I Have A 1990 Supercab 2wd With A 4.9 And A 5 Speed. When I First Got It I Changed The Plugs And Noticed The Old Plugs Were Loose. (Like 3 or 4 Were Finger Tight) I Put New Ones In And Was Rollin Smooth For A Month Or Two Till I Had ECM Problems. Mine Took A Crap And I Searched Salvage Yards High And Low For The Correct One. (It Has "CB" As The Last 2 Letters In The Part Number) I Ended Up Running For Like 3 Weeks With A Spare ECM From My Brother's 1993 Taurus 3.8 V6. My Truck Ran Rough And Was Weak On The Low End But Could Smoke The Tires Off With Higher RPM's. LOL. I Recently Got The Correct ECM (For An Automatic) And My Truck Still Ran A Little Rough But Much Better Than With The Bad ECM And The Taurus ECM. Until I Went To Give It A Tune Up. When I Went To Change Plugs I Noticed They Were Really Loose. So Instead Of Changing Them I Just Tightened Them Up And Took A Drive. All My Power Was Back And Not One Miss Or Hesitation And 20 MPG Again. But My Question To You Guys Is Why Were My Plugs Loose. I've Changed Plenty Of Plugs In My Lifetime And Have Never Had A Set Back Out On Me. I Dunno. Any Input Would Help. Thanks.
Yeah I have had plugs back out before, usually in a cast head application. If you torque the plugs properly they will not back out, though that can be fun with the room given on these though they are loads better than my s10 was.