China Naming Network - Ziwei knowledge - Southeast Lingshuai Manual in 2007: Two Questions: 1. After driving for a while, the idle speed was unstable, upstream and downstream, and now it's almost 2300 rpm. What is the reason for not coming down?

Southeast Lingshuai Manual in 2007: Two Questions: 1. After driving for a while, the idle speed was unstable, upstream and downstream, and now it's almost 2300 rpm. What is the reason for not coming down?

It seems that the problem is quite troublesome. Unstable idle speed, up and down speed, black spark plug and black ash at the exhaust port all indicate that the fuel mixture is too rich and the combustion is not sufficient.

10 days have passed and there is not much oil left. What kind of engine has such a serious phenomenon of burning oil? Most of them are caused by the excessive clearance between the valve stem and the valve guide, and the damage, aging and falling off of the valve oil seal. We can check the condition of the oil seal by removing the valve cover, removing the camshaft again and pressing the valve spring with a special tool. At the same time, it can be judged whether a large amount of engine oil is wet by spark plugs.

In one case, serious cylinder pulling will also lead to such oil burning. Cylinder-pulling-mostly in the case of insufficient engine coolant, continue to drive, resulting in a sharp rise in engine temperature. Under the condition of insufficient heat dissipation, the cylinder liner, piston and piston ring have thermal expansion, which makes the fit gap of this friction pair smaller and produces dry friction. Once such a state occurs, firstly, the piston ring is not elastic enough to be sealed, so that the oil cannot be scraped off by the piston ring, and today it enters the combustion chamber to participate in combustion; When the piston expands when heated, it will deform, which may not be judged by glasses, but it is true. The deformed piston pulls the cylinder liner wall, that is, it pulls the cylinder, with longitudinal scratches. When the nail is scraped back and forth on the cylinder liner, traces can be felt, and the oil enters the combustion chamber from these pulled gaps.

It is difficult to judge the phenomenon of oil burning in cylinder pulling. There is a way to judge whether cylinder pulling is caused by a certain amount of disassembly work-use an electronic endoscope to enter from the installation hole of the spark plug, and carefully observe the side where the outer ring around the piston is combined with the cylinder liner to see if there is engine oil. If there is obvious wetting phenomenon, it is caused by cylinder pulling; If it is not obvious, it is not caused by cylinder pulling.

Excessive carbon deposition on the spark plug side electrode and the center electrode can also indicate that the carbon deposition is not very hard, but soft and black.

The cylinder and spark plug are dry carbon deposits, grayish brown and hard.

The water tank is boiling-perhaps because the engine temperature is too high. Perhaps not, but an illusion, the cylinder gasket burned through, and the compressed gas entered the cooling circulation system, causing the coolant to boil. The sealing condition of cylinder gasket can be detected by cylinder sealing test.

As for whether the engine needs overhaul or three guarantees, it depends on the engine. 1 Oil burning caused by valve oil seal. You can simply replace the valve oil seal and use special tools without removing the cylinder head. If the fit clearance between the valve guide and the valve stem is too large, it is necessary to remove the cylinder head and replace it-if the oil seal, guide and valve fail, they should also be replaced. If it is a cylinder part problem, please check the condition of the cylinder liner while disassembling the cylinder head. 1-There is no strain in the whole stroke of the cylinder liner, or the strain is not obvious. The cylinder liner can be manually polished with fine sandpaper 1200-simply polished. If this work is completed, which piston and piston ring must be replaced.