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 canít think of.
To give you some background, This is a F22B2 SOHC (non-VTEC) motor with about 100,000+ miles (I canít 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
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wlw-19958 wrote:

common.
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.
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"jim beam1" wrote: > 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 canít 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 canít 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.
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
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