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2003 Deville base
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258 Posts
Discussion Starter #1
What type of symptoms does a bad plenum cause?I thought it was an iac issue but I've replaced that and still have the rpms jump up when the car is put in park.drives fine however it does tend to accelerate sometimes on its own.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
It should set lean codes, effect idle, drivability, and if it's bad enough, effect starting.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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It should set lean codes, effect idle, drivability, and if it's bad enough, effect starting.
===============================:yeah: check for codes -
 

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2002 Deville
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81 Posts
i am having the exact same problem, however i think mine is still bad IAC, i bought a cheap one on ebay. might be defective... who knows
i have no plenum rips, ocassionaly sets P0507 IDLE SPEED HIGH, other than that, drives fine.
when i put it in park, i quickly shut off, due to the climbing RPM.
honestly, i just am too cheap to shell out $60 for a delphi IAC from amazon. think i lll give it a few more days to see if the IAC "relearns"...
 

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2003 Deville base
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258 Posts
Discussion Starter #5
Yea I'm not sure what mine is.every 3 or 4 times I go to put it in park my rpms jump up but then sometimes correct themselves.i did notice in park the rpms will stay at 650 sometimes but the car still almost sounds like someone keeps tapping the gas pedal a little but the rpms stay at 650.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,288 Posts
Yea I'm not sure what mine is.every 3 or 4 times I go to put it in park my rpms jump up but then sometimes correct themselves.i did notice in park the rpms will stay at 650 sometimes but the car still almost sounds like someone keeps tapping the gas pedal a little but the rpms stay at 650.
===================
have you checked for codes?
 

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1973 Cadillac Hearse, 2002 Cadillac DHS
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288 Posts
Regarding the changing/jumping RPM, when you service the IAC, you also need to clean up it's bore in the side of throttle body. I use carb and choke spray with a stiff tooth brush and a clean rag. Spray, brush, wipe and repeat until it's nice and shiny. Be sure to make sure the small passages inside are clear. I use a small piece of plastic weed whacker string to poke them out so as to not scratch anything. A dirty bore would cause the IAC plunger to stick and the idle speed to fluctuate. Both the plunger and it's bore need to be clean

@ 2002carriagetopdevil, I would suspect a dirty IAC bore might be causing your issue. Replacing or cleaning the IAC itself is only half of the equation
 

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2003 Deville base
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258 Posts
Discussion Starter #9
So is a Delphi iac a good one?I've tried 2 of the cheap no name ones online and nether one fixed my problem actuallu got worse with the cheap ones.was thinking of buying the delphi one but wanted to make sure that's the problem first
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,288 Posts
So is a Delphi iac a good one?I've tried 2 of the cheap no name ones online and nether one fixed my problem actuallu got worse with the cheap ones.was thinking of buying the delphi one but wanted to make sure that's the problem first
==================================
So is a Delphi iac a good one?
YES - Delphi is an OEM supplier -
 

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2002 Deville
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tlblack said:
So is a Delphi iac a good one?I've tried 2 of the cheap no name ones online and nether one fixed my problem actuallu got worse with the cheap ones.was thinking of buying the delphi one but wanted to make sure that's the problem first
mine arrives tomorrow, will let u know.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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So is a Delphi iac a good one?
Google "general motors delphi division".

DELPHI is/was/is/was a GM research, development, parts manufacturer, procurer division. GM/DELPHI/Lord did the development work on the Cadillac (Seville TS)/Corvette/Ferrari magnetic ride control system. It then went into later upscale Cadillacs and other GM brands.
 

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White Diamond '03 DHS (with DTS floor shift)
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:hmm: Wonder what was wrong with the old system?
Sometimes I think GM does this just to screw with us.
 

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Discussion Starter #17
When I replace my plenum should i replace any other gaskets while doing it?is there a step by step on here to replace the plenum.doesnt look to hard but would like some info
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,288 Posts
Re: 2003 cadillac deville plenum

When I replace my plenum should i replace any other gaskets while doing it?is there a step by step on here to replace the plenum.doesnt look to hard but would like some info
====================================
When I replace my plenum should i replace any other gaskets while doing it?
if you order the Dorman 911010 - it includes intake gaskets -

is there a step by step on here to replace the plenum.
yes - in the TechTips forum - here -
http://www.cadillacforums.com/forums/cadillac-tech-tips-how-fix/171319-2000-northstar-plenum-replacement-steps.html

 

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White Diamond '03 DHS (with DTS floor shift)
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Sometimes you just pay extra for a name.
Sometimes you actually do get what you pay for.
 
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