Ok, I searched around and could only find one reference that even closely related to my problem..... I drove my runner around yesterday during the day, went home and parked it (everything was running just fine) So when my wife and I went to leave a few hours later, I started her up (the runnner, not the wife ) and as we drove away I heard a very hollow sounding popping noise. The first thing that came to mind was an exhaust leak under the hood. The only thing that effected the problem is if I revved the engine. So... I pop the hood to discover that the spark plug (very front driver's side, don't know the cylinder number) had worked it's way out. I went ahead and pulled it all the way out and the threads, gap, plug itself were in great shape. So I just decided to go ahead and tighten her back down. The problem seems to be fixed now. Noise went away.... my question is, has anyone heard of this happening before? is there anything I need to look out for in the future? What caused this?

more info if needed... 1999 SR5 4Runner, 160 k, don't know what else would effect it so let me know if you need more info!

Thanks so much in advance for the help!

 

That's the #1 plug. The only way I could see that happening is if the spark plug was not tightened properly in the first place...
I've seen plugs get blown out of engines before, threads & all - but that's only on the Ford supercharged SVT 5.4l where there are only 4 or 5 threads holding the plug in the manifold.

 

Thanks Diesel. A buddy of mine had the blow out problem with his build civic. I am not too worried about it at this point..... just wanted to make sure that nobody was going to respond "this happened XXX miles before my rig burst into flames" lol.

 

I have definitely seen a thread where this happened to somebody else. Might be on another forum. Definitely due to improper torque on plug.