00 N* still rough idle after changing plenum, cleaning TB - Page 2
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Northstar Engines and System Technical Discussion Discussion, 00 N* still rough idle after changing plenum, cleaning TB in Cadillac Engine Technical Discussion; What do the cams cost and what's the book time for changing them and installing the software update?...
  1. #16
    SmoothTS is offline Cadillac Owners Member
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    Re: 00 N* still rough idle after changing plenum, cleaning TB

    What do the cams cost and what's the book time for changing them and installing the software update?

  2. #17
    chevyhighperformance is offline Cadillac Owners Fanatic
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    Re: 00 N* still rough idle after changing plenum, cleaning TB

    I read through this.

    http://www.caddyinfo.com/howtoroughidle.htm

    This was written in 2002. Is this information still current? Is the rough idle just the way it is?

  3. #18
    SmoothTS is offline Cadillac Owners Member
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    Re: 00 N* still rough idle after changing plenum, cleaning TB

    Quote Originally Posted by AJxtcman View Post
    OK my bosses 00 DTS with 110K had a terrible idle. I replace the cams in it and it idles smooth as glass

    I first installed the rear cams and the software patch. I needed to run the car out of the shop we got busy. I got back to it about a week later to do the other cams. The car ran about the same as it did when it came in, but the check engine light was flashing (misfires). Sure enough the front 4 cylinder all were misfiring. I replaced the front cams and the car ran so smooth you couldn't even tell it was running. I used 2003 VIN Y cams in it.
    Well I am ready to get new cams for my 2000 STS. Do you suggest I order the new replacement cams designated for the 2000? Is there any reason why you used 2003 cams for your 2000 DTS?

    How much work is it to install the cams? I looked at the service manual and the procedure seems pretty simple, except for that one alignment tool and having to flash the PCM software. Maybe I could do most of the work at home and tow the car to the dealer to have to PCM flashed?

    How many hours does it take the dealer's shop to replace the cams? Seems like a very staightforward project.

  4. #19
    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: 00 N* still rough idle after changing plenum, cleaning TB

    According to Alldatadiy the shop rate to replace all cams, no other work, is 15 (yes, 15) hours. In-house GM warranty rate is a bit less. The entire chaincase (whole front of the engine) has to come off as well as the ignition system, intake, and cam covers. The current list for the 4 cams is around $1,000. Other parts (lash adjusters, followers, chains, etc.) add more. I'll bet you're looking at $2,500, dealer.......

  5. #20
    gdmarques Guest

    Re: 00 N* still rough idle after changing plenum, cleaning TB

    I was having a rough idle and a very unusual whistling noise in my '98 Deville with N*. I was sure the noise was a bad bearing on an accessory then I read on the posts here that it might be a leaking intake manifold gasket. So I changed the gaskets and it made no difference in the noise. Finally after finding my auto stethoscope and using just the rubber hose to listen around the engine I found the noise. It WAS coming from the intake manifold however not the gaskets. For some reason at the end of the plenum on the passenger side there is a spring loaded trap door in a round recess molded into the manifold. If you pull this open with your finger (you have to raise the manifold to get at it) there is a gasket molded into the "door". I wiped this clean with a rag on both the gasket and seating surfaces, applied a very thin coating of Permatex high temp orange gasket maker and let the flap close. Reinstalled the manifold and started the engine and both the whistling noise and the rough idle were gone.

    I'll post pictures on a separate thread as I have seen many responses around the manifold gaskets themselves, but no mention of this strange valve.

  6. #21
    Ranger's Avatar
    Ranger is online now Cadillac Owners Member
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    Re: 00 N* still rough idle after changing plenum, cleaning TB

    For some reason at the end of the plenum on the passenger side there is a spring loaded trap door in a round recess molded into the manifold.
    It is called an over pressurization relief valve. in the event of an over pressurization (backfire), the valve is forced open to relieve pressure rather than having the manifold explode.

  7. #22
    SuperC's Avatar
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    Re: 00 N* still rough idle after changing plenum, cleaning TB

    Well guys, I too replaced the plenum and I still have rough idle. I am no mechanic and replacing the plenum was not an easy job. I think I am gonna have to see a pro for this one.
    -C

  8. #23
    Murphyg's Avatar
    Murphyg is offline Cadillac Owners Connoisseur
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    Re: 00 N* still rough idle after changing plenum, cleaning TB

    Quote Originally Posted by SmoothTS View Post
    .................................................. .... The only other thing I can think of is to have my fuel injectors cleaned and maybe change the fuel filter.
    So how did that work for ya ?

    Just had that done on my 01. Made a difference.
    Also did it all on the wifes 99 Bonneville......and what a "major" difference.

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