s10 service manual
Post on 03-Oct-2014
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TESTING1. Remove the PCV valve from the rocker arm cover, but leave the vacuum hose attached. 2. Operate the engine at idle speed. 3. Place your thumb over the end of the valve to check for vacuum. If no vacuum exists, check the valve, the hoses or the manifold port for a plugged condition. Fig. 1: To test for vacuum, remove the PCV valve from the grommet, with the hose attached
4. Remove the valve from the hose(s), then shake it and listen for a rattling of the check needle (inside the valve); the rattle means the valve is working. If no rattle is heard the valve is stuck, and should be replaced.
REMOVAL & INSTALLATIONPCV Valve The large end of the valve is inserted into a rubber grommet in the valve cover. At the narrow end, it is inserted into a hose and usually clamped. To remove it, gently pull it out of the valve cover, then open the clamp with a pair of pliers. Hold the clamp open while sliding it an inch or two down the hose (away from the valve), and then remove the valve. If the end of the hose is hard or cracked where it holds the valve, it may be feasible to cut the end off if there is plenty of extra hose. Otherwise, replace the hose. Replace the grommet in the valve cover if it is cracked or hard. Replace the clamp if it is broken or weak. In replacing the valve, make sure it is fully inserted in the hose, that the clamp is moved over the ridge on the valve so that the valve will not slip out of the hose, and that the valve is fully inserted into the grommet in the valve cover.
PCV Breather Most breathers are located inside the air cleaner assembly, though they may be mounted directly to a valve cover. Although a breather may in some cases be removed and cleaned, it is an inexpensive part and it is wise to replace it if dirty. Breathers which are mounted directly to the valve cover may be simply grasped and pulled from the cover grommet. For breathers which are mounted inside the air cleaner follow the procedure listed below. 1. Loosen the wing nut or release the retainers, then remove the top of the air cleaner assembly. 2. Slide the rubber coupling that joins the tube coming from the valve cover to the breather off the breather nipple. 3. Slide the spring clamp off the breather nipple (if equipped) which is protruding from the air cleaner housing, then withdraw the breather from inside the air cleaner assembly. 4. Inspect the rubber grommet in the valve cover and the rubber coupling for brittleness or cracking. Replace parts as necessary. 5. Installation is the reverse of removal.
Evaporative Emission Control System (EECS)
OPERATIONThe Evaporative Emission Control System (EECS) is designed to prevent fuel tank vapors from being emitted into the atmosphere. Gasoline vapors are absorbed and stored by a fuel vapor charcoal canister. The charcoal canister absorbs the gasoline vapors and stores them until certain engine conditions are met, then the vapors are purged and burned in the combustion process. The charcoal canister purge cycle is normally controlled either by a thermostatic vacuum switch or by a timed vacuum source, though a few later model vehicles may use electronic regulation in the form of a purge control solenoid. The thermostatic vacuum switch is installed in a coolant passage and prevents canister purge when engine operating temperature is below approximately 115F (46C). A timed vacuum source uses a manifold vacuum-controlled diaphragm to control canister purge. When the engine is running, full manifold vacuum is applied to the top tube of the purge valve which lifts the valve diaphragm and opens the valve. If equipped with a purge solenoid, under proper engine operating conditions the ECM will signal the solenoid which will then open the vacuum line allowing manifold vacuum to control the purge diaphragm. Most solenoids used on these vehicles are normally closed and will open when the ECM provides a ground signal energizing the solenoid. NOTE: Remember that the fuel tank filler cap is an integral part of the system in that it is designed to seal in fuel vapors. If it is lost or damaged, make sure the replacement is of the correct size and fit so a proper seal can be obtained. A vent, located in the fuel tank, allows fuel vapors to flow to the charcoal canister. A tank pressure control valve, used on high altitude applications, prevents canister purge when the
engine is not running. The fuel tank cap does not normally vent to the atmosphere but is designed to provide both vacuum and pressure relief. Poor engine idle, stalling and poor driveability can be caused by a damaged canister or split, damaged or improperly connected hoses. Evidence of fuel loss or fuel vapor odour can be caused by a liquid fuel leak; a cracked or damaged vapor canister; disconnected, misrouted, kinked or damaged vapor pipe or canister hoses; a damaged air cleaner or improperly seated air cleaner gasket.
TESTINGCharcoal Canister and Purge Valve The fuel vapor canister is used to absorb and store fuel vapors from the fuel tank. Vacuum sources are generally ported, either through an internal or remote mounted purge control valve. Engines employing the timed vacuum source purge system usually use a canister purge valve which is integral to the vapor canister. The valve consists of a housing and tube moulded into the canister cover, valve assembly, diaphragm and valve spring. The diaphragm cover has a built-in control vacuum signal tube. 1. Remove the vacuum hose from the lower tube of the purge valve and install a short length of tube, then try to blow through it (little or no air should pass, though a small amount may pass if the vehicles is equipped with a constant purge hole). 2. Using a vacuum source such as a hand vacuum pump, apply 15 in. Hg to the upper tube of the purge valve. The diaphragm should hold the vacuum for at least 20 seconds, if not replace the purge valve (remote mounted) or canister (internal mounted valve), as applicable. 3. While holding the vacuum on the upper tube, blow through the lower tube (an increased volume of air should now pass); if not, replace the valve or canister, as necessary.
Fig. 1: Common EEC system schematic 2.5L and 4.3L (VIN Z, except Turbo) engines shown
5. NOTE: When testing valves by blowing air through them, be careful that you are blowing in the proper direction of flow. Many valves are designed to only allow air to flow in one direction and a proper working valve may seem defective if it is tested with air flow only in the wrong direction. Thermostatic Vacuum Switch (TVS) NOTE: The number stamped on the base of the switch (valve) is the calibration temperature. 1. With engine temperature below 100F (38C), apply vacuum to the manifold side of the switch. The switch should hold vacuum. 2. As the engine temperature increases above 122F (50C), vacuum should drop off. 3. Replace the switch if it fails either test. NOTE: A leakage of up to 2 in. Hg/2 min. is allowable and does not mean that the valve is defective. Canister Purge Control Solenoid As stated earlier, most solenoids found on these vehicles use a normally closed solenoid valve. This means that when the solenoid is de-energized it is closed or, when it is energized it will open allowing vacuum to pass. On most vehicles equipped with this solenoid, fused ignition voltage is applied to the solenoid through one of it's terminals. When the ECM recognizes proper engine operating conditions, it will provide a ground through the other solenoid terminal in order to energize the solenoid.
To test a normally closed solenoid valve, try blowing air through the valve fittings when the engine is OFF, air should not flow. When the engine is running the solenoid should de-energize during engine warm-up and energize once it has reached normal operating temperature and proper running conditions.
REMOVAL & INSTALLATIONCharcoal Canister 1. Tag and disconnect them from the canister assembly. NOTE: If access to the vapor hoses is difficult with the canister installed, wait until the canister is released from the bracket or mounting, then reposition the canister for better access. 2. Loosen the screw(s) fastening the canister retaining bracket to the vehicle. 3. Carefully remove the canister or canister and bracket assembly, as applicable. 4. Installation is the reverse of removal. Thermostatic Vacuum Switch (TVS) The TVS is located near the engine coolant outlet housing. 1. Drain the engine cooling system to a level below the TVS. 2. Disconnect the vacuum hose manifold from the TVS. If the hoses are not connected to a single manifold, be sure to tag them before removal to assure proper installation. 3. Using a wrench, unthread and remove the TVS from the engine. To install: 4. Apply a soft setting sealant to the TVS threads. NOTE: DO NOT apply sealant to the sensor end of the TVS. 5. Install the TVS and tighten to 120 inch lbs. (13 Nm). 6. Reconnect the vacuum hoses. 7. Properly refill the engine cooling system, then run the engine and check for leaks.
Fig. 1: Disconnect the vacuum hoses from the TVS
Fig. 2: Loosen and remove the thermostatic vacuum switch using a wrench
Exhaust Gas Recirculation (EGR) System
OPERATIONThe EGR system is used to reduce oxides of nitrogen (NOx) emission levels caused by high combustion chamber temperatures. This is accomplished by the use of an EGR valve which opens, under specific engine operating conditions, to admit a small amount of exhaust gas into the intake manifold, below the throttle plate. The exhaust gas mixes with the incoming air
charge and displaces a portion of the oxygen in the air/fuel mixture entering the combustion chamber. The exhaust gas does not support combustion of the air/fuel mixture but it takes up volume, the net effect of which is to lower the temperature of the combustion process. The EGR valve is usually mounted on the intake man