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One cylinder misfiring and a code like P0302 usually mean a valve has stopped sealing. The fix is this 16-piece intake and exhaust valve kit for the 2.0L Hyundai Elantra and Kia Soul — eight intake and eight exhaust valves in one box.

What one bad valve does to one cylinder

Your 2.0L head breathes through sixteen valves — two intake and two exhaust per cylinder. Compression exists only while all four seal shut.

Valves fail in two ways. A burned valve wears a notch into its face, usually where a seat leaked or a hot spot burned through.

A bent valve stops closing at all — the classic aftermath of a snapped or jumped timing belt.

• The weak cylinder fires late or not at all, so the crank dips once per revolution.
• The computer counts that dip as a misfire and stores a code.
• Unburned fuel flows on into the exhaust and overheats the catalytic converter.

P0300 and the codes that point here

A DTC — diagnostic trouble code, the numbered fault stored after a failed self-check — is your first clue. The misfire family:

• P0300 — "random or multiple cylinder misfire." More than one cylinder is weak, or the computer cannot tell which.
• P0301 to P0304 — cylinder-specific. The last digit names the cylinder: P0302 means cylinder 2.
• Flashing check-engine light. That is an active misfire dumping fuel into the catalyst — stop driving hard.

One weak cylinder points at one valve, one injector, or one coil. Two or more point at timing, a head gasket, or fuel delivery.

Step one: the compression test

Compression is the test that convicts a valve. Warm the engine, pull all four spark plugs, and hold the throttle open while you crank.

1. Disable the ignition and the fuel injectors so the engine cannot fire.
2. Screw the gauge into cylinder 1 and crank until the needle stops climbing.
3. Record all four cylinders, then repeat with a teaspoon of oil in each bore.

The Hyundai spec for this 2.0L is 1,420 kPa, about 206 psi, at 250 rpm or more with a charged battery. Below 1,270 kPa (about 184 psi) a cylinder fails, and cylinders should stay within about 98 kPa.

If the wet reading stays just as low, the leak sits above the piston — valve or head gasket, not rings.

Step two: leak-down names the leaking valve

A leak-down test presses compressed air into the dead cylinder and measures how much escapes. Then you listen. Each escape route names the failed part.

• Air at the intake or throttle body → an intake valve is not seating.
• Air at the tailpipe → an exhaust valve, the most common finding by far.
• Air at the oil filler cap → worn rings or a scored bore, not a valve.
• Bubbles in the radiator → head gasket or a cracked head.

Single-digit leakage is a healthy engine. Past 20 percent needs a plan, and past 30 percent is a head-off repair.

Why these valves bend: the timing belt

This 2.0L is an interference engine. Pistons and open valves share the same space at different moments, and only the timing belt keeps them apart.

When the belt slips a tooth or snaps, the camshafts stop while the crank keeps spinning. Pistons then slam into whatever valves hang open and bend them.

Hyundai's interval for this belt is about 60,000 miles. The Hyundai-Kia 2.0L timing belt and water pump guide covers the interval and the parts to replace with it.

• Belt already overdue and one cylinder suddenly weak → suspect bent valves first.
• Head is coming off anyway → budget the full sixteen-valve set, not one valve.

Doing the valve job

The head has to come off for this repair. Sixteen valves means sixteen springs, seals, and seats — keep every part in order.

1. Remove the head, compress each spring with the Hyundai valve spring compressor (SST 09222-28000), and lift the valves out.
2. Check the gasket surface for warpage against the 0.05 mm (0.0020 in.) limit, and have it machined flat before reassembly.
3. Lap each new valve into its seat until a continuous gray ring shows, and fit new stem seals.
4. Refit the head with new bolts torqued in sequence, then set the belt timing marks exactly.
5. Recheck compression on all four cylinders before you close the covers.

Keep the two valve types apart on the bench. A longer valve in the wrong seat will hit a piston.

Some CVVT heads use solid lash adjusters — the buckets that set valve clearance — so measure their clearance before the camshafts go back.

Related parts for the same engine bay

These engines share smaller failures that show up as idle and start problems. Match them to your symptoms:

• A rough idle that survives a healthy compression test often lives in idle control — the idle air control valve for the 2010-2011 Kia Soul 2.0L is a short swap on those cars.
• Working on a 1.6L engine? The shelf also carries the 22212-26050 exhaust valve set for the 2001-2011 Hyundai Accent and Kia Rio and the 22211-26600 intake and exhaust kit for those engines.
• Past 150,000 miles on the original sensor? Pair the job with a fresh camshaft position sensor, OE 39350-23700.

All of these sit in the engines and engine parts collection, alongside valves, sensors, and gaskets.

Frequently asked questions