wlw-19958 wrote:
> Hi There,
>
> New here. I would like to ask a question about what I found on my
> 1994 Accord when I checked out an idling problem. I found out I had
> Zero compression in No: 4 and 180 to 187 psi in all the others. I
> pulled the head and found one valve that was severely burnt. All the
> other valves look fine The valves in No: 4 have significantly more
> deposites on them than the other three chambers do. Only one of the
> valves (exhaust) in No: 4 burnt (and boy, did it ever burn). The
> other exhaust valve in No: 4 has deposits about equal to the burnt
> valve. The valves in No: 1 - 3 are all clean (well, stained but
> virtually no deposites at all). I checked the valve-to-guide
> clearance on the burt one and it is within specs. The valve stem is
> within specs for a new valve (well above "service" limit).
>
> So, my question is: "why did this valve burn?" Was it:
>
> * Improper valve adjustment,

common.

> * Intake gasket leak,

definitely not.

> * Problem with the fuel injector,

definitely not.

> * Defective valve, or

possibly, but rare.

> * Something else I can’t think of.

if the valve set gets damaged in some way, [think gunk falling into the
cylinder from a plug change, or a plug insulator nose fracturing &
falling into the cylinder - these pieces can get trapped under a valve
head, score the surface and initiate minor leakage.] the leakage will
initiate "burn". it starts slow but accelerates from there.

>
> To give you some background, This is a F22B2 SOHC (non-VTEC) motor
> with about 100,000+ miles (I can’t remember the exact mileage right
> now). The timing belt was replaced roughly 10,000 miles earlier and
> the valves were adjusted.
>
> My first reaction is that the valve adjustment is to blame but I
> checked the adjustments at least twice. Yes, the engine was cool
> (room temperature). It had been up on jacks for a week waiting for
> parts.
>
> I wonder about the deposits on the exhaust valves in No: 4. Why would
> this be the only cylinder to exibit them? Did they develop before or
> after the valve burnt? If before, this would be a reason for the
> valve burning out. But is still begs the question as to Why just this
> one cylinder is developing deposits?
>
> What do you folks think?
>
> -Blue Chips-
> Webb

deposits are because without proper compression, you're getting
insufficient combustion to heat the components enough to clean them.
when you replace the valve & run the car normally, the deposits won't
return.

be aware that this vehicle may fail smog next time around - if too much
unburnt fuel's been reaching the catalyst, it may have burnt out. but
address the valve issue first & see how it turns out.