Exlpoding plugs??

[SierraCanine]

What the hell is wrong?? I took the truck to the shop for a misfire.... they told me the number two cylinder has no compression and is "leaking" out the exhaust. It was explained that they would pressurize the cylinder by remov9ing the spark plugs.... they found nothing so I had them put it back together and drove it home to tear apart myself. Well when I pulled the plugs I found this:

The two bad plugs are from the #2 cylinder. They are covered in crud, as is the port on the exhaust manifold on that cylinder. I'm in the process of hopefully removing the head to get a better look but WTH happened to my plugs?!?! The one looks like it quite literally exploded!

 

[ab_slack]

they told me the number two cylinder has no compression and is "leaking" out the exhaust

I am a bit confused. What do you mean the found nothing? Didn't they say the above? That sounds like a finding to me. Maybe they found nothing with the ignition, or bad plugs or fuel related to the miss.

No compression is pretty serious. The fact that it is leaking out the exhaust suggests a issue with the exhaust valve. It not closing all the way for some reason, the valve burned or valve seat messed up. There isn't much more that can be done at that point short of tearing it down, at least pull valve cover and see what is going on. Maybe prior a fiber scope down the plug hole can shed some light but whatever it is, it isn't an easy fix.

Am I missing something?

I off hand don't see why that may cause that plug to have burned up although whatever caused it may have also caused the exhaust valve issue unless the exhaust valve issue is what caused the plug issue.

The replacement plug in that cylinder obviously would look different due to no compression now. It doesn't look like it has burned up but just the dark color that I associate with a cylinder not working right.

 

[RonD]

Assuming '89 2.3l

Lean mixture will overheat a cylinder which can cause spark plug to do that and also cause exhaust valve failure, if it is burned.
Engine is not overheating just the cylinder, you should have also noticed "pinging".

Could be that #2 fuel injector is plugged or broken.
'89 was probably Batch Fire fuel injection, so 2 injectors opened at one time and then the other 2 opened the next time, this kept intake full of fuel air mix, but cylinder closest to a faulty injector would be running a leaner mix

 

[veefer800canuck]

Yup, no compression, the head has got to come off.

You're looking at a rebuilt head, and probably new injectors. O2 sensor replacement wouldn't hurt as long as you're in there.

Hopefully you don't find a Sunday piston when you take the head off....... that will be worse.

 

[Andy D]

Different truck, different time , same trouble caused by a terminal overheat. Pinged a hole in a piston in less than 25 miles on Datsun 4 banger. I fixed it. But it was a PITA. You likely burnt a valve in the hottest / leanest cylinder. This is why solid tappets need adjustments. Are there shops that rebuild heads locally? Do shops still do that stuff?

 

[SierraCanine]

Well got time to take her apart and found the problem. It looks as if the bit of spark plug that broke off managed to impact the exhaust valve and put a nice hole in the side about a centimeter wide -__-

 

[RonD]

The cause of the damage probably didn't start with the spark plug.

If the spark plug "broke off" and damaged the exhaust valve then that cylinder would stop working at that point and both spark plugs would look clean.

Because of the condition of the spark plugs a Lean mix most likely heated up the cylinder causing the plug to melt and crack, could have been the plug on the exhaust side as that would be the warmer plug.

 

[veefer800canuck]

the spark plug probably melted off, not broke.

you probably have a preignition/detonation problem, which began the whole chain of events.

Better fix that while it's apart, or it'll do the same trick again later.

And agree with the others, a lean mixture is a good place to start looking. Injectors and O2 sensors, fuel filter/fuel regulator/fuel pump all should be examined.