2003 2004 2005 2006 major engine failure cause
 

I've now owned two each 2003 Montero Limiteds with 3.8L. I think the same motor design was in all 4 years (03 thru 06). I figured it out from a forum post I can't find anymore.

Both of my Monteros around 165,000 miles lost several intake butterflies that are accessible when you remove the plummy plummy...haha the plenum.

If you haven't already I suggest you remove them too before they ruin your motor. The come loose, because they're only held on by 2 dinky screws. They should have been welded, or something better...but live and learn.

Removing them doesn't seem to effect operation at 6,500 to 11,500 feet above sea level, where I live.

A possible lawsuit? I bet many of these came loose much earlier than 165,000 miles and blew motors up. That's just when I discovered mine loose. They looked to have been there for a few thousand miles. They were partially melted and broken in half. All screws and some molten metal were ingested and likely did some harm to my motors. But mine still run...tough or lucky, I got lucky. They do so leak or consume about a quart of oil every 1,000ish miles.

FYI

Thank you - I just asked about this in another post where you mentioned butterflies. I'll have mine checked out.