◆◆发动机加速不良◆◆
电喷发动机加速不良的主要原因有以下几点:
1. 节气门位置传感器故障。节气门位置传感器以输出电压变化率信号来反映加速的快慢。当节气门位置传感器出现故障或调整不当时,电脑接收不到正确的加速信号,也就无法调整喷油量及点火时刻,造成发动机加速无力。
2. 燃油系统压力过低。当电动燃油泵、油压调节器等有故障造成油路油压过低时,虽然电脑给加速和加浓信号,但由于喷油压力过低,使发动机得不到加速时需要的喷油量,造成发动机加速无力。
3. 点火时间过迟或过早。当点火时刻过迟或过早时,由于点火系统不能给出加速时的准确的点火时刻,造成发动机加速不良。
4. 火花塞工作不良。主要是花火塞间隙过大过小,火弱、淹死、击穿、积炭、断火、不跳火。
5. 空气流量计(进气管压力传感器)故障或真空管路漏气。当空气流量计(进气管压力传感器)出故障或真空管路漏气时,就不能向电脑提供正确的空气量信号,电脑也就不能输出正确的喷油脉冲信号,从而使发动机加速无力。
6. 喷油器工作不良。
电喷发动机加速不良的检查流程图 ▼
【故障实例1】
故障现象:使用中,轿车行驶无力,发动机加速不良,怠速时运转不平稳,急加速时进气管有回火现象。
故障原因:混合气过稀,电喷系统对空燃比失控。迈腾轿车采用热线式空气流量计,热线由金属铂丝制成,伸入到节气门体的旁通气道中。因气流的冷却作用而使电阻值发生变化。加大流过热线的电流,使热线电阻值随温度升高而升高。在调节过程中,空气流量计传给ECM的电压信号随空气流量的变化而变化。使用低质燃油,进气管产生回火,使过多的杂质和积炭胶结在金属铂丝上,当空气流量计的热线被沾污后,污物影响热辐射,使冷却效应降低。传给ECM的电压信号便会偏低,造成混合气过稀。
故障排除:拆下空气流量计,用化油器清洗剂喷洗,除掉热线上的污垢,使空气流量计正常工作。更换不合格的燃油,发动机工作正常。
【故障实例2】
车型:奥迪A6轿车故障现象:发动机急加速不良,有回火现象,缓加速正常故障原因:混合气过稀,空燃比失控故障排除:使用VAG1552进行发动机故障查询,空气流量传感器、节气门开度、冷却液温度传感器、进气温度传感器的信号数值均在规定范围内。对各执行器元件进行测试也都正常。检查点火正时和配气相位及气缸压力,均正常。检查前保险杆后的进气管压力传感器,连接松动,拧紧松动处故障排除
◆◆电喷发动机转速忽高忽低◆◆
可能的故障原因:① 燃油泵工作不良,使油路油压过低。② 真空管泄漏。③ 汽油中有杂质,使主喷油器的喷油量不稳定。④ 温度传感器、温控开关、电脑(ECU)等工作失常,使冷启动喷油器误动作。⑤ 废气再循环(EGR)阀工作不正常,或控制失常。电喷发动机转速忽高忽低的检查流程 ▼
◆◆怠速不稳容易熄火◆◆
1. 氧传感器工作不良或损坏发动机每次工作循环的喷油量由装在排气管中的氧传感器反馈给电脑,电脑根据此反馈信号修正喷油量,达到燃烧最完全的目的。氧传感器正常输出电压信号在0.2~0.9V之间变化,在节气门打开过程中,如果其电压信号无变化,说明氧传感器损坏。使用含铅汽油,会使氧传感器“中毒”失效。由于氧传感器失效,电脑得不到氧传感器的反馈信号,也就无法修正喷油量,使怠速时供给发动机过浓或过稀的混合气,造成发动机怠速工作不稳。
2. 点火过早或过迟当点火过早或过迟时,由于不能准时点燃混合气也会造成怠速工作不急。3. 火花塞损坏、高压线路漏电或断路当火花塞损坏,高压线路漏电、断路,都会造成发动机缺缸工作,使其怠速不稳。4. 排气再循环(EGR)系统工作不良现代轿车有些安装有EGR系统,EGR系统工作时,将一部分废气再引进气缸中,降低气缸中的燃烧温度,以达到降低NOx的排放目的。正常情况下,在怠速时EGR阀处于关闭状态,并不进行废气再循环。当EGR阀积炭或其他原因,造成EGR阀在怠速时关闭不严,致使在怠速时仍有废气进入气缸中,造成怠速工作不稳。5. 喷油器故障当喷油器损坏、堵塞或其控制线路有故障时,也会造成发动机怠速不稳。6. 电脑线路故障若电脑线路接头松动或接触不良,也会造成发动机怠速时断油或断火,使发动机工作不稳,怠速发抖。
◆◆电喷发动机燃油消耗过大◆◆
1. 进气管压力传感器损坏或其上的真空管路漏气。电控燃油喷射的喷油量由进气管压力传感器、发动机转速、水温传感器、节气门位置传感器等信号组成,主要提供供油信号。
当进气管压力传感器损坏或其上真空管脱落时,电脑便判断发动机处于大负荷状态,做出加浓喷油处理,使混合气过浓,燃油消耗过多。
2. 燃油压力调节器不良或其上真空管脱落。当燃油压力调节器不良或其上真空管脱落时,造成燃油压力过高,从而使燃油喷射过多。
3. 水温传感器不良或其线路断路。当水温传感器不良或其上线路断路时,电脑判断发动机处于冷状态下工作,提供过浓的混合气,燃油消耗增加。
4. 电脑不良或其线路有故障。
5. 燃油蒸气净化罐和气阀工作不良。
原创文章,作者:cesifu,如若转载,请注明出处:http://www.cesifu.com/article/63348.html
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