99 DeVille D'elegance
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Northstar Engines and System Technical Discussion Discussion, 99 DeVille D'elegance in Cadillac Engine Technical Discussion; Hello everyone! Got myself into a BEAUTIFUL 99 DeVille D'elegance with 113k about a month ago and I must say ...
  1. #1
    mcss88 is offline Cadillac Owners Member
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    99 DeVille D'elegance

    Hello everyone! Got myself into a BEAUTIFUL 99 DeVille D'elegance with 113k about a month ago and I must say it's quite a change from my 99 base that I junked last summer. I've been reading past posts on the forum and trying to soak up as much knowledge as I can and had a few questions that I didn't see mentioned.

    I was inspecting the motor the other day (P0300 Random Misfire when going up hills, throws the code in the EXACT same place on the hill where my 99 Bonneville threw it, turns out it needed a set of wires. I know the 3800 and Northstar are two VERY different engines, but still) and I noticed that my plugs are VERY warn, I plan to replace with the correct OEM AC Delco plugs. I also noticed that the plug wires were rubbing on the front (and probably rear) cam cover. They don't appear to be warn through but who knows. Might as well replace them. I'm wondering if anyone else had this rubbing problem? The wires on the car are AC Delco with the plug numbers on them (original?) I had planned on putting a piece of fuel hose around the new wires where the old ones were rubbing. This shouldn't be a problem?

    I also noticed severe carbon buildup on the top of the pistons. I plan on doing a few real good WOT runs as described in the technical archive.

    I also noticed a very rusty tower on one of my coils. I hit it with a wire brush but it didn't seem to help any. When I pull the ICM to do plugs I plan to clean it thoroughly and coat with dielectric grease. I checked resistance of the coil packs and they were all pretty darn close 5.xx on 20k ohms.

    The car is also throwing a U1255 - Class 2 Comm Failure. Everything works on the car with the exception of the power antenna. Could this be related to the misfire?

    I was planning on cleaning the TB and EGR as well while I have her taken apart. I have a honeycomb looking... thing - for lack of a proper term- at the TB Inlet. How is that removed? Also, I know I've read it but what should I use to clean the TB? Electrical Parts cleaner as to not interfere with the MAF and EGR Valve?

    Thanks for your assistance in advance. I'll be posting some pics of my beauty as soon as time permits.

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 99 DeVille D'elegance

    The wires on the car are AC Delco with the plug numbers on them (original?)
    Yeah, those are original.


    The car is also throwing a U1255 - Class 2 Comm Failure. Everything works on the car with the exception of the power antenna. Could this be related to the misfire?
    Probably not.


    I have a honeycomb looking... thing - for lack of a proper term- at the TB Inlet. How is that removed?
    It's called an air flow straightener. If I remember correctly I used a small wire bent at a 90 degree angle and just pulled gently around the perimeter. I recall a retaining ring, but I think that was on the 3800, but look close to be sure. Keep in mind that it is very delicate and bends easily so be very gently.

  4. #3
    mcss88 is offline Cadillac Owners Member
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    Re: 99 DeVille D'elegance

    Thanks for the quick reply, Ranger. From what I've read the u1255 could be a whole bunch of things. Its always current. Is it one of those codes I just plain shouldn't worry about unless something else pops up?

    I took a look under the hood after my post and it looks like the TB is on the engine side of the MAF? (I thought the other way around for some reason) so I would take the MAF off with the airflow straightener to get access to the TB I would think. Either way once I get time to tear into it it'll be pretty obvious I'd think.

    Thanks again!

    ----------

    Just found the thread on cleaning the tb. Should be interesting to see what happens when she gets all cleaned up and tuned up. Hoping to get to it later this week.

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 99 DeVille D'elegance

    Yeah, unless you are having other problems or have other codes, I'd just ignore the U code, but I am surprised that it is current.

    They keep moving the MAF sensor, so I may have been thinking about a different year (or the 3800). According to this diagram, yours (#1) is bolted to the TB so disregard my bent wire tool. The air flow straightener should be part of it. Just unbolt it.

    http://www.gmpartsgiant.com/Page_Pro...074&SortKey=30

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