Owner's book · not a shop

Open Hood

Know the car. Then the window. Factory specs in plain English — don't authorize until you can say this at the counter.

No car yet Try the demo · 2003 Honda Accord

Owner tools

Lab desks

Fix Finder · 19 aisle tickets

Code or symptom

Type what the scanner printed, or the smell / squeal. We name the jobs, then the boxes — and we hold the ones you should not throw.

Walking the aisle…

Fix Finder · 19 aisle tickets

Code or symptom

Type what the scanner printed, or the smell / squeal. We name the jobs, then the boxes — and we hold the ones you should not throw.

Open aisle

P0300 · Diagnose first

Random / multiple misfire

The computer counted misfires on more than one cylinder. That can be plugs, coils, a vacuum leak, fuel, or a failing coil driver. A flashing light means stop driving — raw fuel is washing the cat.

Do not throw a coil kit from P0300. Name the cylinder that is dead, then the part that failed the test.

DIY

Look, then stop

You can read pending codes (P0301–P0308) and look at plug condition. Swap-test is shop or experienced DIY.

If the light is flashing, stop driving. That is catalyst-poisoning territory.
Write every code, including pending P0301–P0308. Those name the hole.
Do not buy four coils because the aisle had a kit.

Tools: Scanner · Flashlight

In the aisle

What they will ask

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
Coil-on-plug vs a shared coil pack changes the box they pull.
Iridium, platinum, or copper plugs?
They will ask — not on the hook yet
Gap and heat range are engine-family parts. The wrong plug is a new misfire.

Parts aisle

Boxes on the hook

Search for year / make / model not on the hook. Not stock. Not TecDoc.

Ignition · bin IGN-1

Spark plugs (set)

If they are due or look fouled. Not automatic from P0300.

Query: spark plugs

Ignition · bin IGN-2

Ignition coil (the dead hole)

One coil if a swap-test moved the misfire. Not a four-pack by default.

Query: ignition coil

Ignition · bin IGN-3

Plug wires (if equipped)

Coil-on-plug cars do not have a wire set. Ask first.

Query: spark plug wires

Related: Plugs · P0420