Owner's book · not a shop
Open HoodKnow the car. Then the window. Factory specs in plain English — don't authorize until you can say this at the counter.
Stamping the aisle…
Fix Finder · P0171
P0171 · Diagnose first
The computer is adding fuel because the exhaust looks lean. Unmetered air (vacuum leak, cracked hose, dirty MAF) beats a new oxygen sensor most days.
Do not throw a MAF or an O2 from P0171. Find the hiss or the fuel trim number first.
DIY
You can listen for a vacuum hiss and check the air-box lid. A smoke machine is shop gear.
Tools: Ears · Flashlight
In the aisle
The parts person does not start with a SKU. They start with the engine and whether it is 2WD or 4WD. Answer from the bay ticket when we have it.
Which engine?
They will ask — not on the hook yet
Intake boots and PCV valves are engine-family parts.
Parts aisle
Search for year / make / model not on the hook. Not stock. Not TecDoc.
Air · bin AIR-2
A cracked boot after the MAF is classic unmetered air.
Query: air intake hose
Emissions · bin EMIS-1
A stuck-open PCV leans the idle.
Query: PCV valve
Hold
Sensors · bin HOLD
HOLD until trims and a leak check say the meter is lying.
Query: mass air flow sensor