Isuzu NPR NQR NPS NKR NHR N SERIES TRUCK Workshop Manual Digital Download

Tools & consumables
- 10, 12, 14 mm sockets + ratchet and extension; screwdriver set (flat, Phillips) and Torx/hex bits as required.
- Needle-nose pliers, pick set.
- Small nylon brush and soft-bristle toothbrush.
- Lint‑free shop rags, paper towels.
- Throttle-body cleaner (OE-compatible or dedicated TB cleaner; non‑chlorinated recommended). Do not use penetrating oil or heavy solvents on sensors.
- Spray straw for controlled bursts.
- Compressed air (optional) in short bursts.
- New throttle body-to-intake gasket or O‑ring(s).
- New intake boot clamp(s) or worm-drive clamps if original weak/corroded.
- Safety glasses, nitrile gloves, respirator if indoors.
- Multimeter and OBD2 scanner (for faults and relearn if required).
- Torque wrench (recommended for final bolts).
- Container for removed fasteners; magnetic tray.

Safety precautions
- Work in a well-ventilated area. Cleaner is flammable and fumes are hazardous.
- Wear eye protection and gloves.
- Disconnect battery negative terminal before removing throttle body or electrical connectors to avoid shorting sensors. Note: some vehicles require a throttle relearn/ECU reset after battery disconnect — see relearn notes below.
- Do not smoke or create sparks near cleaner.
- Keep rags, tools and loose hardware secure — do not drop into intake or engine.

Common pitfalls to avoid (summary)
- Spraying MAF, MAP, TPS, wiring harnesses or electrical connectors. Those can be damaged.
- Forcing the throttle plate on modern electronic throttle bodies (can damage plate shaft or motor).
- Using harsh solvents that corrode plastic or sensor coatings.
- Reinstalling with a damaged or missing gasket and causing vacuum leaks.
- Leaving rags inside the intake or throttle bore.
- Not performing throttle/idle relearn when required — results in high/low idle or check-engine lamp.

Step-by-step procedure (Isuzu N-Series throttle body cleaning)
Estimated time: 45–90 minutes (depending on access and required relearn).

1) Preparation
- Park truck on level ground, set parking brake, chock wheels.
- Ensure engine is cool (do not work on hot intake).
- Disconnect negative battery terminal. Wait 2–3 minutes to allow ECU to power down.
- Gather tools and replacement gasket/clamps.

2) Access and removal of intake duct
- Remove engine cover if present.
- Loosen clamps on air intake hose between airbox and throttle body. Use screwdriver or socket.
- Carefully pull off air intake duct. If rubber boot is stiff, work the clamp and slide off; avoid ripping boot.
- If equipped, unclip / unplug MAF sensor harness from airbox (do NOT spray MAF).
- Note hose routing, vacuum lines and sensor plugs. Label with tape if helpful.

3) Unplug throttle body electrical connectors & vacuum lines
- Unplug throttle position sensor/ETC connector(s) from the throttle body (press tab, pull straight out). Do not pull on wires.
- Disconnect any PCV/vacuum hoses attached to the throttle body. Inspect hoses for cracking — replace if brittle.

4) Remove throttle body (recommended for thorough cleaning)
- Remove bolts securing throttle body to intake manifold (usually 4 bolts). Keep bolts in tray.
- Carefully separate throttle body from intake manifold. The gasket may stick — remove it cleanly with a plastic scraper. Do not damage mating surfaces.
- Inspect gasket and replace with new one.

Notes if you choose to clean in‑place: you can clean without full removal but it increases risk of leaving residue, and makes thorough cleaning difficult. If in‑place, protect surrounding sensors and wiring with rags and tape.

5) Clean the throttle body
- Hold throttle body so the throttle plate faces up. Keep electrical connectors away from spray.
- Use short controlled bursts of throttle-body cleaner from ~20–30 cm (8–12 in). Let solvent loosen carbon for 10–30 seconds.
- Use a nylon brush to gently work carbon deposits from the bore, plate edge, and shaft area. Avoid metal scrapers that gouge the bore.
- If carbon is heavy at the plate edge and shaft, use targeted sprays and brush. For stubborn carbon, apply cleaner, wait 30–60 seconds, then agitate.
- Wipe residue with lint‑free rags until clean. Repeat spraying and wiping until no more black residue appears.
- Use compressed air short bursts to dry passages and remove loose debris (do not spin plate rapidly with air; short bursts only).
- Inspect the throttle plate pivot area for play or heavy wear — excessive play may indicate need for replacement.

How to use the tool (throttle body cleaner)
- Use the attached straw to direct short bursts. Do not soak the component — heavy wetting can contaminate sensors and actuators.
- Aim for edges and bore; avoid spraying wiring, connectors, or sensors.
- If the throttle body houses an electronic actuator or sensor assembly, do not spray the electrical/mechanical motor area directly; clean external carbon only and consider professional bench cleaning or replacement if internal contamination suspected.

6) Reassembly
- Ensure mating surfaces on intake manifold and throttle body are clean and dry.
- Install a new gasket or O‑ring. Do not reuse old gasket.
- Fit throttle body to manifold, start bolts by hand, then torque in a crisscross pattern to manufacturer spec. If spec unavailable, snug evenly (do not overtighten). Use torque wrench if you have spec (typical small throttle bolts often 8–12 Nm range — check workshop manual).
- Reconnect vacuum hoses, electrical connectors, and MAF connector if removed.
- Reinstall intake hose and clamps; use new clamps if old ones are weak. Ensure boot fits without twisting.
- Reconnect battery negative terminal.

7) Initial start & checks
- With vehicle in park/neutral and parking brake on, start engine.
- Observe idle and listen for vacuum leaks. If idle is erratic or high/low, allow engine to idle and stabilize.
- Check for stored trouble codes with OBD2 scanner. Clear codes if needed.

8) Throttle/idle relearn (general guidance)
- Some Isuzu N-series models with electronic throttle bodies require a relearn using either the scanner or the following general procedure:
- With A/C off, start engine and allow it to reach normal operating temperature.
- Let engine idle undisturbed for 5–10 minutes to allow ECM to recalibrate idle control.
- Cycle electrical loads (turn A/C on for ~10 sec, then off) and observe idle returning to normal.
- If idle remains unstable or CHECK ENGINE persists, perform an ECU relearn with an OEM-level scan tool or follow the exact procedure in the factory workshop manual for your model year.

9) Final inspection
- Inspect for vacuum leaks, loose clamps, or fuel odors.
- Road test and monitor engine performance. Re-scan for codes after test drive.

When to replace parts
- Replace throttle body assembly if:
- Electronic actuator or TPS is faulty (diagnosed with scanner or multimeter).
- Excessive shaft play or damaged bore/plate.
- Carbon impregnated into actuator body where cleaning won’t restore function.
- Always replace throttle body gasket/O‑rings after removal.
- Replace brittle or cracked intake boots and vacuum hoses.
- Replace clamps that no longer tighten securely.

Troubleshooting notes
- Persistent high/low idle after cleaning: check for vacuum leaks, faulty IAC (if equipped), TPS, or need for ECU relearn. Use OBD2 scanner for live data.
- Check engine lamp after cleaning: read codes — if throttle position sensor or throttle actuator codes present, investigate wiring and connectors before assuming part failure.
- If you shuffled the battery negative and now have limp mode or weird drivability, scan and perform relearn with a proper scan tool.

Final tips
- Use only throttle-body or carburetor cleaners labeled safe for modern fuel/air sensors.
- Work methodically; keep hardware organized and note hose routing.
- If unsure about electronic throttle motor/sensor handling, remove whole assembly and have a shop bench-clean or replace with a remanufactured assembly.

No questions asked.
rteeqp73

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