Wondering whether the Fit's valve clearances tend to drift toward tighter or loose over time? I'm probably overdue to have them checked. My '09 Fit auto had the LM spring recall done at about 15,000 miles, so they would have been set then. I'm now at 61,000 miles. Fuel mileage is not what it used to be. It's a struggle to get 29 mpg city w/AC full time. Computer is always 2 mpg optimistic, so I do the math to get real numbers.

Just took a 900 mile road trip, started off getting just over 32 hwy, up to 36.5 by the time I finished the trip, 75-80 cruise w/AC. Still pretty crummy IMO. I'm debating as well if it's time for a fresh set of plugs along with a valve adjustment. I stick with top tier gas (Shell, Chevron), tailpipe finger check is clean.

 

Your mpg figures sound good. They're not meaningful though without knowing history and if your driving habits have changed.

36.5 hwy with A/C averaging 75-80 is better than good.

As for valves, the exhaust tend to recess and become tighter while the intake looser.

The MM flags plugs and valves sometime after 100k. 30K valve adjustments are not recommended by Honda.

Honda's rate to replace plugs and adjust valves is over $400.

If you have it done, let us know if it improves MPG.

 

Wouldn't mind doing the plugs myself, is there a GOOD take-apart video/slideshow somewhere showing step-by-step cowl removal and taking off wiper mechanism to gain access to the packs/plugs? Formerly owned a Civic, which was a 10 min job tops, full access.

Even though 100K life is "claimed" for the plugs, my mileage patterns reveal poorer overall mileage/performance relative to when they were "younger", and the fact that they always seem to "clean up" and mileage improves after an extended highway trip. A long trip involves no cold starts or short trips, lean A/F ratio, stable engine temps, and medium/light load operation for more than several hours under stable conditions. Minor variation in fuel quality due to different stations along the way maybe (I burn 87 regular).

You see what I'm getting at? My driving style and routes are pretty much the same as when she was new. Yeah, it's kind of a rape by Honda for all that labor. Wouldn't you think they'd of designed a removable access portion of the cowl or panel area to accomplish tasks like this w/o 5 hrs labor ??? Just my 2 cents....

 

The cowl is designed to be removed so that's taken care of. Access to the valves requires removal of the intake manifold chamber which includes undoing all the electrical, cooling, and vacuum lines to the throttle body. In addition to the valve cover gasket, you'll need new manifold gaskets. Plugs and gaskets will run close to $100. I'm guessing 2.5 hours for a pro. Two days for me.

I don't think used plugs are a problem unless they're fouled to the point of causing misfires. These would be detected and codes thrown. In spite of manufacturer's claims about spark plug performance, I've never seen a difference between worn and new plugs, as long as they were changed at recommended intervals. Anecdotal accounts have the OE plugs lasting well beyond 100k.

I'd look for another explanation for the increase in MPG the farther you got from home. Possibly the fuel blend was different away from your home (as you noted). Seasonal differences in fuel blends plus using the A/C could explain the lower MPG.

Of course it could be plugs and valves, which is why I'm eager for you to try it and tell us if it makes a noticeable difference.

edit: I'll transfer the relevant pages from the shop manual to pdf and post tonight.

 

if you're going to go through the trouble of adjusting the valves, I'd recommend checking that the plugs are snug while you're there.....mine loosened (especially 3rd cyl) over time.

Also buy a good amount of plastic clips for the cowl, they break easily and even the dealership wont replace all of them when working on the car....

Personally I've adjusted my valves once and have had honda do it twice afterwards.....

 

go to autozone and buy a set od Denso plugs for a honda s2000

gap them to .051, and install them

Cost $32 or so, and is an upgrade.



Do the valve adjustment. Id recommend doing it at a minimum every 30-40k miles after that first one was done. Or at least having them checked

 

Here are the shop manual pages on plugs and valve adjustment (no particular order, it jumps around (manual not car)). Sorry about the blank pages, it's about 17 pages of actual text.

I recommend doing them when the MM flags it, or if the valves are excessively noisy (per manual). YMMV

 

Thanks, Steve. Saved for when I'll tackle the job. Hopefully in another 2 yrs, not sooner.
Did you apply any silicone gasket material to the corners of the intake manifold? I remember reading that it was necessary and then letting it dry for several hours before starting the engine.

Did you notice any change in engine sound after adjusting the valves?

 

I have yet to undergo the joys of valve adjustment. Except for Honda doing it at 25,000 miles for the Lost Motion Spring Recall (sounds like a good name for a thriller). At that time the valves were less noisy for a few days, but then resumed their normal clickety-clack when cold. This always goes away after the engine has warmed up (3 miles or so of driving), even today at 75K.

I won't be opening it up (or paying someone else to, I haven't decided) until after the MM flags it, or they start making excessive noise while at operating temperature. I expect this to be sometime after it hits 100K (7 years old at my current rate).