Loud Valves, or just Old
 

I've noticed lately that the 'Teg's engine has been sounding like a clattering diesel lately, even when warmed-up and only under load.

For example when cruising and bleeding the throttle, you get that catch-and-coast effect where the play in the transmission either requires a little acceleration from the engine, or it coasts. During the accel portion is when the sound is most noticeable.

I would say that it's a change from the 3-years ago baseline when I took it as the daily driver: much louder.

Honda engine experts: is this perhaps noisy valves? I know they require adjustment from time-to-time. Any benefits/detriments from adjusting them or letting them go???

RH77

I would adjust them...valve tick is annoying but could become a problem. I don't know if this is the real term, but it's what I grew up with. My mom's camry had a bit of it when it got out of time, which was annoying. So get some calipers and measure and adjust...it's not that hard, wish I had the tools though.

Civic DX Maintenance Schedule
 

When I had my '97 DX, I followed the recommended service requirements to a "T" -- which included valve adjustment at 15K miles after they had a chance to seat. I went back to the service bay and watched the adjustment process -- basically a feeler gauge and a wrench, I believe. The technician disconnected the coil wire, and had a switch hooked to the starter to slightly rotate the cam and adjust the next set of valves. I'm curious to take the valve cover off and see what's going on in there. I assume you can check to see if the oil supply tubes are gunked up.

RH77

Your assessment is basically correct. All you really need, after you remove the valve cover is a feeler gauge, the right size wrench and a flat blade screwdriver.

I usually turn the engine over using a socket wrench on the main crankshaft pulley, so I can stop the engine where I wish. What I have done the last couple of times is just look at the engine firing sequence and remove the distributor, so I can monitor which spark plug the rotor on the distributor is pointing at. Then I turn the engine so that the intake and exhaust are both closed on the first cylinder and the rotor is pointing to the first cylinder, which means the valves should be fully closed.

All you do, then is take the feeler gauge, with the right thickness of blade or blades and slide it between the top of the valve and the adjustment screw. If it scrapes, but goes in, leave it alone. If it's too loose, then loosen the locking nut on the adjustment screw, tighten the adjustment screw down to where the feeler gauge just scrapes, tighten the locking nut and recheck the adjustment.

After you do the intake and exhaust on the first piston, then turn the engine over, using the socket wrench, to the second piston and the second position on the rotor and the valves closed, and so forth.

What your describing might also be related to timing advance. When I was fiddling with a fixed resistor in place of the intake temperature, I encountered this phenomenon, more pronounced than previously. Just a thought.

Are they out of adjustment or just sticking?

Have anybody heard of the gas-ATF mixture trick?
I did that every so often on some antique cars I had and made them run so smooth and quiet again.

But those cars didn't have a CAT and not sure what effect burnt ATF would have on it ?

Hot Georgia -

gas-ATF ?????? You made me google and I found this. It mentions gas-kerosene too :

254 stuck valve
https://www.classiccar.com/forums/showthread.php?t=8125
EDIT : Why not disconnect the CAT for the cleaning?

CarloSW2

I'd check your valve lash for sure as any variance from what is recommended will affect when the valve opens...either late or early depending on too much or too little of a gap. It doesn't sound like valves to me though, you'd hear them all the time. I'd check the base timing if it's adjustable on your engine for starters.

-- Scott

i think you are right and perhaps the timing was adjusted earlier for better fuel economy, and it could have been alright with some gas... and bad with other tanks.

fyi, valve adjustment on a b series is A LOT more annoying than a d series. its just the angle. with a d series you can do it with just the feeler gauge, box wrench and screwdriver. with a b series you really should get the tool and bend the feeler gauge to get an accurate reading at such an awkward angle.

Really, the honda engines need valves adjusted? I thought engines nowadays all had shimmed lifters. Learn something new every day.

I wonder if the problem your having isn't something to do with your efforts to control the intake temperature.

When I was fiddeling with the IAT temperature on my 89 it got to where I could hear the engine as it was approaching knocking, but not quite their under load. If you put in some higher octane gas and the clattering sound your describing goes away, then you can be confident that something you have done has the timing a little on the edge of advance.

On my 89 I quit fiddeling, reconnected the IAT and put in new plugs. I think that running it as far out on the edge as I had it, it must have done something to the plugs, because my mileage dropped about 8% but more critically I couldn't climb a grade that I could previously. Before my fiddeling I could pull 70 all the way to the top and after my IAT fiddeling, I could only pull about 60 and it seemed to be getting worse.