say you could easily have an idle unevenness that might now (edit: might *not*) throw a code but could make for a rough idle without showing up under load (when conditions for combustion are generally better).

If sparks plugs don't help, at least you haven't put in any work that didn't already need to be done and you can continue troubleshooting.

In reply to Jesse Ransom (FFS) :

True, and good point. I will try to get to that this weekend! Thanks!

I'd check all of the engine mounts. If it's similar to an Odyssey, there will be three mounts: front, rear, and side (near the accessories). Unfortunately, visual inspection is very difficult, my front mount looked fine, but was toast.

I'm betting engine mount. Sometimes you can see excess engine movement when one is borked, but sometimes it's just vibration. Modem mounts have a LOT of design time spent on NVH mitigation. 

In reply to ultraclyde (Forum Supporter) :

Thanks- I have an inspection camera so in theory I can at least get a pretty good look!

Yeah, and you might not be getting noticeable shaking and such in gear/accelerating because the engine is "loaded" and twisting against the mounts.  It's in neutral that any natural vibration will be able to sit there and wiggle.

I've been able to test this before with a crowbar, have the car idling and try to apply leverage near the mounts (in the direction of the mounts) and see if it gets better.  I don't know if your car has access to do this easily, though.

With the hood open, put the car in drive. Look thru the bottom of the windshield at the motor, brake torque the motor. Hold the brake and give it throttle. See if the motor lifts 2-4 inches. If it does the front mount is bad. Now do the same thing in reverse. If the motor lifts the rear mount is bad. 
For the transmission mount I don't know. 

Welp, Not saying for sure yet, but it seems to have been the plugs. They were quite used.

The shake wasn't immediately cured, but after a 20 minute drive (highway back home), when I stopped it felt much smoother. So hopefully I'm not imagining it as I am hyper sensitive to it, or the other explanation would be heat related.

It is not engine mounts, those feel look and feel good. Hopefully it is cured tomorrow morning when I cold start it.

Thanks everyone for the help!

Ugghhhh. Ok, so not plugs, and not timing belt. The shake is back, yet seems lessened- can't tell if it's me or not (as in a placebo affect). 

I should clear this up- there's a "knocking vibration"  that's the best I can describe it  

At 1200-1300rpm, when the engine starts, there is no knock. At 800rpm (about 30 seconds after turning on from completely cold), I get a knock. Goes away if I rev it. 
 

I tried brake torquing the motor in 1st, and reverse. Same in neutral. No noticeable movement. 
 

Next work for me is to replace the PCV valve, and replace on of the coils that showed some corrosion.  
 

Still no CELs. That's what makes me think it is not a sensor. 
 

Any advice?

Well, I keep searching Acurazine, and I found this thread: 

Link

One of the most telling comments was :

"For all the proposed solutions I've heard for the knock:
Valve adjustment - that's never fixed it - they're never that far off
Timing belt tensioner - sometimes that's it, but it makes a distinct sound
Hydraulic lifters - the TL doesn't have hydraulic lifters, so that's definitely not it
Timing belt - plenty of people changed this and still had the noise
Piston slap - possibly, but I'd expect more than one cylinder slapping - all these engines that knock seem to knock at the same frequency - about 6 times a second at idle
Spark plugs loose - sometimes that's been the issue
Rocker arm bolts loose - I'm not aware of anyone checking these on the TL but there is a TSB out for newer Honda V6 engines
Exhaust manifold/bolts - I'm not aware of anyone checking these
Accessories - plenty of people have taken off the accessory belt and still had the knock"

It all sounds pretty similar to what I am experiencing, although there are several iterations and proposed solutions. 
 

The most common answer is "drive it until it dies", which many people are saying could be years later. 
 

Antother guy says "After I get past 2K RPM either cruising or full throttle, the engine sounds beautiful and has the same power as the day it was new", which is what I experience. 
I guess now that I have a new TB service, and new spark plugs, I'm good until this engine breaks (or, at least the break even point for putting money into this specific engine has been reached). If it fails, I guess I'll learn how to swap an engine! 
 

The clutch is also at 200k miles, so at least that would be a good time to do the swap lol. 

At 800 rpm, 6 times a second is about one cylinder, half crank speed (i.e. not piston unless it matters whether it's under pressure; but about the rate of one valve).

I'm not sure there's anything amiss, but if it's really bugging you, it's no good listing the problems other people have had or not had, especially when their results are not uniform/unanimous; within reason you need to verify each for yourself. Based on the speed thing, I'd be trying valve adjustment, regardless of the "that's never fixed it - they're never that far off."

Replacing (or at least cleaning) the corroded coil sounds like a good one, going back to the notion that it probably would be worth cleaning even if you weren't trying to diagnose anything, though I'd expect this to throw a CEL if it were really having issues. Doesn't sound like the right noise for an injector, but the timing is right (er, if these are a once-per-cycle sequential, which I have no idea about).

In reply to Jesse Ransom (FFS) :

I agree listing other problems isn't going to get me to an answer, and if I had more experience with engines, I may try to diagnose further.

Like you noted, I'm not about to just throw parts at it, but I might as well get the things that need maintenance regardless of my "problem", or, lack of problem lol.

I was listing those more for brainstorming than anything. I think that if I don't have a CEL, there's not much to diagnose for me (or, more likely, diagnosing anything will get me over my head, or over my allowable budget for a daily)!

After the coil and PCV, a valve adjustment is probably a final stop for me.... after I get all my suspension crap finished lol.

Again, thanks for the help everyone!

In reply to russ_mill :

Hey, this is how you get that experience!

Anyhow, sounds like you've got a well-chosen to-do list. Have fun!