PleaseW84myRX8

Having persistent issues with a 2000 Honda Civic LX.

Got a used civic that got about 33.3 mpg when I first got it.

Did some casual maintenance and tune up work like air filter, plugs, etc and got 33.5 mpg. Big woop.

Had a loud knocking, so I did a valve adjustment. .007 intake, .009 exhaust. To clarify, the exhaust side is facing the front of the car. I rotated the crank each time and made sure it was in the correct position.

After my first adjustment, the car sounded great. Smooth, silent, and it felt like it was accelerating better. Got only 34.2 mpg after this adjustment during that whole tank of fuel. Issues occurred about 3 starts after the first valve adjustment (less than 50 miles driven by this time). The knocking came back and the vibrations came back. Drove through another tank of gas and got only 33 mpg.

Did another valve adjustment. Maybe I didn't tighten something properly. Same thing, worked great for 2-3 starts, by the third start (~45 miles), knocking came back and car only got 34 mpg with the first tank, 30 mpg on the second tank. We got hit with a snow storm and the roads weren't cleared for 2 days which I think is what happened on the other 3 mpg.

Valve adjustment 3 to get rid of the knock again. Same exact problem, only now, no snow and clear roads, and I'm getting only 27 mpg. I checked and double checked after valve adjustment 3 and everything was tight and in perfect position during adjustment.

WTF is going on? Why does it run great for the first 2-3 starts, and then by the 3rd start the knock returns, engine vibrations return, and the car gets horrible fuel economy? I do not race this car, it is a daily commuter only. So it isn't like I'm abusing it.

mk378

Valves don't make a knocking sound, it is more of a tapping or clattering. Likely something else is wrong. Also the engine doesn't misfire or "vibrate" unless the valves are too tight.

When the complaint is low mpg, the first thing to check is timing.

chrysler kid

The expansion properties of aluminum will change depending on the temperature of the cylinder head. The amount of carbon deposits on the cylinder head also cause a variation over time

These cars were never dead silent. A typical d-series should have light chatter at idle that disappears into engine noise as your accelerate. If you can hear ticking over the sound of your engine revving there is an issue

However so far I havent heard you describe any unusual problems. Depending on your driving habits and wheel size 33 miles per gallon is normal for the lx, and snow or severe conditions also can cause the 27mpg reading.

PleaseW84myRX8

Just want to clarify, pretty sure it is a knock, not a tick. I'll try and get a video of it today, but I have to wait for the car to cool down because that is when it is most noticeable. I'll update with a video later. The knocking gets faster and slower as the revs go up and down. This knocking does not exist for the first 2-3 times I drive the car after each valve adjustment. After about 50 miles it comes back just as loud as before an adjustment.

The car runs great during these first 2 times. But once the knocking comes back, it feels less peppy (not that these cars are to begin with, so it is very noticeable when there is a slight performance drop), and the vibration in the engine is just noticeably worse.

The 27mpg was not achieved in snow. The 30 mpg was achieved in snow. After valve adjustment 3, it got 27 mpg with NO snow.

I put timing on the to-do list, but why would the car work properly for the first 50 miles, but then not work if it was a timing issue? Shouldn't it be just as boggy right from the start?

A new development on valve adjustment 3, I drove around all day yesterday and two out ~60 stop lights, my idles dropped below 300 rpm and felt like the car was about to die. I had a car that had this issue and it was a faulty solenoid keeping the auto transmission from shifting to first. So maybe that is a new development. Not sure if it is related. This is also on the to-do list to check. The idle drop did not occur the first two adjustments.

tony_2018

What temp is the engine when you perform these valve adjustments?

PleaseW84myRX8

Cold. Each time the car was at rest for at least 24 hours. Ambient temps have been around 34-40 degrees outside each time.

tony_2018

What order are you adjusting each pair of valves?

PleaseW84myRX8

1,3,4,2

"Up" points up on the crank for 1, then I move it left, then down, then right.

tony_2018

were the cam lobes making contact when the 'up' was at 12, 9, 6, 3?

PleaseW84myRX8

I don't believe I specifically looked at the cam lobes. Thinking back, I think it was underneath everything and I didn't see it.