uberlawyer

Hi all, my first post here, so greetings to everyone. I've had a strange thing happen to my 1996 RoW 4S: I was starting from the lights, I accelerated (not very aggressively) and all of a sudden the engine started making a loud noise, as if it was running without the exhausts. There was also a faint gasoline smell.

After my knowledgeable friend has arrived, we have determined that the upper spark plug for piston #3 (left side, farthest away) has been thrown out.

My friend (who manages a service shop) says he has never seen something like this. We do not know at this point whether the crankcase has been affected, but we have managed to put the spark plug back in and rotate it by hand a couple of threads, so hopefully everything is ok. The first 2-3 threads on the spark plug had some wear.

The engine ran perfectly after putting it back. I'll know more tomorrow when I take it to the shop.

Any thoughts? I hope that maybe it was not properly tightened and vibration and the compression took it out.

Would this explain the non-linear accelaration and deceleration that I was experiencing? The engine braking (suddenly taking your foot out of the loud pedal) was especially brutal, and acceleration was not smooth, either.

Sorry for the long post and thanks for the assistance

pp000830

Had this happen on an old Ford. The plug was not properly installed and worked its way out. No biggie. If you put the plug in properly and it seats well you are done and all the symptoms you describe will be gone

Bill Verburg

It's a surprisingly common occurrence

a couple of the plugs on a 993 are very difficult to properly torque while the engine is in the chassis, they will work themselves out. Often the head threads are damaged and will need to be repaired and sometimes other damage occurs too, things like the power steering belt and valve covers.

Aaron 993C2

This happened to my motorcycle last week, correct torquing is the key to making sure it doesn't happen again. When installing the plugs watch out for anti-seize or thread-lock compounds that some people will use, these can throw off torque values and cause more harm than good.

pp000830

Anti-seize is made with copper or other metals that can serve to foul the plug. Seeing that the head is made of soft alloy I am not sure of the need for anti-seize in the first place.
Andy

Aaron 993C2

Agreed, don't use them.

knorrena

I dont agree. If used properly and sparingly, the plug does not get fouled and prevents galling, and increases conductivity between the plug bod and the engine. I have busted plugs in the head twice. Its a bitch getting them out. I far prefer using a wee bit of antisieze over removing a busted plug.

nine9six

I gotta say, I'm with Karl on this. Sparingly is the key.

IXLR8

If the threads in the cylinder head are fine, then it should take roughly 14 / 1.25 = 11.2 turns to fully seat the spark plug...by hand so that you can feel what is going on.

And use anti-seize...commonly done when you have alloy heads. All you need is a thin coat using an artist's brush; I never use the one that is attached to the cap of the jar. I was able to torque all the plugs in my car using the minimum torque specification.

nsully

Autolite T-556 Spark Plug Thread Lubricant & Anti-Seize Compound

Cupcar

I think it important to hand tighten and feel a substantial number of turns to seating before using a torque wrench.

Anti-sieze helps feel a true seating of the plug in my opinion.

Fully tightening to torque a cross threaded plug is a nightmare.

uberlawyer

Many thanks to all for your suggestions and comments. It appears that all is well and the thread is ok. They managed to get a dynamometric tool in there and torque the plug to spec. The rest have also been checked and seem ok. I understand no anti-seize has been used.

I attach some picture of the car with the rear bumper removed. I cannot help but notice the excellent advice both here on on jackals-forge.com regarding rust under the rear lateral support.

Luckily for me, the rust situation was not that bad - the car has been full repainted and some compound has been used on the supports, but still there was some rust that now will be addressed.

I have however ordered several heat protections from carnewal - some of them had seen better days. Let me tell you, they ain't cheap...

Later edit: the catalyst heat shield is new and has a production date of July 2014