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2003 seville sls
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32 Posts
Discussion Starter #1
I've read on this site that the plenum gasket cause these issues that is the only code i get also when i sprayed tb cleaner by the gasket it caused the idle to change just want to make sure its that gasket before i get the parts and tackle that job this weekend
 

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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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20,219 Posts
Re: 03 sls code p0507 idle is goofy/ bad gas mileage

check for Diagnostic Trouble Codes -

if you don't know how - go here and read the ENTIRE post -

http://www.cadillacforums.com/forum...ncluding-1985/138257-how-pull-codes-dtcs.html

if you have any codes - post them here -
ALONG WITH THEIR DEFINITIONS -
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a torn/split plenum boot usually splits in the groove at the bottom -

the defective plenum boot will usually set a P0171 AND P0174 codes -

P0507 - is HIGH IDLE SPEED -
while a vacuum leak could affect the idle speed -
I would check the Idle Air Control valve for a buildup of carbon -
also check the throttle body for a buildup of crud -
it could actually prevent the throttle plate from closing -
 

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Registered
2003 seville sls
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32 Posts
Discussion Starter #3
Re: 03 sls code p0507 idle is goofy/ bad gas mileage

0507 is all that comes up and when i sprayed that tb cleaner toward s the bottom of the gasket idle fluctuated is the only way to check the plenum gasket is to take the intake off?
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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20,219 Posts
Re: 03 sls code p0507 idle is goofy/ bad gas mileage

0507 is all that comes up and when i sprayed that tb cleaner toward s the bottom of the gasket idle fluctuated is the only way to check the plenum gasket is to take the intake off?
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is the only way to check the plenum gasket is to take the intake off?
NO - run your finger around and under it -
like I said - it USUALLY splits in the groove - at the bottom -

but if P0507 is your only code - the plenum boot is probably NOT your main issue -
 

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2003 seville sls
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32 Posts
Discussion Starter #5
Re: 03 sls code p0507 idle is goofy/ bad gas mileage

Iac valve is that where i should start don't have a scan tool any suggestions on how to test it myself should i just replace it
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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71,032 Posts
You don't need a "scan tool" - your car has its own built-in code reader/scanner/memory. Study the correct model/year section of the sticky post ^^^ "How to pull codes". practice, write down all codes found and whether each is Current or History. return to the sticky and open the link with "obd2" in the address - this takes you to a master Index with links to definitions of all P,B,C, and u codes. Decipher any codes found and post it all here. Also, read the entire page along with the Master Index.

Your engine uses an Idle Air Control solenoid and plunger, not an ISC. The IAC is a high-dollar item to replace for no reason. Disconnect the electrical connector, remove the 2 screws (or bolts - models vary) and pull the IAC out of its bore. Clean the top hat and bore with throttlebody cleaner and lint-free rags. Smear a drop of engine oil on the O-ring and install the IAC.

Poor gas mileage may be caused by a faulty Fuel Pressure Regulator - it's on the right (rear) run of the fuel rail - a domed unit with a vacuum line attached. Carefully remove the vacuum line - any raw fuel in there ? if so, replace the FPR. Your car should get 12 - 16 mpg city traffic, 16 - 20 mpg suburban, 27 mpg long run highway trips. 87 octane Top Tier gasolines. DO NOT use snake oils or magic potions in the fuel or oil.

For a look at your plenum, the part numbers, and every piece associated with its replacement, look in my picture albums. Click my username, open the profile. Left column, 2 albums, 6 pages of stuff for our cars. For techniques and procedures, search through the pages of Discussions: Cadillac Tech Tips and use Google - "cadillac forums seville plenum replacement" or "cadillac forums seville intake manifold plenum duct".

You might want to read the entire Cadillac Technical Archive up ^^^ in the top black bar. There is info there that you NEED.
 
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