Spark Plug and Wire Change Summary

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 4 of 4
Northstar Engines and System Technical Discussion Discussion, Spark Plug and Wire Change Summary in Cadillac Engine Discussion; I can't feel my toes..... To thank everyone who have been helping over the last many weeks on my misfire ...
  1. #1
    powerglide's Avatar
    powerglide is offline Cadillac Owners Connoisseur
    Join Date
    Sep 2003
    Hermosa Beach, CA

    Thumbs upSpark Plug and Wire Change Summary

    I can't feel my toes.....

    To thank everyone who have been helping over the last many weeks on my misfire problem, I'm gonna post a summary of the jobs for future reference.

    P0300 Misfire 1998 Deville 72.5K Miles
    Jan 27 2004 Manhattan

    First off, I took my DIEHARD GOLD battery to sears and got it replaced nocharge or paperwork. I took it out and installed the new at the sears parking lot , it was snowing a bit and very cold but the job was about 10 minutes long. There are about 5 bolts around the top of the battey plate that neeed to come out before you get to the battery.
    Tools needed, socket wrench set
    Suprisingly made a huge difference but it wasn't fixed....

    Dealership wanted about 500 bucks or so to do a Sprk Plug and Wire change that includes parts and labor. I refused and came to the forum.
    After some feedback, I ordered through Although I didn't have the part number I just wrote them an email with what I wanted to do (plus VIN #), the next day they replied with a list of part numbers which I used to order through their website. I went with all ACDELCO orginial parts, as recomended by manufacturer but more importantly the experienced folks on this forum. 8 plugs, 4.22 a piece, wire kit was 75.27$ (they list for 150 at the dealer), plus some shipping like 15 bucks or so basically about 110 bucks and change. I bought a three piece socket extension bar from sears at 9.99 to get to the socket all the way down to the spark plugs. The parts arrived in about a week and I got a free hat too! Thanks gmpartsdirect.

    Turns out the plugs are not PREGAPPED, and needed to be gapped. I however did not have a gapper and was stuck for time so I bit the bullet and used them right out of the box. (probably not wise)

    On the streets, curbside Manhattan, 3PM lite snow.
    I went out there, removed the plastic engine cover and started.
    First I pulled the front four plugs and replaced them one at a time, after each was replaced I put the OLD wired back ontop of the new plugs just so I can keep them straight (although my wires were pre-labeled)
    Then, I went to the back of the engine and removed the ignition coils box (?) I took four bolts holding down the small rectangular box to get to the rear plugs. I did not have to remove the strut tower braces, the box slid out of the way no problem. I replaced the plugs on the back.
    Once all the plugs were new, I started on the wires, one at a time. All the wires on my new set WERE NOT labeled, so I had to figure them out by comparing the length of the old wire to the new one to find the correct wire for the cylinder. (easy)
    One at a time I loomed them through their original location.
    Made it look nice and bolted the coil box back in place. ****Note, one of the four bolts holding down this ignition box has a ground wire for the engine connected to it. Make sure you don't forget to put this wire back on the bolt before putting the coil box back.
    Thats pretty much it.
    I didn't have any thread lock/dielectric grease so none was used. (the new plugs had dielec grease in them) Put the cover back on and it fired right up, runs ALOT better now, haven't taken it on the highway yet but the way the revs climb so fast (responsive) was a little amazing.
    Its 5Pm or so, its dark and cold now, the whole job took less than 2 hours, on the streets, cold as hell, all in a warm well lit garage with an extra hand its should be hour TOPS. The dealer was gonna charge for 2.5-3 hours.....saved 300 in labor and about 100 in parts.

    Great DIY, highly recomended doing this on your own and as a tune up even if your car isn't running weird, change these baby's out and it will make a huge difference. My plugs were ALL pretty black and fouled depite my WOT runs and often crusing at 85 MPH.

    My favorite part of the job was when the car started!
    The worst part was probably tremoving the coil box bolts...or maybe the looming. Actually all pretty easy and smooth.

    On my mind.......
    1) gap, although I didn't gap it and its fine, I know it could be optimized....hope it doesn;t cause problems
    2) looming.....I loomed most of the wires through the original spot but some of the plastic wire clips got broken when removing....some of the wires may be contacting the block and hope it doesn't melt or wear through. (Any comments about this someone?) I think I will double check the wires in the morning light to see if I can tape or insulate some more...( too dark...too cold)

    I guess, thats it. I just wanted to take the time to write this up to thank everyone and for future reference for current and new members.

    Hope this helps someone somewhere sometime.

    Best Luck

  2. Remove Advertisements

  3. #2
    zonie77 is offline Cadillac Owners Connoisseur
    Automobile(s): 94 ETC,97 STS
    Join Date
    Sep 2003

    Re: Spark Plug and Wire Change Summary


    Glad it worked and the car runs better !!!!

  4. #3
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Fort Lauderdale, Florida

    Re: Spark Plug and Wire Change Summary

    The new plugs may have helped...but...those plugs should last WAY beyond 100K. My guess is that there is something else wrong that caused the black plugs and fouling. The plugs should run almost pure white even in stop and go driving and especially if you stood on it a lot.

    Did you check the fuel pressure regulator for fuel leaking past the diaphragm?? That is the simplest thing to check that could cause excessive fuel and black plugs and fouling like you describe.

    Simply pull the vacuum hose off the fuel pressure regulator while the engine is idling and watch the nipple on the fuel pressure regulator for signs/smells of fuel. There should be none. Any sign of fuel at the vacuum nipple on the FPR after 5 minutes or so....replace it.

  5. Remove Advertisements
    Cadillac Forums

  6. #4
    powerglide's Avatar
    powerglide is offline Cadillac Owners Connoisseur
    Join Date
    Sep 2003
    Hermosa Beach, CA
    Thread Starter

    Re: Spark Plug and Wire Change Summary

    Just got back from my 'test drive' 900 miles.
    The car ran smooth and strong, it almost felt like a 'VTEC' engine.
    I never detected any rough idling except a little hint during cold start, sub zero.

    You may be right about something else being out of whack.
    I attached a picture of my old plugs.

    I haven't checked for fuel at the nipple yet.....

    BTW: There is this "vacuum leak like" sound (high pitched whistling) coming from near the intake manifold or power steering (not sure at all where the sound is from). Its been making it for a couple months now. I read elsewhere on this forum that a leaking intake manifold was causing misfiring and a whistling noise. Does this ring a bell for anyone?
    Attached Images

  7. Remove Advertisements
    Cadillac Forums

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

What Cadillac(s) do you own? (Or type NONE)

Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts