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Tim West
Tim West, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 4638
Experience:  Ase certified service manager
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01 cadillac deville has a code p0171 and p0174 lean codes

Resolved Question:

01 cadillac deville has a code p0171 and p0174 lean codes
Submitted: 6 years ago.
Category: Cadillac
Expert:  Tim West replied 6 years ago.
Thanks for visiting Just answer,
These codes are common when you have a vacuum leak.
With the engine idling, add propane to the front of the intake manifold. If the engine reacts, check for a leaking anti-backfire valve. This is a spring loaded plate at the end of the intake plenum. Check the boot between the throttle body and the intake for air leaks.
These are the most common reasons for these 2 codes.
can you check it out and get back to me?
Customer: replied 6 years ago.
if i spray carb cleaner in front of intake behind the ps pump the engine races is that where the anti backfire valve is? and do they sell that at part store or is built in to the intake
Expert:  Tim West replied 6 years ago.
That's right, should be on the passenger side of the engine (opposite of the throttle body). You have to get the part from the dealer. It's called the anti-backfire valve. Or backfire relief valve. It's designed so the intake will not blow up during a backfire.
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