Burnt Valve in 1994 Accord F22B2

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,
* Intake gasket leak,
* Problem with the fuel injector,
* Defective valve, or
* Something else I can’t think of.

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

 

definitely not.

definitely not.

possibly, but rare.

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.

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.

 

Hi There,

Thanks for the information. I suspected that it was the adjustment.
I did the adjustment durring winter and the car was in outside. Could
the colder temperatures affected the adjustment? Should I have added
more clearance to compensate for the colder conditions I was working
under?

Thanks!
-Blue Chips-
Webb