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2007 DTS
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63 Posts
Discussion Starter #1
I might have to change plenum boot on my 2004 Cadillac deville,, past week has been low idle in morning and after driving 20 miles to work i park and its idle high 2000+rpm,, i already replaced the pcv dirty piping vacuum i found leaking,replaced air filter,fuel filter, took off the iacv and cleaned with electro cleaner and i cleaned throttle body,, .. So today did same idling 3000rpm when i got home, i hurried popped the hood and sprayed the plenum boot with throttle body cleaner, and as im spraying on the boot it idles down n i can see it sucking the throttle body cleaner,,, so i guess im gona have to replace plenum boot,, Anyone out there what u think got any advise for me??
 

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White Diamond '03 DHS (with DTS floor shift)
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86,793 Posts
Usually if you have a ripped plenum duct you will get an SES light accompanied by a P0171 & P0174 code and the RPM will INCREASE when you spray TB cleaner on the rip.
 

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2007 DTS
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63 Posts
Discussion Starter #4
I did clean throttle body and iac , and when rpms are at 2500rpm in park i sprayed throttle cleaner on top the plenum boot and and i hear and see it sucking and for that breaf moment it idles down not up

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When we scanned it only got P0171 and p0174 and afew other different codes like map and maf

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But no SES code

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If u say rpm shuld decrease when i spray boot,, what can it be then im lost here
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,513 Posts
You sprayed this plenum, right ?

........... and the TB cleaners/choke cleaners are extremely flammable, so if they're pushed into a vacuum leak it normally increases engine speed = more fuel.
 

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2007 DTS
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63 Posts
Discussion Starter #6
Yea thats wat i sprayed n it was sucking the TB spray,,gona change the plenum this weekend
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,513 Posts
OK - more pictures in my albums and procedures in Tech Tips.

Google "cadillac forums northstar intake manifold plenum replacement" or something close, always preceded by "cadillac forums .............".
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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If you changed the plenum duct and it's still sucking air from the top, check the clamp. You may not have it seated or clamped properly.
 

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2007 DTS
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Discussion Starter #11
Ranger i replaced plenum boot it was cracked all around bottom, so i put new plenum boot, intake orings,fuel injector orings and everything back together, so i start up car sprayed plenum and throttle body with TB cleaner and no leaks but after 5 minutes rpms still high as high as 3000 rpm ,, idk what else can it be??? Help me please
 

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2007 DTS
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63 Posts
Discussion Starter #12
FINALLYYYYYY BACK TO NORMAL AT 700 RPM MY CADY,,, ended up having to replace the temperature coolant sensor wich was causing HIGH RPMS ,,unbelievable,, its was a b##! To get to but i got it,,,
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,793 Posts
ECT sensor cause high RPM's? :hmm: I would not have suspected that. :noidea:
What led you to that?
 

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2007 DTS
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63 Posts
Discussion Starter #14
My nephew,, i calld him n told him wat iv done n wat car is still doing after it warms up n he told me change the coolant temperature sensor,, cause acouple weeks ago was fixn a cady with same problem and as soon as replaced that sensor problem solved,, and it makes sense because sensor had malfuction and its basically telling the computer car engine still cold and makes computer go crazy so it stays accelerated ,,, problem solved $20 more dollars later for the sensor and lucky i have a skinny arm cause that sensor was in a veryyyy tight spot,,, unbelievable

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Now after everything i replaced i cant even tell the engine is running and check engine light is not on no more ,, good deal n thanks Ranger for advise of plenum boot ,,good deal
 

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My nephew,, i calld him n told him wat iv done n wat car is still doing after it warms up n he told me change the coolant temperature sensor,, cause acouple weeks ago was fixn a cady with same problem and as soon as replaced that sensor problem solved,, and it makes sense because sensor had malfuction and its basically telling the computer car engine still cold and makes computer go crazy so it stays accelerated ,,, problem solved $20 more dollars later for the sensor and lucky i have a skinny arm cause that sensor was in a veryyyy tight spot,,, unbelievable


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Now after everything i replaced i cant even tell the engine is running and check engine light is not on no more ,, good deal n thanks Ranger for advise of plenum boot ,,good deal
If the sensor was failing low, it would also make the gauge read off low. I believe that sensor is the only input to the pcm for coolant temperature. Was it reading low on the dash?
 

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2007 DTS
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63 Posts
Discussion Starter #16
No temperature on dash was normal,,ever sense i replaced the ECT sensor rpms been normal
 

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2007 DTS
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Discussion Starter #17
Hello need some opinions on some codes that came up now, after acouple months running good started a misfire when im passing another vehicle and check engine light came on so i scanned it and got these codes P0102 maf, P0107 i guess has to do with maf sensor, P0121 tps, P0171 fuel trim bank one condition, P0174 fuel trim bank two condition, P0300 cylinder misfire detected-random cylinder, P0420 catalyst efficiency low bank 1, P0506 IAC circuit condition or idle speed higher/lower than expected, P0507 IAC circuit condition or idle speed higher/lower than expected, P0520 engine oil pressure sensor, P1372 crankshaft position sensor A-B correlation,,,.. I need an opinion on this i know its only 1 thing causing all these codes n im pushing towards maf sensor o throttle position sensor,, i already replaced IAC valve, all vacuum lines, plenum boot, fuel filter ,,, anyone can help me out before i go buy all rest on sensors,, thanks
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Too many random codes to point to so many simultaneous failures - UNLESS you have engine-to-PCM wiring harness connector problems.

Maybe even something as simple as one or two engine to body ground cables are compromised.

Wiring and connector tracing are unpleasant but necessary .................
 
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