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About bilysinger

  • Rank
    Observer (3-9 posts)

Previous Fields

  • Car Model and Year
    Deville 2003
  • Engine
    Northstar 4.6L V8 (LD8/L37)
  1. Sure would like to know what vacuum line this is . I have p171 and p174. Can hear what I think is a vacuum leak, dogged if I can find it. FRUSTRATED Bet it is the plenum, ( a corrugated rubber hose with a 5" Diameter to connect the throttle body to the intake manifold. unless you take apart the top of the engine to get to it you'll never find where the intake leak is. even visual inspection is not enough, you need to probe all the hose with a screw driver to open up any slits hidden on the hose.I know, had to take mine apart twice, to find the leak.
  2. Actually the difference is, the rear has 2 threaded holes to hold the air pipe going under neath the car via the firewall but the gentleman is right, besides that there is no difference except the color.
  3. Yea but it idles good when in neutral only rough idle in drive. and no codes EGR is disabled in neutral and park. I know cleaning EGR valve and some passages is not fun on a Northstar. Can you drive for a while with disabled EGR to see if idle smooths out? You can either disconnect EGR solenoid or pull a vacuum line from the EGR valve (do not forget to plug that line with something like a screw). Some EGR related codes may be set if you disable it. I also went through this scenario. These rubber plenums are of poor design. They used a sub grade of rubber when manufactured. It took me 2 tries to find a 5" slit in the plenum. it was within one of the corrugations and hiding from my sitght. But, when I bought a new one from the dealer they had 5 more in stock. Must be that it's a common cause and to have that many in stock is not typical for this item meaning, THEY ALL GO BAD WITH AGE. Thanks Cadillac for using poor rubber to attach the throttle body to the intake manifold.