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Massive Star Formation:Observations confront Theory ASP Conference Series,Vol.xxx,2008H.Beuther et al.Recent Astrochemical Results on Star-Forming Regions Floris van der Tak SRON Netherlands Institute for Space Research Landleven 12,9747AD Groningen,The Netherlands;vdtak@sron.nl Abstract.This review discusses recent results on the astrochemistry of (mostly high-mass)star-forming regions.After an introduction on the use of chemistry in astrophysics and some basic concepts of astrochemistry,speci?c re-sults are presented.Highlighted areas are the use of chemistry in the search for massive circumstellar disks,the interaction of molecular clouds with cosmic rays,and the feedback e?ects of protostellar irradiation on the parent molecular cloud.The review concludes with a discussion of future observational opportunities.1.The use of chemistry in astrophysics There are several ways in which knowledge of chemistry is helpful to gain a better understanding of the Universe.The prime area of interest is the formation of stars and planets,which occurs in cold dark clouds which require observation at long (infrared and radio)wavelengths.The line radiation of molecules is an essential part of this e?ort,because it is the only probe of the kinematics of these clouds,and because it is the major way to determine their temperatures,volume densities,and other conditions.Successful use of molecular lines to derive physical parameters requires some understanding of chemistry to predict which molecules may be abundant under which conditions.This use may be called ‘passive’astrochemistry.A more active way to use chemistry in astrophysics makes use of the depen-dence of the molecular composition of the gas on parameters which are otherwise hard to estimate.This use involves the construction of chemical models typically containing thousands of reactions;Wakelam et al.(2006a)have studied the ac-curacy of such models.First,the chemical composition of the gas in such models
usually depends on the time,so that observations of molecular lines may be used to estimate the ages of star-forming regions (Doty et al.2006).Second,since the chemistry needs time to respond to changing conditions,molecular abun-dances often contain some memory of the source history.An example are the deuterium bearing molecules seen in hot molecular cores,which must be rem-nants of a previous cold phase.Third,the chemical composition of star-forming matter may give clues to the presence of (energetic)radiation which is di?cult or impossible to observe directly.It is clear that chemistry is a signi?cant help in the understanding of astrophysical processes.
More than 130molecules are known to exist in interstellar space,of which 36are known outside our Galaxy and 10are known in the solid state (Gibb et al.2004).The eight new discoveries of 2007(see www.cdms.de for the latest up-dates)may be grouped in a few ‘threads’:(i)Complex organics (by which
1
2Floris van der Tak
astronomers usually mean4+-atomic carbon chains),which probe gas-grain in-teractions and serve as a link to pre-biotic molecules;the most recent addition is C3H6(Marcelino et al.2007).(ii)Fluorine and phosphorus compounds(PO, HCP,CF+),which help to determine elemental abundances and the composi-tion of dust grains in dense clouds(Neufeld et al.2006;Ag′u ndez et al.2007; Tenenbaum et al.2007).(iii)Negative ions,which are useful to measure the electron fraction of molecular gas(§4.).(iv)Deuterated molecules,which are important as tracers of very early(cold and dense)phases of star formation (§3.).
Due to space limitations,this review is not comprehensive,but biased to-ward the interests of its author.For a recent general review of astrochemistry see the books edited by Lis et al.(2005)and Combes(2007).The physics and chemistry of regions of low-mass star formation are reviewed by Bergin&Tafalla (2007)and Ceccarelli et al.(2007).An overview of methods to derive molecular abundances from spectral line data can be found in Van der Tak&Hogerheijde (2007).The formation of high-mass stars is reviewed by Zinnecker&Yorke (2007)and Beuther et al.(2007),and is of course the topic of the current vol-ume.
2.Basics of Astrochemistry
The chemical composition of interstellar molecular clouds depends strongly on the physical conditions,particularly the temperature and the radiation?eld. This discussion is restricted to dense interstellar clouds,de?ned theoretically as n>～104cm?3or observationally as A V>～3,so that photoprocesses can be ignored. In such clouds,four main types of environments can be distinguished:
Cold gas At T<～100K,the main type of reactions occurring in the gas phase are ion-molecule reactions.An example is the proton transfer from H2to CO:CO+H+3→HCO++H2.This type of reaction usually does not have any activation barrier and usually proceeds at about the‘Langevin’rate of ～10?9cm?3s?1.The necessary ions are produced in the interaction of H2 with cosmic rays(§4.).One major source of uncertainty are the rates and the branching ratios of dissociative recombination reactions of ions with free electrons(Florescu-Mitchell&Mitchell2006).
Warm gas Reactions between two neutral species occur if the gas is warm enough to overcome their activation barriers.The rates of these reactions and the heights of their barriers can be di?cult to measure or predict,especially when radicals are involved.A classic case is the reaction O+OH→O2+H with a measured rate constant of3.5×10?11cm?3s?1at T=40K,well above the predicted value(Xu et al.2007).This reaction determines the main oxygen reservoir in cold interstellar clouds,which is di?cult to measure because the?ne structure lines of O0do not probe cold gas and O2only has weak quadrupole lines.The abundance of O2recently measured with the Odin satellite towards theρOph cloud(Larsson et al.2007)is well below theoretical https://www.doczj.com/doc/8d15535439.html,b-oratory data at T<40K and observations with Herschel(§6.)are needed for further progress.
Chemistry of star-forming regions3 Cold dust In dense clouds,the surfaces of dust grains act as catalysts for reactions that would not take place in the cold gas phase.An important exam-ple is the formation of H2CO and CH3OH by successive additions of H atoms to CO molecules.Recent laboratory experiments indicate that this process is very e?cient(Watanabe et al.2004;Fuchs et al.2007).One uncertainty in modeling such processes is the roughness of the surface which determines the mobility of the H and O atoms(e.g.,Cuppen&Herbst2005).Depending on this parameter,grain surface chemistry may operate at temperatures up to～100K (Cazaux et al.2005),but this remains subject of discussion(Herbst et al.2005). Warm dust When dust grains are heated by the radiation from young stars or by interstellar shock waves,any ice layers will evaporate.The evaporation temperature varies from≈20K for volatile species such as CO and N2to≈110K for the more refractive H2O molecule which makes up the bulk of the ice mantle (Collings&McCoustra2005).
Observations of dense molecular cores without embedded stars often show a di?erentiation between CO and N2:in the core centers,CO appears depleted while N2(traced by N2H+and NH3)remains in the gas phase(e.g.,Tafalla et al. 2002).This behaviour cannot be due to the di?erence in evaporation tempera-ture between the two species which Bisschop et al.(2006)has shown to be very small.Alternatively,CO freeze-out removes the major destroyer of N2H+,so that its abundance rises toward the centers of pre-stellar cores(Aikawa2007), but this e?ect does not quite explain the observations(Flower et al.2006).
Signi?cant rearrangement of the ice layers may occur during the warm-up phase of the ice before the actual evaporation,which may lead to the formation of more complex molecules(Garrod&Herbst2006).This rearrangement is a more likely source of molecular complexity than gas-phase processes,the preferred model of the1990’s.
3.Chemical Filters
The rate coe?cients of many chemical reactions depend on the temperature.If the dependence is very strong,a molecule may almost exclusively exist in warm or cold gas.In an astrophysical context,this behaviour may be used to trace regions of a particular temperature,a concept known as a chemical?lter.Three particular cases are:
Cold gas:H2D+The H2D+molecule is produced in the gas phase by the reaction of H+3with HD.At T<～20K,the back reaction is very slow,and if in addition the density is high(>～105cm?3),the main destroyers of H2D+,CO and O,will freeze out onto dust grains.Under these circumstances,the H2D+/H+3 ratio may approach or even exceed unity,and further reaction to D2H+and D+3may even occur(Roberts et al.2003).High abundances of H2D+measured in a few dense pre-stellar cores and of D2H+in one con?rm these predictions (Caselli et al.2003;Belloche et al.2006;Hogerheijde et al.2006;Vastel et al. 2004).A survey of H2D+in12dense molecular cores with and without embed-ded stars clearly shows a decrease of the H2D+abundance as the young star
4Floris van der Tak
warms up its surroundings(Caselli et al.2007).The H2D+molecule thus acts as a?lter for the cold dense gas at the centers of pre-stellar cores where most other molecules are frozen onto dust,and is the only probe of the kinematics in this phase(e.g.,Van der Tak et al.2005).
Regions of high-mass star formation tend to have lower degrees of deuterium fractionation than their low-mass counterparts;see Fontani et al.(2006)for a recent example.The implication is that the cold pre-stellar phase for regions of massive star formation has a short duration compared with the low-mass case, or that the ambient gas is warmer in high-mass than in low-mass regions.The duration argument is supported by source counts(Garay&Lizano1999).
In recent years,several multiply deuterated molecules have been detected toward dense molecular cores:D2CO,D2CS,ND2H,D2S,CHD2OH,ND3, CD3OH,and D2H+(see Ceccarelli et al.2007for references).Th latest addi-tion to this list,after extensive searches,is the discovery of interstellar D2O (Butner et al.2007).The low fractionation of H2O compared with other molecules suggests that deuterium enrichment is primarily a gas-phase process.The likely origin of multiply deuterated molecules is transfer of deuterons from H+3isotopo-logues at low temperatures(<～20K),aided by transfer from deuterated CH+3and C2H2+at higher temperatures(Roue?et al.2007).The measured abundances of multiply deuterated molecules imply that the freeze-out of molecules onto grains is slow,suggesting grain growth in pre-stellar cores(Flower et al.2005). Warm gas:H2O There are three formation routes for interstellar water.At low temperatures,H2O is produced in the gas phase by dissociative recombina-tion of H3O+,which itself derives from O by reactions with H+3and H2.However, H2O is created much more e?ciently on the surfaces of dust grains by H atom addition to adsorbed O atoms.The ice mantles may desorb from the grains if they are thermally heated to T>～100K by nearby young stars,or through pho-todesorption in regions with signi?cant ultraviolet radiation(Hollenbach et al. 2007).At high temperatures(>～250K),H2O is produced e?ciently in the gas phase through the reactions of O and OH with H2,which have signi?cant barriers (Wagner&Gra?1987).
Far from embedded young stars,dense molecular cloud thus have a back-ground level of H2O originating in H3O+recombination and photodesorption of H2O ice;it is this H2O which is picked up in large-scale maps of H2O emission (Melnick&Bergin2005)although excitation e?ects may complicate the picture (Poelman et al.2007).Close to young stars,the H2O abundance rises steeply because of thermal ice evaporation.Even higher H2O abundances are reached in out?ows,where gas is shock-heated to several100K and the neutral-neutral channel kicks in(Franklin et al.2007).Because of these e?ects,H2O acts as a ?lter for warm gas in star-forming regions.
One application of this?lter is the search for massive circumstellar disks. High-mass stars may form through disk accretion like their low-mass counter-parts,perhaps with an increased accretion rate.The alternative model where high-mass stars form through coagulation of lower-mass stars or pre-stellar cores probably only applies to a minority of cases,as extremely high stellar densities are required.However,positive evidence for accretion disks around young high-mass stars has been hard to?nd,as reviewed by Q.Zhang(this volume).The
Chemistry of star-forming regions5 main problem is confusion of the molecular line emission from the disk with that from the surrounding envelope.
Observations of the H182O line at203GHz with the Plateau de Bure Interfer-ometer have now revealed such a massive circumstellar disk(Van der Tak et al. 2006a).The disk radius is≈400AU,the mass of≈0.8M⊙is≈5%of the mass of the central star,and the observed velocity gradient in the H182O line is con-sistent with the Keplerian rotation speed.Together with NGC7538IRS11 (Sandell et al.2003)and IRAS20126(Cesaroni et al.2005),this source is one of the more compelling cases for an accretion disk around a young high-mass star.
Shocked gas:SiO The star formation process entails gas parcels moving both inward and outward,and shocks occur frequently.The shocked gas has its own chemistry,because the gas is heated to～1000K,grain mantles are disrupted,and even grain cores are shattered if the shocks are fast enough.The erosion of the grain mantles leads to observed enhancements of,e.g.,CH3OH (Bachiller et al.2001),while the grain cores‘sputter’refractive atoms such as Si and Fe.Neutral-neutral reactions in the hot gas then transform these atoms into,e.g.,SiO,which is widely used as tracer of out?ows(Mart′?n-Pintado et al. 1997),and the recently detected SiN and FeO molecules(Walmsley et al.2002; Schilke et al.2003).
4.Galactic Variations in Cosmic-Ray Flux
The ionization fraction of molecular clouds determines the e?ciency of mag-netic support against their gravitational collapse,and also sets the time scale for ion-molecule chemistry.In star-forming regions,the bulk of the matter is shielded against ultraviolet radiation,and cosmic rays are the main ionization source.Only very close to embedded stars,photo-ionization plays a role,as re-cent detections of CO+and SO+testify(St¨a uber et al.2007).Cosmic rays in?u-ence molecular abundances not only through their total?ux,but also through their energy spectrum,in particular the ratio of H-to He-ionizing particles (Wakelam et al.2006b).
Observations of molecular ions show signi?cant variations in the cosmic-ray ionization rateζwithin our Galaxy.Submillimeter emission data of HCO+ toward a sample of seven high-mass star-forming regions at distances of1–4kpc indicateζ～3×10?17s?1(Van der Tak&van Dishoeck2000).This number is in good agreement with measurements of low-energy cosmic ray?uxes by the Voyager and Pioneer spacecraft(Webber1998).However,observations of DCO+ in nearby(0.1kpc)starless molecular cores indicate an ionization rate reduced by a factor of～10from this value(Caselli et al.2002).On the other hand,10×larger ionization rates are found from H+3absorption data on the nearby(0.3kpc)ζPer cloud(McCall et al.2003;Le Petit&Roue?2006),and especially toward the Sgr A region near the Galactic center(Oka et al.2005).Enhancedζ-values near the Galactic center are also reported from H3O+observations of the Sgr B2 cloud Van der Tak et al.(2006b),but the derived ionization rate is lower than that from H+3.
6Floris van der Tak
At least two e?ects appear responsible for the observed variations.First,
the cosmic-ray?ux appears to decrease by a factor of～10from the inner
to the outer Galaxy,as corroborated by synchrotron,X-ray andγ-ray data (Yusef-Zadeh et al.2007).Second,scattering of cosmic rays o?plasma waves appears to cause the di?erence between di?use and dense clouds.This process is
more e?cient in denser clouds with stronger magnetic?elds,in agreement with
the observations.However,other mechanisms may also play a role.Observa-
tional estimates ofζin regions with known magnetic?eld strengths will help to
make progress on this front.
The recent detections of interstellar and circumstellar C4H?,C6H?and
C8H?mark the discovery of negative ions in space(McCarthy et al.2006;Remijan et al. 2007;Cernicharo et al.2007;Br¨u nken et al.2007;Sakai et al.2007).The large electron a?nities of hydrocarbon chains makes the anionic species almost as abundant as the neutral species(Herbst1981;Millar et al.2007).The total abundances only imply a small shift of negative charge,so that the above es-timates of the ionization rates of star-forming regions are not a?ected.The negative ions are useful though,because combined with measurements of the
H I21cm line,the abundance ratios C n H?/C n H may be used to estimate the electron abundances in dark clouds(Flower et al.2007).
5.E?ects of Protostellar Irradiation
During their main sequence phase,high-mass stars emit～10?7of their luminos-
ity in the form of X-rays,which originate in wind shocks.X-ray observations of
star-forming regions mainly probe the low-mass population,which emits X-rays
due to magnetic and accretion activity(see review by Feigelson et al.2007).The
onset of X-ray emission from high-mass stars is hidden from our view,because
of obscuration by the surrounding material.However,the protostellar X-ray emission may be probed indirectly through its e?ect on the chemistry of its molecular envelope.
Benz et al.(2007)have imaged the CS and SO submillimeter line emission
from the young high-mass star AFGL2591with the SubMillimeter Array.The
data show a pronounced‘jump’in the SO abundance by a factor of～100at a radius of～1000AU.Model calculations by St¨a uber et al.(2005)show that such
a jump is evidence for protostellar X-ray emission.Models with ice evaporation
but without X-rays do not?t the data.The derived L X is～10?6of the total luminosity of AFGL2591,which is somewhat higher than for main sequence objects.Possibly the stellar winds of high-mass protostars are stronger than
those of main sequence stars,or additional X-ray emission is generated in the interaction of the wind with the surrounding envelope.
6.Prospects
The year2008will see the launch of ESA’s Herschel satellite,and?rst data are expected in early2009.Unhindered by the Earth’s atmosphere,this mission
will make a major and unique contribution to astrochemistry,especially with its spectrometer HIFI which covers the480–1250and1410–1910GHz ranges at a
Chemistry of star-forming regions7 resolution better than1km s?1.The highlights of HIFI science will be,from an astrochemical point of view:
?unbiased spectral surveys of several Galactic star-forming regions,which provide inventories of their molecular composition;
?large-scale maps of the H2O emission from dense clouds,and detailed multi-line studies of the H2O abundance distribution in star-forming re-gions;
?precise measurements of the O2abundance in dense clouds,PDRs and other environments;
?measure the abundances of interstellar hydrides such as NH,a cornerstone of nitrogen chemistry(which is poorly known because N0does not have ?ne structure lines and N2has no rotational lines.);
?make an inventory of the major carbon and oxygen species in external galaxies,to study chemistry under more extreme conditions(including metallicity)than our Galaxy o?ers.
And just when the Herschel data will have been digested,ALMA operations will get in full swing.One byproduct will be lots of‘accidental’astrochemists, who?nd their submillimeter spectra full of unexpected spectral lines around the line they were interested in.This reviewer hopes that these researchers will evolve one day into‘active’astrochemists.
Acknowledgments.The author thanks Malcolm Walmsley,Ted Bergin and Chris McKee for useful comments and suggestions.
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发动机故障灯亮原因及解决方法 随着汽车技术的发展和环保要求的提高，汽车技术发展非常迅速。然而，令人费解的是，汽车发动机故障灯亮的现象却也越来越多。为了帮助遭遇到这种情况的车主朋友，北京博睿通达技师特总结在此。 一、现象 汽车行驶过程中，或者汽车打火的瞬间，仪表板上的汽车发动机故障灯亮起，通常为红灯或黄灯，一旦亮起，大多数情况下不会自动消失，少数情况下会自动消失，这就是所谓的发动机故障灯亮。 二、发动机故障灯亮的表面原因 1、燃烧状态不好 发动机燃烧状态不好是发动机故障灯亮的主要原因。在汽车设计上，为了确保发动机处于良好的工作状态、确保发动机的正常工作寿命，在发动机上设计安装了氧传感器，用于监测发动机燃烧状态，一旦发动机燃烧状态不好，比如碳氢化合物气体（HC）含量太高一氧化碳含量（CO）太高、氮氧化物（NO）含量太高，这些都是不好的燃烧状态，不仅污染环境，也会造成燃油浪费和发动机过度磨损。 以上各项指标分别意味着： 碳氢化合物（HC）：未经燃烧的燃油成份； 一氧化碳（CO）：未充分燃烧的燃油成份，该物质对人类健康有较大的损害，一氧化碳中毒可致人中毒死亡； 氮氧化物（NO）：在发动机内过高温度下产生，表明发动机磨损加剧，在大气中会污染环境。 2、发动机爆震 发动机另有一个专门的爆震传感器，专门监测发动机爆震。发动机爆震已经意味着有可能带来发动机严重的机件损害或者严重的动力损失。通常情况下，爆震分为有感爆震和无感爆震，在无感爆震的情况下，发动机电脑会根据监测到的情况调整发动机控制参数，避免带来更大的不良影响，但当无感爆震已经超过了发动机电脑可以调整的范围时，发动机故障灯也会点亮报警。 汽车驾驶员对于爆震的主观感受通常有三种情况：第一种情况：汽车无力； 第二种情况：汽车无力，发动机噪音过大；第三种情况：明显有敲缸声音。 在第一种情况下，有的发动机故障灯会亮，有的不会亮，在第二种和第三种情况下，发动机故障灯必然会亮起。 三、发动机故障灯亮的内在原因 1、燃油质量不好 很多发现发动机故障灯亮的车友都有一个感觉：那就是加到一箱油后发动机故障灯突然就亮了。因为发动机对于油的质量指标是有要求的，尤其是随着各处规范对发动机的要求越来越高，那么对油的质量指标也就要求越来越高。比如说，以前的汽车发动机通常压缩比都在7.0以下，而现在的汽车发动机压缩比通常都在10.0以上，这种情况下，一般都要求辛烷值95号以上的汽油。当然，除了这个燃油标号以外，还有其它一些技术指标也十分重要，因为技术性太强，就不一一列举了。然而，在实际生活上，毕竟有一些加油站并不能完全按规范提供满足高性能发动机的燃油，这就导致了发动机故障灯亮时有发生。 2、发动机汽
发动机故障灯亮是什么原因车突然熄火 汽车发动机常见故障及排除方法当汽车发动机 工作不正常，而自诊断系统却没有故障码输出时，尤其需要依靠操作人员的检查、判断，以确定故障的性质和产生故障的部位。笔者现将汽车发动机常见故障总结为以下： 1.1 发动机不能发动（1）故障现象：打开点火开关，将点火开关拨到起动位置，发动机发动不着。（2）故障产生的可能原因： A.起动系统故障使发动机不能转动或转动太慢：①蓄电池存电不足、电极桩柱夹松动或电极桩柱氧化严重；②电路总保险丝断；③点火开关故障；④起动机故障；⑤起动线路断路或线路连接器接触不良。 B.点火系统故障：①点火线圈工作不良，造成高压火花弱或没有高压火花；②点火器故障；③点火时间不正确。 C.燃油喷射系统故障：①油箱内没有燃油；②燃油泵不工作或泵油压力过低；③燃油管泄漏变形；④断路继电器断开；⑤燃油压力调节器工作不良；⑥燃油滤清器过脏。 D.进气系统故障：①怠速控制阀或其控制线路故障；②怠速控制发阀空气管破裂或接头漏气；③空气流量计故障。 E.ECU故障。（3）诊断排除方法和步骤。①打起动档，起动机和发动机均不能转动，应按起动系故障进行检查。首先，检查蓄电池存电情况和极柱连接和接触情况；如果蓄电
池正常时，检查起动线路、保险丝及点火开关；②踏下油门到中等开度位置，再打起动机。如果此时，发动机能够发动，则说明故障为怠速控制阀及其线路故障或者是进气管漏气，如果踏下油门到中等开度位置时，仍然发动不着，应进行下一步骤的检查；③进行外观检查。检查进气管路有无漏气之处；检查各软管及其连接处是否完好；检查曲轴箱通风装置软管有无漏气或破裂；④检查高压火花。如果高压火花不正常，应检查高压线、点火线圈、分电器和电子点火器；⑤检查点火顺序是否正确；⑥检查供油系统的供油情况。在确认油箱有泪的情况下，检查燃油管中的供油压力；⑦检查点火正时及各缸的点火顺序；⑧检查装在空气流量计上的燃油泵开关的工作情况；⑨检查各缸火花塞的工作情况；⑩检查点火正时。如点火正时不正确，应进一步检查点火正时的控制系统；?B11?检查ECU的供电情况和工作情况，确定是否是ECU的故障。 1.2 发动机失速故障（1）故障现象：发动机工作时，转速忽高忽低，这种现象即为发动机失速现象，其故障被称为发动机失速故障。（2）故障原因：造成发动机转速忽高忽低的原因有燃油喷盘系统的故障，也有点火控制系统的故障，还有进气系统的故障。常见的故障原因有以下几点：①进气系统存在漏气处。如各软管及连接处漏气，PVC阀漏气，EGR系统漏气，机油尺插口处漏气，机油滤清器盖漏气等；②空气滤清器滤芯过脏；
油改气发动机故障灯亮排除方案 车改气以来,不管是烧油烧气都表现良好,由于平时气很容易启动,所以基本用气启动,忽略了烧油,前几天想要跑长途才想起烧油试一下,发现虽能顺利启动,但怠速不稳,踏油门发动机转速上不去并伴有回火放炮,因此而烧坏了空滤芯. 自己清洗了油嘴及节气门,启动运行都正常,感觉发动机ECU认气反而不认油,关闭钥匙拆下电瓶5分钟使发动机ECU 清零复位,再用油启动运行,一切又恢复正常,虽然改掉了用气直接启动的习惯,每天坚持用油跑十几公里,但隔了几天又旧病复发. 上网查询了类似问题,得到了一些启示, 经分析可能是仿真器与氧传感器未能连接而导致的,仿真器有两个作用,一是在烧气时切断四个油嘴,既防止油气混烧又能使四个油嘴在烧气时停止工作,从而延长油嘴寿命,二是烧气时向发动机ECU模拟一个脉动信号,欺骗发动机ECU,使发动机ECU感觉烧气也是在烧油,从而发出正确指令. 国庆放假,我自己亲自动手,先找到氧传感输出与发动机ECU的连接线,测了一在烧油状态下,氧传感向发动机ECU输出的直流在0--1V之间波动,每10S约7次左右,这与我查得的氧传感器相关数据相吻合,烧气时由于已切断四个油嘴,此时发现氧传感器向发动机ECU输出的电压在0.1V左右,根本不脉冲,这也是好多朋友改气后发动机故障灯SVS亮的原因,将氧传感器输出与发动机ECU的连接线剪断,然后将仿真器的两根线分
别与氧传感输出端及发动机ECU输入端连接,也即使说将仿真器与氧传感器连接的两根线串接在仿真器与氧传器之间,第一次连接后测量仿真器向发动机ECU输出的电压在0.1v左右且固定不动,是一个定值不是波动信号,观察发动机故障灯SVS亮,猜想可能是以上四条线接反的原因,遂将仿真器原接氧传感器的线改接到发动机ECU输入端,将仿真器原接发动机ECU输入端改接氧传感器的输出端,重新测试:在烧油模式下氧烧油模式下氧传感器向发动机ECU传感器向发动机ECU输出的直流仍就在0--1V 之间波动,每10S约7次左右,烧油正常,在烧气模式下氧传感器向发动机ECU输出电压变为在0.5-0.8之间波动,观察发动机故障SVS灯,也不再亮起,用油启动用气启动都一次成功,上路测试油气状态下出力都非常好,如果不看转换开关的状态,老实说自己都不清楚到底是在烧油还是在烧气 灯SVS亮的现象. 我们重庆油改气虽装有仿真器 发动机ECU相连SVS亮的现象 传感器和发动机ECU可接可不接责
发动机故障灯亮原因分析及解决方法 随着汽车技术地发展和环保要求地提高，汽车技术发展非常迅速.然而，令人费解地是，汽车发动机故障灯亮地现象却也越来越多.为了帮助遭遇到这种情况地车主朋友，特总结在此. 一、现象 汽车行驶过程中，或者汽车打火地瞬间，仪表板上地汽车发动机故障灯亮起，通常为红灯或黄灯，一旦亮起，大多数情况下不会自动消失，少数情况下会自动消失，这就是所谓地发动机故障灯亮. b5E2R。 二、发动机故障灯亮地表面原因 、燃烧状态不好 发动机燃烧状态不好是发动机故障灯亮地主要原因.在汽车设计上，为了确保发动机处于良好地工作状态、确保发动机地正常工作寿命，在发动机上设计安装了氧传感器，用于监测发动机燃烧状态，一旦发动机燃烧状态不好，比如碳氢化合物气体（）含量太高一氧化碳含量（）太高、氮氧化物（）含量太高，这些都是不好地燃烧状态，不仅污染环境，也会造成燃油浪费和发动机过度磨损. p1Ean。 以上各项指标分别意味着： 碳氢化合物（）：未经燃烧地燃油成份； 一氧化碳（）：未充分燃烧地燃油成份，该物质对人类健康有较大地损害，一氧化碳中毒可致人中毒死亡； 氮氧化物（）：在发动机内过高温度下产生，表明发动机磨损加剧，在大气中会污染环境.
、发动机爆震 发动机另有一个专门地爆震传感器，专门监测发动机爆震.发动机爆震已经意味着有可能带来发动机严重地机件损害或者严重地动力损失.通常情况下，爆震分为有感爆震和无感爆震，在无感爆震地情况下，发动机电脑会根据监测到地情况调整发动机控制参数，避免带来更大地不良影响，但 当无感爆震已经超过了发动机电脑可以调整地范围时，发动机故障灯也会点亮报警. DXDiT。 汽车驾驶员对于爆震地主观感受通常有三种情况： 第一种情况：汽车无力； 第二种情况：汽车无力，发动机噪音过大； 第三种情况：明显有敲缸声音. 在第一种情况下，有地发动机故障灯会亮，有地不会亮，在第二种和第三种情况下，发动机故障灯必然会亮起. 三、发动机故障灯亮地内在原因 、燃油质量不好 很多发现发动机故障灯亮地车友都有一个感觉：那就是加到一箱油后发动机故障灯突然就亮了.因为发动机对于油地质量指标是有要求地，尤其是随着各处规范对发动机地要求越来越高，那么对油地质量指标也就要求越来越高.比如说，以前地汽车发动机通常压缩比都在以下，而现在地汽车发动机压缩比通常都在以上，这种情况下，一般都要求辛烷值号以上地汽油.当然，除了这个燃油标号以外，还有其它一些技术指标也十分重要，因为技术性太强，就不一一列举了.然而，在实际生活上，毕竟有一些加油站并不能完全按规范提供满足高性能发动机地燃油，这就导致了发动机故障灯亮时有发生. RTCrp。
发动机故障灯亮了有快一年了，这期间感觉车冷车启动有点难（哈尔滨冬天户外很冷）、噪音大了、油耗高了，别的倒也没设么。 只是每天看着那个黄色的小灯一直亮着，心里总是不舒服。 去了两次，也打电话问过市里交通台的大侠，问题均未得到解决。 电台里的大侠只是说如不影响开车就让它亮着吧，好多车都是这样，不好解决，或者到查查，用电脑检测并清一下。 去了两次，修车的小师傅很认真很肯定的用电脑检查了几次（期间碰到一位记者朋友，也是，也发现了故障灯亮的问题，不过他的车进到维修间见到小师傅后竟然奇迹般地自动好了。 羡慕）说什么，进气过稀、油气过浓什么什么的一堆我记不住的故障原因后，又说检测不到前氧传感器的信号，让换一个前氧传感器就行。 在我的追问下，信誓旦旦的保证说换后肯定好。 。 换一个前氧传感器几多大米？回答是温柔的多米，加工时费。 我靠真要奉劝那些抢劫犯从良了，真的别满大街抢劫越货了，风险太大，还是开个得了。 遮风挡雨还安全得理直气壮地明抢，多惬意呀！直接，闪。 上网，淘宝、论坛、溜了好几圈。 最后在论坛娜娜美女版主的帮助下，淘了一个前氧传感器，好像是还是多米吧，记不清了，半年前的事了。 之后一直忙，没顾得上换。 这不，冬天来了，天冷了。 想到上一个冬天冷车启动事，还是找了个时间，在家附近的一个修车小店让小师傅换了机油后，顺带帮忙换上新的前氧传感器，断电，恢复，着车。 呵呵，问题解决了！可是好景不长，晚上再次启动，那个小黄灯又顽强地亮了起来。 无奈，上网，进到咱的坛子里，继续游哇游。 看到了大侠的帖，深受启发。
第二天跑到单位，找到十字螺丝刀，温柔几下，问题搞定。 至今已有一周时间，问题彻底解决。 仔细总结了一下，最后决定我也要开个，呵呵免费。 借用大侠的图片详细说一下问题解决的方法。 首先，熄火，打开前机盖，找到下图中在空滤盒子左侧的空气流量计，用螺丝刀将之卸下，很简单，一共两个螺丝，外加一个插头（拔下即可，都会的）。 空气流量计卸下后的样子， 用酒精和脱脂棉把你能看到和能摸到的所有地方，擦干净，其实主要就是里面一个看上去有点像一小球松香似的传感器擦干净即可，擦净后是透明的松香颜色，能够看到里面的两根接线。 我当时怕清洗不干净，又把整个空气流量计扔到超声清洗机里，浸泡超声清洗了十几分钟（不用怕，这个东西是全密封的），取出用吹风烘干。 原样装回去。 电瓶断电，秒以上就行，接回电瓶。 打火试试，吼吼，问题彻底解决。 使用一周了，没有任何问题。 把拆下的旧的前氧传感器装回去，还是莫有任何问题，至此问题彻底解决。 总结： 不要轻信和什么砖家，氧传感器轻易是不会坏的，中石油和中石化的
汽车发动机故障灯亮 7大因素 发动机故障灯亮是每位车主都不能够忽视的问题，这直接关系到发动机寿命和行车安全等。盛德世通整理了发动机故障灯亮常见故障原因，通常是由于以下几个原因造成：
1.汽油品质差，不达标 计大部分车主都有这个经历，车子加完油不久，汽车仪表盘上就亮起了发动机故障灯；这一般是因为在不规范的加油站加了质量较差的汽油，导致发动机工作时油气混合气燃烧不充分，发动机故障灯亮。这不会影响行车安全，但或多或少会对发动机造成危害。 2.氧传感器故障 如今汽车上安装有两个氧传感器，三元催化器前后各放一个。前氧传感器的作用是检测发动机不同工况的空燃比，同时ECU电脑根据该信号调整喷油量和计算点火时间。后方的主要是检测三元催化器的工作好坏！所以如果氧传感器损坏或者传感器插头损坏、松动，会导致混合气过稀或过浓，从而引起故障灯亮。
而实际上，氧传感器是一个相当耐用的部件，只要燃油质量过关，它可以使用3年或更长的时间。所以新车的故障灯亮，不妨查看一下氧传感器插头是否松动。 3.空气流量传感器故障 空气流量传感器也称为空气流量计，它检测吸入的空气量转换成电信号传递给电控单元ECU，根据最佳空燃比，间接让ECU决定喷出多少燃油。如果空气流量传感器或线路出现故障，ECU将得不到正确的进气量信号，就不能进行正常的燃油量控制，从而造成混合气过稀或过浓，发动机无法正常工作。
虽然空气流量传感器失常不至于造成发动机无法启动，但诸如怠速不稳、加速不良、进气管回火以及排气管冒黑烟等现象还是极有可能的。 4.火花塞积碳 市面上质量参差不齐的燃油和拥堵的城市交通使得汽车火花塞很容易产生积碳，火花塞积碳会导致发动机工作不良，出现启动困难、怠速不稳、加速不良、急加油回火、尾气超标、油耗增多等不正常现象。 5.发动机爆震
故障案例： L462发动机故障灯点亮 提报人：SHK 马绍威 车型L462 车架号码发动机 3.0SC 行驶里程9653KM 购买日期2019.7.15 维修日期2020.4.2 故障现象确认： 1 ，车辆进场时发动机故障点亮。发动机无抖动现象 2，故障出现在车辆热车状态。且发动没有高温。 读取故障内容及SDD指导建议关键故障码的冻结值： 1，使用PF读取DTC,车辆PCM内有多个故障码。 2，故障代码P013A-00，P013A-00,P0333-22,P0496-00,P128-00 系统结构图及电路图：
诊断思路： 1 ，根据各个故障码，怀疑有三个故障可以导致发动机灯亮。 2 ，P013A-00,P0496-00,P0128-00 3，由于多个故障导致灯亮。建议清除故障码再测试 检测过程： 1，检查机油液位正常，使用探路这测试车辆EVAP空气净化阀，测试通过。 2，清除故障代码，出去试车100KM,后故障灯再次点亮。进场读取故障代码为P0128-00 3，根据故障指引，清除故障后再次出现，直接更换节温器。更换节温器后试车故障再次出现。 4，检查换下来节温器未发现全开，后来仔细询问客户仪表水温指针有无变化，客户说低于中间刻度线。 5，读取发动机冷却液温度，发现冷却液传感器1温度最高时才75度。冷却液传感器2最高时83度。 6，再次怀疑水温传感器1不准确，拆下水温传感器1测量都在正常温度下传感1的阻值为78千欧，正常水温传感器电阻为38千欧 7,，试车故障排除 相关故障部位图片、数据流及分析：
故障障原因分析： 1，一味以故障码指引来检查，没有深层次的分析两个水温传感器的关联性，导致走弯 路。返修。 故障处理办法： 1，更换节温器，更换水温传感器 专用工具设备： 1,诊断电脑，万用表 案例点评及建议： 此故障的关键点在于P0128-00的理解,该DTC在Topix上的维修指导误导了 经销商.P0128-00指向的是冷却液温度低于节温器调节的温度.在这里,需要 理解节温器是如何调节温度的,PCM又如何知道节温器调节的温度是否达到呢?
【案例】科雷傲发动机故障灯亮故障排除 关键词 前氧传感器 故障现象 一辆2009年产雷诺科雷傲，搭载2.5 L自然吸气发动机和CVT变速器，行驶里程26万km。用户反映车辆行驶中发动机故障灯亮、ESP灯亮，而且在ESP灯亮后，车辆无法再提速，发动机转速限制在1 500 r/min左右。 检查分析接车后，笔者通过与用户进行沟通，了解到该车故障出现有偶发性。观察车辆仪表板发现，在怠速情况下，发动机故障灯亮，没有其他系统警示灯亮及异常指示。为了确定基本的故障信息，首先用故障诊断仪对车辆进行检测，在发动机控制单元中存有5个故障，如图1所示。 图1 发动机控制单元中存储的故障码 根据故障码，笔者先打开发动机舱观察前氧传感器的外观及线束，发现该车前氧传感器已经更换过，且接线端跟另一侧直接短接。这说明该车故障在其他地方已经做过处理，但故障未排除。检查加速踏板位置传感器时，发现该传感器也被更换过。关于制动灯开关信息不一致的故障码，观察制动踏板处的制动灯开关，发现没有被拆卸的痕迹。对于DF1012巡航控制的故障码，是由于以上其他故障发生后，巡航限速给出的故障码，没有参考意义。 针对以上几个故障码，笔者先对氧传感器故障进行诊断处理：读取前氧传感器的数据，发现该传感器在发动机各个工况下都没有数据变化；测量氧传感器的供电及搭铁情况，都没问题；测量到发动机控制单元的信号线，连接良好。既然没有数据变化，连接良好，那么说明传感器已经损坏。氧传感器损坏，虽然会导致发动机故障灯亮，但不会导致发动机无法加速问题。 为了验证车辆确实存在无法加速的问题，笔者根据用户描述的工况进行试车，未发现无法加速的情况。为了更好地解决故障灯亮问题，笔者先更换前氧传感器后消除故障码，然后观察加速踏板位置传感器数据，发现不存在数据失真的问题。 为了一次性解决该车故障，笔者对车辆进行反复试车，发现在打开空调运行5 min 左右后，发动机控制单元数据流中冷却液温度不断上升到105℃，空调压力传感器数据也不断的上升到4.09 V，而最大值为4.16 V。然后观察冷却风扇工作情况，发现电子扇的副风扇，在空调开启瞬间，工作大约十几秒后就开始减速，直到停止，主风扇还可以正常运转。为了确定电子扇的高中低速运转情况，笔者用
【摘要】：一辆行驶里程约km的本田奥德赛RB3。此车前部因交通事故进行了修复, 事故修复后发动机故障灯异常点亮,维修人员清除相关故障代码后交车, 大概半个月后发动机故障灯又亮了。 接车后通过H DS 检测仪读取故障代码,为P0 7I 1一燃油系统过稀故障。为进一步查清故障原因,调取故障发生时ECM 中的数据进行分析。 可以看出故障发生时发动机的工作情况, 发动机转速为78 1 r/l llin、车速为6 kmhl 、进气压力传感器(M A jP值为4 kPa 、空气流量传感器(M A )F 值为.49 沙、节气门位臵(T)P 传感器值为0.7 8 V 、加速踏板位臵(AP)P 传感器值为OV ,根据此时A PP 传感器和TP 传感器的数值可以看出加速踏板和节气门均处于完全关闭的状态,此时发动机处于怠速运转。而M A P 和M A F 的数值偏高,说明此时发动机处于有负荷的工况,综合以上信息,可以确定车辆刚刚起动。再看看和燃油系统相关的几个参数的工作情况, 短其燃油修正1ST)和长其燃油修正(TL )分别为1.21 和1.25 ,这两个数值是PCM根据空燃比传感器反馈的信号对喷油脉宽进行相应的调整。正常时,这两个数值应该都在l 左右波动,PCM 会根据空燃比传感器反馈的信号进行喷油脉宽调整, 以尽量保证闭环工况时燃油混合气接近理论空燃比。ST 数值大于1说明燃油混合气偏稀.PCM 在增加喷油脉宽;ST 数值小于1说明燃油混合气偏浓,PCM 在减少喷油脉宽。TL 数值则是根据ST 数值的平均值得来的。测出的ST 数值和TL 数值均大于l,说明此时空燃比传感器反馈空燃比过稀,PCM 输出信息在增大喷油脉宽,加大喷油量。 接下来, 将故障代码清除,对车辆进行了路试,经过路试确认车辆提速良好, 动力充沛, 可以初步判断车辆在行驶过程中燃油
福克斯发动机故障灯无故点亮 汽车维修案例 故障现象： 一辆长安福特福克斯1.8 L自动挡轿车，行驶里程4.26万km。据用户反映，发动机故障灯在行驶过程中点亮，但车辆行驶没有感觉异常。 故障分析： 使用故障诊断仪IDS调取故障码，显示混合气过稀。该车进气计量采用进气压力传感器，分析造成混合气过稀的原因主要包括：油路问题(包括燃油、油泵以及喷油器等)、MAP传感器故障、氧传感器故障、动力系统控制单元PCM故障或控制线路故障以及燃烧室积炭等。查询车辆维修记录，1个月前做过发动机深层除炭、全车油路清洗、进气系统清洗以及三元催化器清洗，因此可以排除积炭的可能性。进行路试，车辆行驶正常，这说明油路有问题的可能性也比较小。 将可擦写存储器KAM值清零，重新起动发动机，进入闭环工作模式后氧传感器一直处在低电压，此时燃油短期修正SHRTFT一直在增加喷油，当SHRTFT修正达到最大值时，长期修正LONGFT就开始修正基本喷油量，以达到精确喷油控制。SHRTFT和LONGFT在清除KAM之后能够根据当前的工作情况重新学习KAM值，这就说明PCM和控制线路没有出现问题。会不会是氧传感器被污染造成氧传感器响应速度过低，使PCM接收到错误的信号呢?更换新的氧传感器，混合气还是显示过稀。排除以上可能的故障因素，故障点就主要集中在MAP传感器了。
使用IDS读取数据流，可以看到BARO的压力值(大气压力)低于正常的水平，正常应该是在101 kPa左右，而2次读取数据流却显示了不同的大气压力值。会不会是MAP传感器计量偏差造成进气计量出现错误呢?更换MAP传感器之后，试车问题依旧存在。因为之前已经排除了其他的故障可能，只剩下燃油质量是最大的疑点了。 故障排除： 更换原车的汽油并清洗油箱，清除KAM值后，SHRTFT和LONGFT恢复正常。跟踪回访确定故障不再出现。
发动机故障灯亮的原因分析 随着社会的进步，生活水平的提高，私家车的拥有量成倍数成长，车辆故障也就越来越成为了人们所关注的焦点，车辆的故障形式多样、原因各异，其中让车主头痛的而且易发生的便是发动机故障灯亮。 发动机故障灯亮的原因可以从发动机构成的系统进行分析：燃油供给系统、点火系统、进气系统、排气系统及各传感器部件。 燃油供给系统： 燃油供给系统主要包括油箱、油泵、管路、汽油滤清器、碳罐、碳罐电磁阀、燃油压力调节器、喷油咀等。 油质是导致发动机故障灯亮的首要因素，大家知道汽油的抗爆性是用辛烷值来表示的，辛烷值越高，抗爆性越好，比如97号车用汽油，其辛烷值不小于97（研究法），含铅汽油会导致氧传感器铅中毒，因而油质是导致发动机燃烧不足的主要原因，从而也是导致故障灯亮的原因之一。 油泵的供油压力达不到一定的压力，会导致喷油咀雾化程度不好，从而影响发动机的正常工作。正常情况下油泵压力在2.5—3.5MPA之间，如果油泵压力大于3.5MPA，当喷咀工作后，喷咀弹簧很难克服油压，导致继续喷油，引发尾气过浓。 喷油咀是由电磁阀线圈、针阀、磁铁、弹簧、喷孔等组成，当通电时，电磁线圈产生吸力，针阀吸起，打开喷油孔，燃油经喷油孔呈雾状喷出，正常情况下电磁线圈阻值为15Ω左右。因而喷油咀的好坏直接影响发动机的工况；雾化程度好，燃烧完全，发动机工作平稳、有力，反之发动机发抖，尾气过浓。更严重的是喷油咀滴油，直接导致发动机排气管有可能冒黑烟导致氧传感器报警，点亮发动机故障灯。 碳罐电磁阀是否正常工作也是点亮发动机故障灯的原因之一。碳罐电磁阀是由管接头，阀门，铁心，回位弹簧，电磁线圈组成，它是一种NF常闭电磁阀，电磁阀只有在发动机水温达到摄氏60度时，发动机运转，发动机电脑ECU以占空比的形式控制电磁阀开启以释放油粒，从而燃油蒸气被吸入进气管。根据发动机运行工况，电磁阀接受ECU指令来控制进气量，如果电磁阀阀门被卡住，使电磁阀常开，从而使进入进气管的气体变浓，最终导致发动机
【摘要】：一辆行驶里程约km的福特锐界3.5L轿车。车主反映：车辆出现发动机故障灯亮的现象,发动机故障灯亮后车辆一直正常行驶, 发动机也没有出现抖动的现象。 接车后,连接IDS 检测仪对发动机系统进行检测, 检测仪显示有P40 03 :0 0一EC) PCM 故障代码, 故障说明为三元催化转化器效率低于临界值(第2 排)。对车辆进行初步检查后发现,车辆只是发动机故障灯亮并没有其他异常, 于是清除故障代码后试车,发动机故障灯未点亮。因此判断可能是燃油品质的原因,询问车主最近加油的情况。车主反映车辆一直加97 号汽油, 最近一次在外地加油站加过一次93 号汽油, 然后就出现了发动机故障灯亮的故障。按照福特锐界车的要求,加39 号汽油是能满足该车的使用要求的, 分析可能是加油站的燃油品质有问题, 建议车主继续加97 号汽油观察一段时间。4 天后车主反映车辆又出现了发动机故障灯常亮的情况, 再次检测还是同样故障代码,车主强调车辆这次是在定点加油站加的97 号汽油,于是排除燃油品质的原因。 断续分析认为, 喷油器漏油、发动机线路故障、汽油蒸汽排放控制系统(E VA)P 故障、氧传感器故障及三元催化转化器故障等均可能造成发动机故障灯点亮, 于是按照故障出现的可能性逐步对车辆进行检查。 拆卸油轨及火花塞, 发现油轨内无杂质, 喷油器也无滴漏现象,火花塞的颜色为赤褐色,表明火花塞正常。对发动机线路外观进行检查,各线路无裸露, 导线连接器连接正常,无松动现象。根据故障代码对车辆进行定点测试。用检测仪检查车辆O B D 系统,正常;燃油经济性检测和动力平衡检测也均未发现异常;通过检测发现该车EVA P 正常;检测怠速状态下发动机数据流中的氧气传感器的数值, 发现该车数据流下游氧传感器电压偏高,由此