christian louboutin black suede boots-Causes and diagnosis of engine idle speed instability

idle instability is encountered in most engine maintenance failures. If the idea of ​​an incorrect diagnosis will be extended repair time, reduced efficiency, even less so while waiting for the owner to another Automobile Factory. This paper is the practice of this failure in the long-term exploration and summary for the peer reference.

one, unstable idle classification

1. how to observe unstable idle

① observed jitter of the engine block, you can see the shaking of the oil dipstick level, smooth dipstick to clear, jitter dipstick to look double; ② tachometer from the engine block observation or reading paul smith suit, speed to idle expectations as the center of jitter, or jitter in the violent side of expectations, the program The standard idle idle expectations include the value of the load (Turn on the lights, hang gear automatic transmission, etc.) idle speed value, the value of idle air conditioning, warm-up idling value; ③ place to start the engine, sitting on the seat body feeling severe jitter.

2. by the law of classification

① appear cold (coolant temperature below 50 ℃) rhythmic instability; ② hot car (coolant temperature above 50 ℃) rhythmic instability; ③ erratic violent shake one or two.

3, according to the jitter levels in

① normal to idle expectations ± 10r/min jitter; ② general instability to idle expectations ± 20r/min jitter; ③ serious instability more than idle expectations ± 20r/min jitter; ④ side of expectations in idle shake violently.

4. by reason related categories

① direct cause of the mechanical parts means dirty, worn, incorrectly installed, leading to changes in individual cylinder power, resulting in the cylinder power is not balance, resulting in engine is idling instability; ② indirect causes, refers to the engine control system is not normal, resulting in poor combustion mixture, causing the cylinder power is difficult to balance the engine is idle instability.

5. by failure Taxonomy

① intake; ② fuel system; ③ ignition system; ④ engine mechanical systems.

6. idle shake mechanism

force changes in the gas cylinder (a cylinder gas cylinder gas force change or force a few changes), causing the cylinder power imbalance, resulting in the power stroke of the piston when the horizontal pitch is inconsistent, the emergence of horizontal roll down the engine torque imbalance, resulting in the engine shake. It can be said that any force causing changes in the gas cylinder engine failure can cause the engine idle shake.

two, unstable idle because

1. intake

(1) of the intake manifold or valve leakage

When should not enter the air, gasoline vapor, combustion exhaust gas into the intake manifold, resulting mixture is too thick or too thin, so that the combustion engine is not normal. When the leak location affects only the individual cylinder, the engine will be more severe jitter, a greater impact on the cold idle. Common reasons are: intake manifold hose clamp is loose or broken; intake manifold gasket leak; the intake manifold or other damaged parts will grind holes in the intake manifold; injector O-ring leak ; vacuum plug off radii shoes women, break; crankcase ventilation (PCV) valve opening degree; carbon canister valve is normally open; exhaust gas recirculation (EGR) valve closed lax and so on.

(2) fouling too much throttle and the inlet and around the inlet throttle

of coke, too much dirt, the air channel cross-sectional area changes, making can not precisely control idle speed control unit into the air, causing the mixture too thick or too thin, so burning is not normal. Common reasons are: throttle with oil or coke; throttle around the inlet with oil, coke; idle speed stepper motor, the duty cycle solenoid valves, rotary solenoid valve oil christian louboutin black suede boots, coke.

(3) idle air actuator failure

idle air actuator failure resulting in the idle air control is not accurate. Common reasons are: throttle motor damage or card; idle speed stepper motor, the duty cycle solenoid valves, rotary valve damage or card.

(4) inaccurate

into the gas control unit receives an error signal and sends the wrong order, causing gas into the engine idle speed control inaccurate, so that combustion is not normal, is not idle stability of the indirect causes. Common causes are: air flow meter or line failure; intake air pressure sensor or circuit failure; engine control unit plug or the result of bad water inside the computer failure.

2. Fuel System

(1) injector failure
injector fuel injection quantity uneven mist bad, causing the cylinder power is not given balance. Common reasons are: injector clogging, bad seal, spray the fuel into a linear and so on.

(2) the fuel pressure failure
low oil pressure, fuel spray from the injector or spray atomized fuel poor state into a linear, serious only emit droplets , fuel injection to reduce the mixture is too thin; oil pressure is too high, the actual fuel injection amount increases, so that the mixture is too thick. Common reasons are: fuel filter clogging; fuel pump filter clogged; fuel pump pumping capacity; fuel pump relief valve spring tension is too small; into the pipeline deformation; faulty fuel pressure regulator; return pipe flattened plug.

(3) the amount of fuel injection
inaccurate or line failure of the sensor, causing the control unit sends the wrong order, so that the fuel injection quantity is incorrect, resulting mixture is too thick or too thin, are idle the indirect causes of instability. Specific reasons are: air flow meter (or intake manifold pressure sensor) failure; throttle position sensor failure; throttle idle switch failure; coolant temperature sensor fault; the intake air temperature sensor failure; oxygen sensor failure; above the line sensor Circuit-breakers, short circuit, earth fault; engine control unit plug or bad because the water inside the computer failure.

3. ignition system

(1) ignition module and ignition coil
more recent years various models the ignition module and ignition coil made of one, ignition module or ignition Faulty coil mainly weak or high voltage spark ignition spark plug is not. Common reasons are: lack of ignition trigger signal; ignition module has failed; ignition module power or ground wire connection loose, bad; primary coil or secondary coil is faulty and so on.

(2) spark plugs and spark plug
high-voltage, high-voltage spark energy failure leading to decreased or fire. Common reasons are: spark plug gap is incorrect; spark plug electrode erosion or damage; spark plug electrode coke; magnetic spark plug insulator cracks; high-voltage resistance is too large; high-voltage insulated jacket or plug leakage; Distributor Rotor electrode erosion or poor insulation.

(3) the ignition timing is inaccurate
line fault is due to sensor and idle speed instability caused by indirect causes, the control unit sends the wrong order, so that the ignition timing is not correct, or cause the ignition advance angle large-scale fluctuations. Common causes are: air flow meter or the intake pressure signal failure; Hall sensor failure; coolant temperature sensor fault; the intake air temperature sensor failure; knock sensor fault; more sensor lines are open circuit, short circuit, earth fault; engine control unit due to bad water caused by plug or internal circuitry.

(4) other reasons
three yuan purification catalyst blockage caused by unstable idle, this failure at high speeds, the most easy to find. Automatic transmission, air conditioning, power steering is faulty idle speed will increase the load, cause idle instability. Engine control unit with air conditioning, automatic transmission control unit to enhance the signal interruption between the idle, the vehicle CAN-BUS installation of the bus system failure. With the new technology, new structure to increase, causing instability will be more idle, diagnosis must fully consider the issue.

4. mechanical

(1) Air Supply Valve
individual cylinder power failure led to decline too much, so that the cylinder power imbalance. Common reasons are: the timing belt installed in the wrong place, so that the cylinder valve opening and closing time of change, leading to inaccurate valve timing, the cylinder is not burning properly. Valve face and valve seat ring too much coke, Mifengbuyan valve, so that the cylinder compression pressure is inconsistent. Cam camshaft wear, the wear of the cylinder cam inconsistent leading to the inconsistencies in the amount of air entering the cylinder. Faulty valve related parts, such as putting wear and tear or bend the valve, rocker arm wear, stuck or leaking valve, valve spring break and so on.

I have encountered 2 cases due to a broken valve spring to intermittent idle shake, use a variety of detection equipment can not determine the cause, remove the valve springs after the discovery of the malfunction. In addition, the engine is equipped with hydraulic lifters, cylinder head, leading to installation of a trail of oil pressure relief valve when the pressure is higher than 300kPa, open the valve. If the valve is clogged, the pressure is too high because the hydraulic tappets stretch too much, leading to valve closed lax. There are a lot of coke back into the valve, so that the cold car just sprayed into the fuel adsorption, but can not enter the cylinder, the mixture is too thin cause cold fast idle instability.

(2) engine block, piston linkage
these failures will cause the individual cylinder power down too much, so that the cylinder power imbalance. Common reasons are: cylinder liner erosion or damage, resulting in single-cylinder leakage or leakage between the two cylinders; piston ring end gap is too large, corresponding or broken piston ring loses its elasticity; piston ring groove too much coke; piston and cylinder wear, cylinder roundness, cylindrical tolerance; after water caused by the cylinder rod bent to change the compression ratio; coke combustion chamber will change the compression ratio, coke serious cause idle instability.

(3) other reasons
crankshaft, flywheel, crankshaft pulley balancing rotating components such as failure, fracture damage the engine support pads, toe-boards for the engine oil pan with the deformation and impact, etc. these reasons will only lead to engine vibration without affecting speed.