1997 Dakota 3.9L w/ 170k miles. Sorry in advance; for me to explain
this thoroughly will require a lengthy post.
Two years ago I did my 150k mile (and most recent) complete tuneup,
and when I went to remove spark plug #5 at that time, it just about
wouldn't budge. I don't recall having any such spark plug problems
before... but for some reason at 150k miles that #5 was a bear to
remove. I did get it out, and to my surprise the threads on the plug
looked ok w/ no extra metal or chewed threads. Then when I went to
put the new plug in (with anti-seize), it wouldn't finger tighten past
about 1 or 2 revolutions. I carefully tightened it the rest of the
way with a socket, and it was rough going but I got it tightened and
never had anymore problems with it... until now.
Over the past few days I've noticed a definite misfire under
acceleration, but it isn't constant... it comes and goes. Well today
I pulled a P0305 #5 misfire code. I put new wires on and it made no
difference. I inspected inside the distributor cap and everything
looks uniform (ie #5 doesn't look any different than the others). So
I hesitantly tried to remove plug #5, and just like last time, it's
really hard to turn. I backed it out about 1 revolution and then
chickened out - it wasn't getting easier, it actually started getting
harder to turn.
I am fairly (but cannot be completely) sure that I never cross-
threaded it - I always finger tighten the plugs. I'm perplexed
because the plug threads looked ok after I fought to get it out last
time. I've come up with 4 potential explanations for this new
1) Some plug holes just become stubborn, and maybe I inadvertantly
damaged the plug's insulator while trying to get that new #5 installed
last time, and maybe it's now starting to bleed voltage in a short
circuit on occasion. This is my best case scenario.
2) Maybe the threads did get damaged or crossed despite my finger
tightening rule and despite the threads looking ok last time I had the
plug out after fighting with it. Rust or crud could have hitched a
ride into the threads 2 tuneups ago and welded the plug in place. The
idea here is that it's losing compression or something due to screwed
up threads. (Can damaged threads do that? Maybe time for a
3) Could be coincedental. Maybe injector #5 is clogged or bad.
4) Could be much worse... worn or damaged valve or seat, blown head
gasket, cracked head, etc.
So I suppose my question to you all is, does it sound like the "stuck"
#5 plug could be related to my new #5 misfire? Which, if any, of my 4
explanations sounds most valid? Any suggestions? I'm scared stiff at
the thought of trying to remove that plug right now.