Tools & supplies
- Basic metric socket set (8–14 mm), ratchet, extensions
- Screwdrivers (flat & Phillips) and small pick set
- Hose‑clamp pliers or long‑nose pliers
- Pliers/wrench for small bracket bolts
- Replacement breather/PCV hose (high‑temp rubber or OEM), replacement grommet(s)
- New PCV valve (recommended), small worm clamps or OEM clamps
- Torque wrench (if valve cover bolts are disturbed)
- Clean rags, gloves, eye protection
- Shop vacuum or handheld vacuum pump (for checking PCV vacuum)
- Crankcase pressure gauge / manometer or inexpensive gauge adapter that fits oil‑filler neck (for blow‑by test)
- Compressed air (optional, low pressure) for clearing tube — use caution
- Parts cleaner / carb cleaner (optional)

Safety precautions
- Work with the engine cold unless a test requires it running. Hot metal & oil cause burns.
- Wear safety glasses and gloves. Keep loose clothing/jewelry away from moving parts when engine must be run.
- If you will start the engine to test, keep hands/tools clear of belts, pulleys, fans.
- Use low pressure if you blow compressed air through hoses to avoid forcing debris into engine.
- Ventilate area when using solvents.

What the “blow‑by tube”/PCV system is and why service it
- The blow‑by/vent tube routes crankcase vapors from the valve cover/oil separator back into the intake (or to the air cleaner). Over time hoses become brittle, grommets fail, PCV valves stick, or the tube plugs with sludge. Replacing hoses/grommets and the PCV valve restores crankcase ventilation and prevents vacuum leaks or oil leaks.

Step‑by‑step: remove, inspect, replace (VG30E & KA24E are similar in concept)
1. Locate the tube/PCV components
- On both VG30E and KA24E: look at the valve cover(s) for a short metal stub or rubber boss with a hose leading to the intake/plenum or air cleaner. The PCV valve is usually inline in that hose or seated in the valve cover.

2. Prepare vehicle
- Park level, set parking brake, engine cool. Disconnect negative battery if you will remove ignition components or when doing unrelated electrical work. Have rags/catch pan ready for oil drips.

3. Remove intake obstacles
- Remove any air intake tubing or engine covers obstructing access to the valve cover breather hose and PCV valve so you can reach both ends of the hose.

4. Remove hose/clamps
- Use hose‑clamp pliers or a screwdriver to loosen clamps on both ends. Twist the hose while pulling to break the seal. If hose is stuck, use a flat screwdriver gently—don’t pry on the valve cover plastic/metal excessively.

5. Inspect PCV valve and grommet
- Pull the PCV valve from the valve cover. Shake it — a working PCV will rattle. If sticky, replace. Inspect the rubber grommet in the valve cover; if it’s hard or cracked, replace it. Inspect the metal tube/grommet boss for corrosion or damage.

6. Remove old hose and clean fittings
- Remove the hose completely. Clean the valve cover boss and intake connection with a rag and parts cleaner. Remove any sludge from inside the hose connection with a pick or rag.

7. Decide on replacement parts
- Replace hose (high‑temp vacuum hose), PCV valve, and grommet as a minimum if aged. Replace clamps if corroded. If the valve cover boss/grommet is damaged, you may need a valve cover gasket service or a replacement valve cover grommet.

8. Fit new grommet/PCV
- Install new rubber grommet into valve cover (press in fully). Insert new or tested PCV valve into grommet until it seats. Ensure it is oriented correctly (most are one‑way; the tapered side into the cover).

9. Install new hose and clamps
- Cut hose to length if needed. Push hose fully onto both fittings. Use worm clamps or OEM style clamps — tighten snugly but do not over‑torque and cut the hose. Ensure routing is smooth with no kinks and that it won’t chafe on hot parts.

10. Reassemble and start engine
- Reinstall any intake parts removed. Start engine and check for vacuum/leaks at the hose connections and around the grommet. Watch for oil leaks and listen for hissing.

How to test for blow‑by (crankcase pressure) — use a crankcase pressure gauge
1. Setup
- With engine warm and idling, remove oil filler cap or use an appropriate adapter in the oil filler neck to attach the crankcase pressure gauge/manometer. Some adapters thread into the PCV port — follow the tool instructions.

2. Measure
- At idle, normal crankcase pressure on healthy engines is generally neutral to a slight vacuum or small positive pressure depending on engine design (roughly −1 to 0 inHg vacuum to up to ~1 psi positive is typical). Sustained higher positive pressure (several psi) indicates excessive blow‑by (rings/cylinders/worn valves).

3. Interpret & follow up
- If pressure is high, you’ll need to investigate engine wear (compression/leakdown test) or clogged PCV/oil separator. If pressure is near normal after hose/PCV replacement, system is restored.

How to use the handheld vacuum pump to check PCV flow
- Disconnect the PCV hose at the intake side and attach the vacuum pump. With engine idling the pump should hold or show vacuum draw through the PCV when the engine is at idle and more vacuum when revved slightly. Absence of vacuum indicates blockage or stuck PCV.

Optional: clearing / flushing the blow‑by tube
- Only use low pressure compressed air; blow from the intake end toward the valve cover (opposite direction of normal flow) to push debris out. Do not force debris into the crankcase. Better option: replace the hose if heavily contaminated.

Common pitfalls & what to avoid
- Breaking brittle hoses or plastic fittings by excessive prying — twist and pull, use lubricant if needed.
- Forgetting to replace the grommet — leads to vacuum leaks and rough idle.
- Using the wrong diameter hose — causes leaks or premature failure; use high‑temp vacuum hose rated for oil/heat.
- Over‑tightening worm clamps and cutting into hose.
- Reinstalling hose with kinks or routing so it contacts hot exhaust components — it’ll fail fast.
- Ignoring a high crankcase pressure reading — replacing hoses only masks the symptom; high pressure usually means internal engine wear or clogged oil separator.
- Using high‑pressure air to clear hoses — can force sludge into the crankcase or damage seals. Use gentle air or replace hose.

Replacement parts typically required
- PCV valve (recommended)
- Breather/blow‑by hose (high‑temp/heat & oil resistant)
- Rubber grommet(s) for valve cover
- Small hose clamps or OEM clamps
- In some cases: valve cover gasket or valve cover if the boss is damaged

Quick tool usage notes (how to use the named tools)
- Hose‑clamp pliers: compress and slide off spring clamps; reuse only if in good condition.
- Pick set: remove old grommet and scrape light deposits—be careful not to gouge metal.
- Crankcase pressure gauge/manometer: plug adapter into oil filler or PCV port per tool instructions, start engine, read steady pressure at idle and under light throttle; compare to acceptable limits.
- Handheld vacuum pump: attach to PCV hose, apply vacuum and watch gauge to confirm one‑way flow and that the PCV draws vacuum with engine running.

That’s it — replace the hose, PCV valve, and grommet, check routing and clamps, then test crankcase pressure and PCV vacuum. If high blow‑by persists, perform compression/leakdown testing and inspect internal engine condition.
rteeqp73

Checking ECU codes on a 3rd gen Maxima (1989-1994) with VG30E engine. This shows how to check the ECU codes on a 3rd gen Maxima. It applies only to the VG30E engine (89-91 GXE+SE, and 92-94 ...

nissan hardbody VG30e burnout on dry bridge

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