Maybe it was caused by bad Vtec.

Maybe it was caused by bad Vtec.

 

Are you serious?

 

Twitch

Maybe it was caused by bad Vtec.

 

 

 

But seriously. No, Vtec didn't do it.

 

I did notice the wear pattern on the seat of the old valve seemed to have a curved profile. When I "ground" it, the small high spot on the seat flattened out. Wondering if the wear might be abnormal, and if so could it have been a contributor to this case?

 

This engine did also have a faulty knock sensor...

The bad knock sensor very well could explain a lean condition, as the computer may have been in limp mode.

An uneven seat very well could have been the culprit, but it may just be a side effect of the valve burning out.

If it was under the hole in the valve, then the uneveness could just be material deposits from the burn out.

 

And just an FYI SubaruPlatt, Subaru's don't have V-tec.

We get power through the whole rpm range, not just from 6k up.

 

Twitch

this thread is turning hilarious.

 

first we have vtec.

 

 

then we get an uneven seat reason as twitch noted.

 

lol, uneven seat, get it, when the seat side cushion is worn lol it makes you sit uneven....

 

no just kdding i get it, valve seat......right?.:-\

The bad knock sensor very well could explain a lean condition, as the computer may have been in limp mode.

An uneven seat very well could have been the culprit, but it may just be a side effect of the valve burning out.

If it was under the hole in the valve, then the uneveness could just be material deposits from the burn out.

 

And just an FYI SubaruPlatt, Subaru's don't have V-tec.

We get power through the whole rpm range, not just from 6k up.

 

Twitch

I did say maybe. I did some research and...

Subarus started getting a v-tec system called i-Active Valve Lift System in 2005.

http://en.wikipedia.org/wiki/Active_Valve_Control_System

Not new enough to have it ( my mistake ).

 

and by the way I also suffered a valve failure and dropped valve guide as a result.

http://www.ultimatesubaru.org/forum/showthread.php?t=114013

Edited March 3, 201115 yr by subaruplatt

Well, not to be a party pooper SubaruPlatt, but this discussion is about 2.2L engines.

Those stopped being produced in the US in 99, I believe at least for legacies.

And I was aware of Subaru's addition of the variable valve timing system they added in 2005.

But it didn't apply to the discussion at hand, so I dismissed it from the start.

 

And please don't apologize for me not being able to afford a new enough Subaru to have i-Active Valve Lift System, I enjoy having an EA81.

Simplicity is king of reliability.

And if you'll note, most of the members on here have never owned anything newer than a 3rd Gen legacy, if that.

 

Now please don't take this reply as an attack, I'm just trying to bring you up to date on what items are applicable to this discussion

 

Twitch

 

PS: V-Tec, is a Honda trademarked term, and refers to a different design than what subaru offers

lol, uneven seat, get it, when the seat side cushion is worn lol it makes you sit uneven....

Just lean the other way. Or drive from the middle like a thug.

 

 

The bad knock sensor very well could explain a lean condition, as the computer may have been in limp mode.

I guess I'll never know, but the combination of things just spells disaster IMO.

 

Subaru AVLS is nothing remotely similar to Honda Vtec. AVLS advances camshaft timing, but does not change valve lift or open duration like Vtec does. The lift and duration change of Vtec is why you can hear the pitch of the engine change when Vtec "kicks in".

Hi

 

Haven't read a whole topic yet, but I just want to say that I have also similar problem. The same exhaust valve, gone twice.

Subaru Impreza GF6, 1994, 1.8 [ EJ18, SOHC, naturally aspirated ] AWD, European spec.

 

I bought car with ~205'000km, and after some 4 months driving exhaust valve was gone.

 

I changed whole head (from bit newer engine, it was said to be 1.8 USDM), and it run ok for some 14 months, around 15'000km. And then again - the same cylinder (#4), the same valve was gone.

What's the reason for those deposits on valve face?

 

both heads:

newest below, oldest above.

 

Removed pistons as well, because I thought that cause is oil that gets in cylinder. All seems fine:

 

As next I'm going to check ignition cables, spark clubs must be ok, since they were changed short after first engine head was gone.

For a pity I don't have equipment to check injectors, probably that's the fault.

Edited November 1, 201114 yr by DimanC

That's the only issue with the theory - which occured first, the burned valve or the zero clearance.....

GD

 

Interesting thread. Chicken or the egg? Well I would say that zero clearance caused the burned valve. In my experience adjusting valves on cars and motorcycles, mainly with screw type adjusters, intake valve clearances increase while exhaust valve clearances decrease over time.

 

Accordingly, I always adjust my exhaust valves to the upper limit of of the specified range and intake valves to the lower limit.

What's the reason for those deposits on valve face?

 

 

That is melted valves. You have some serious heat going on in that cylinder. I'd definitely swap injectors. One valve could be a clearance issue, but both valves looking like that... Not good. Could be a valve seat issue, fuel, a bad intake gasket letting in too much air, any number of things.

You should definitely check and adjust lash clearance, and make sure the fuel injectors get replaced, at least with a junkyard set before you put that back on the road.

That is melted valves. You have some serious heat going on in that cylinder. I'd definitely swap injectors. One valve could be a clearance issue, but both valves looking like that... Not good. Could be a valve seat issue, fuel, a bad intake gasket letting in too much air, any number of things.

You should definitely check and adjust lash clearance, and make sure the fuel injectors get replaced, at least with a junkyard set before you put that back on the road.

hi

Thank you for yout opinion. I shall check all things - injectors, air leaks in intake gasket (current manifold has two gaskets...), ignition.

But I'm 95% sure, that valve itself IS NOT melted. Melted are those deposits (or how do you call them), on valve face. If you take a look at my previous head - it looked exactly the same, and after cleaning that black sh1t from valves, they don't seem to be melted, you can clearly (despite to blurry picture) see all symbols on it:

but whatever - I agree, that possible reason of broken valve is too big hot in cylinder.

So that stuff came off? Hmm, that's really strange. I've never seen heavy deposits like that. Burnt valves are usually pretty clean because they get so hot anything on them just burns off.

 

I wonder if the burnt valve is a result of the buildup then? Possibly the seats are too wide so the valve cools too quickly and the deposits build up. But then some of the crud broke away and allowed enough heat in one place to make a hot spot and melt the valve?

 

Maybe someone who knows more about it will chime in. :-p