Short summary: the throttle body (throttle valve / intake control valve) meters air into the engine. On the Toyota 1DZ‑II (industrial diesel) it can gather carbon and soot from EGR and crankcase blow‑by; that buildup makes the plate stick or lets the valve not seal, causing rough idle, stalling, poor response and emissions codes. Cleaning restores smooth airflow and consistent idle. Below is a beginner‑friendly, step‑by‑step guide that names and explains every important component, gives the theory, lists failure modes, and shows how to clean safely and correctly.

What the system is and why cleaning is needed (theory, analogies)
- Purpose: The throttle body is a valve in the intake tract that controls airflow into the intake manifold. In many diesels (including typical forklift/industrial Toyota diesels) a throttle or intake control valve is used for idle control, emissions (EGR control), and some transient control — it’s not the same as a gasoline “drive/accelerator” throttle but it performs a similar flow‑metering function.
- How it works (simple): Think of the throttle like a door in a hallway leading to a room (the engine). The door (throttle plate) rotates on a shaft to open and close the hallway. Sensors (throttle position sensor or TPS) tell the engine computer how much the door is open. An idle air control device or servo may slightly open the door when needed. EGR soot and blow‑by sludge land on the plate and the nearby bore; over time the “door” sticks or cannot fully close.
- Why carbon builds: Exhaust gas recirculation (EGR) routes soot back into the intake, and crankcase ventilation sends oily vapors. Those vapors and soot stick to the throttle plate and bore, creating a gummy, carbon ring that prevents smooth movement and sealing.
- Effects of a dirty throttle: rough/unstable idle, stalling, higher fuel use, poor throttle response, smoke, reduced low‑end torque, and engine codes (e.g., idle control, throttle position discrepancies).
- Analogy: imagine breathing through a pipe whose flap is sticky. You can still breathe but it’s hard to control how much air gets through, so you cough, gasp, and can’t steady your breath — cleaning the flap fixes the problem.

Components you will encounter (every important component, described)
- Air cleaner / intake hose: big rubber/plastic hose connecting air box to throttle body. Has clamps (worm gear or spring).
- Intake duct flange and clamps: hold and seal the hose to the throttle body.
- Throttle body assembly (aka intake control valve): main metal housing with a cylindrical bore and a pivoting throttle plate inside.
- Throttle plate (butterfly): the flat disc that rotates to open/close the bore.
- Throttle shaft: the rod the plate is mounted on — pivots inside bushings or bearings.
- Mounting flange and bolts: bolts that attach the throttle body to intake manifold.
- Gasket or O‑ring: seals between throttle body and intake manifold.
- Throttle position sensor (TPS): electrical sensor bolted to the throttle body shaft that reports plate angle to the ECU.
- Idle control actuator or stepper/solenoid (if present): device that allows fine idle air adjustment.
- Wiring harness and electrical connectors: connect TPS and actuator to the ECU.
- Vacuum lines (if present): small hoses for vacuum switching valves or EGR control attached near the throttle body.
- EGR valve and passages (nearby): sources of soot; don’t forget they feed the intake.
- Fasteners and linkages: bolts, nuts, and any mechanical linkage if present.
- PCV/crankcase ventilation hose: may be attached nearby and carry oily vapors.

Tools and materials
- Tools: basic socket set (metric), ratchet, extension, screwdrivers (flat & Phillips), Torx/Allen if required, pliers, small pick, shop rag, soft brass or nylon brush, torque wrench (recommended), container for bolts, small flashlight.
- Materials: throttle body / intake cleaner (non‑chlorinated or explicitly labeled safe for throttle bodies), clean lint‑free rags, nitrile gloves, safety glasses, gasket if replacing (recommended), carburetor/parts brush, paper towels.
- Optional: small vacuum pump or compressed air for blow out; masking tape to mark position; service manual for torque specs and throttle relearn procedure.

Safety and preparatory steps
- Work in a well‑ventilated area. Throttle cleaner is flammable and emits fumes.
- Wear gloves and eye protection.
- Disconnect the negative battery terminal to prevent accidental actuator movement or shorting electrical connectors. Wait 1–2 minutes for capacitors to discharge (some systems need that).
- Let the engine be cool to avoid burns.

Step‑by‑step cleaning procedure (beginner friendly)
1) Note and mark before you disconnect
- With the intake hose clamped on, note the orientation of the throttle body and mark the relative position of wire connectors and bolts with tape or a marker. This makes reassembly easier.
- If there are vacuum lines, note or photograph routing.

2) Disconnect battery negative terminal
- Prevents accidental electrical activation and clears some adaptive memory.

3) Remove intake hose and air cleaner duct
- Loosen the hose clamps (worm drive or spring clamps) and gently twist‑pull the hose off the throttle body flange. Inspect hose for cracks — replace if damaged.
- Unclip or remove air box as needed to access the throttle body.

4) Unplug electrical connectors and vacuum lines carefully
- Depress locking tabs and pull connectors straight off. Don’t yank wires.
- Use small pliers to remove vacuum hoses; tag them if multiple.

5) Inspect throttle body in place
- With connectors off and air hose removed, manually open the throttle (use the linkage or rotate the shaft gently) and look for carbon deposits on plate edges and bore.

6) Decide whether to clean in‑place or remove
- Light deposits: you can clean in place by spraying cleaner on a rag and wiping the plate and bore while actuating the plate.
- Heavy deposits or the need to replace gasket: remove the throttle body from the intake manifold. To remove, unbolt the mounting bolts in a crisscross pattern and lift the throttle body straight out.

7) Remove throttle body (if removing)
- Keep bolts in order. Old gaskets should be scraped off carefully and surfaces cleaned with a plastic scraper—don’t gouge mating surfaces.
- Inspect throttle shaft for play: grab the plate and wiggle. Excessive looseness or scoring of the bore or shaft means wear — replacement may be required.

8) Cleaning the throttle body
- Use throttle body / intake cleaner. Avoid using harsh chlorinated solvents on sensors or painted parts.
- If the TPS or any electrical component is removable, cover it or remove it according to manual. Do not soak TPS electronics.
- Apply cleaner to the carboned areas. Let soak for a minute, then use a soft nylon or brass brush to scrub the plate and bore where carbon has accumulated. Wipe away loosened carbon with a clean lint‑free rag.
- Manually rotate the plate to get the edge and the full circumference of the bore. Clean both sides of the plate.
- For heavy EGR soot, repeat spray/soak/brush cycles until clean. Use compressed air to blow dry and to clear passages (blow away from yourself).
- If there’s an idle actuator, clean its external housing and ports; do not disassemble unless you have the manual.
- Do not let large amounts of cleaner run into the intake manifold—use rags to block off openings if necessary.

9) Inspect seals, shaft and sensors
- Check the throttle shaft for pitting, scoring, or excessive side‑play. Check the gasket — replace if compressed or brittle.
- Inspect wiring connectors and pins; clean lightly with electrical contact cleaner if corroded.

10) Reassembly
- Install a new gasket (recommended) and place throttle body onto manifold. Tighten the mounting bolts evenly in a crisscross pattern.
- Torque: use the service manual torque specs. If you don’t have the manual, small throttle body bolts typically are 6–12 Nm (4–9 ft‑lb) — tighten snugly and evenly; do not over‑torque.
- Reattach vacuum hoses, wiring connectors, air intake hose, and clamp. Reconnect battery negative.

11) Initial startup and relearn
- Some ECUs will relearn idle automatically. Start the engine and let it idle. It may idle high initially as the ECU re‑learns. Allow to reach normal operating temperature.
- Cycle the throttle manually a few times (blip) and let it return to idle to help the computer adapt.
- If the vehicle has a formal throttle relearn procedure (service manual), follow it (sometimes key on/off cycles, specific idle rpm for a time, or using diagnostic tool).
- Check for leaks, listen for irregular idle, and scan for stored diagnostic trouble codes (DTCs); clear codes if appropriate and see if they return.

12) Final checks
- Recheck clamps and bolts after a short test drive or running the engine a few minutes.
- Verify idle is stable and throttle response is better. Monitor for any new warning lights.

What can go wrong (failure modes and mistakes to avoid)
- Damaging the TPS or electrical connectors: do not spray cleaner directly into connectors; don’t force connectors off; don’t rotate the shaft with TPS disconnected excessively (some TPS has physical limits).
- Breaking throttle shaft or bearings: aggressively prying on the plate or forcing the shaft can damage bushings. If shaft is seized, apply penetrating oil to the bolt only and use correct tools; if stuck, better to remove the whole unit and soak.
- Creating vacuum leaks: using the wrong gasket, not seating it properly, or overtightening bolts (distorting flange) can cause intake leaks and worse idle issues.
- Pushing cleaner into the intake manifold: excessive cleaner down the intake can foul sensors or contaminate oil pans (on some engine layouts) — use rags to limit fluid flow and spray sparingly.
- Improper torque: under‑torque can leak; over‑torque can strip threads or warp the throttle body.
- Not replacing damaged gaskets or hoses: a cracked intake hose will negate cleaning by letting unmetered air in.
- Not checking for deeper causes: heavy soot may indicate a malfunctioning EGR system, PCV, or turbo seals. If the throttle gets dirty again quickly, inspect EGR, PCV and intake for deeper faults.
- Damaging the idle actuator by disassembly: don’t disassemble electromechanical idle actuators without the manual.
- Not following relearn procedure: may leave idle unstable or throw codes.

When to replace instead of clean
- Excessive shaft play or scored bore that allows unmetered air past the plate.
- TPS or idle actuator failure (diagnostic codes or nonfunctional).
- Severe corrosion or damage to mounting flange or mating surfaces.
- If cleaning fails to restore proper idle or the soot comes back very quickly (indicates underlying issue).

Maintenance frequency and tips
- For engines with heavy EGR and use in dusty/stop‑and‑go environments (forklifts, material handling), check throttle body every 6–12 months.
- Keep intake hoses and clamps tight; change PCV elements and air filters on schedule to reduce contamination.
- If you find heavy soot, inspect and service the EGR valve and PCV system too.

Quick troubleshooting checklist (if problems continue after cleaning)
- Check for vacuum leaks (spray soapy water off‑engine or use propane around gasket with engine running — observe idle change).
- Scan ECU for DTCs; inspect TPS voltage with a multimeter (smooth change across throttle sweep).
- Inspect EGR for excessive operation or stuck open.
- Check intake hose, air filter, and PCV hoses for cracks and blockages.
- Measure throttle shaft play; replace throttle body if out of spec.

Final practical notes
- Use the correct cleaner (throttle/intake cleaner). Some carb cleaners are too harsh for modern sensors.
- Keep a clean work area and organize bolts so nothing is left out.
- If you’re unsure about torque values or a relearn procedure, refer to the Toyota service manual for the 1DZ‑II or a dealer manual for exact specs and ECU procedures.

That’s it — follow the steps carefully, keep parts and connectors clean, and replace gaskets. Cleaning typically takes 45–90 minutes depending on access and how dirty the unit is.
rteeqp73

TOYOTA 1DZ 1DZ-II, 1DZ-2 ENGINE FORKLIFT AIRPORT SHUTTLE BUS MOTORES @user-gz8ni9pe7v WHATSAPP/WECHAT: +86-185- 7643- 6547 EMAIL: TWOOAUTO @HOTMAIL.COM SKYPE: AUTOPARTSOO WEBSITE: ...

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