Exhaust Gas Recirculation (EGR) system is a part of the vehicle emission control. It directs a portion of exhaust gases back into the engine intake to lower the combustion temperature, read more below. The code P0400 is set when the EGR system flow is less than expected. Usually this happens when carbon deposits (soot) clog up the EGR system passages and tubes. There might be some driveability concerns, such as, surging, poor fuel economy, rough idle, but in some cases there could no noticeable symptoms at all. In some vehicles, if the EGR system doesn't work, there might be some engine pinging (detonation) noticeable on acceleration or under load (e.g. when driving uphill). It really depends on the cause. If the code P0400 is caused by some minor issue like a faulty EGR temperature sensor and the EGR system works properly, there should be no problem driving. However, if the EGR system doesn't function properly, the combustion temperature will be higher, which in a long run could cause engine damage.

- clogged or restricted EGR passages - sticking or clogged EGR valve - problem with EGR valve position sensor - cracked or restricted vacuum line to the manifold absolute pressure (MAP) sensor - clogged catalytic converter - carbon deposits (soot) on the EGR temperature sensor (Nissan) - faulty mass airflow sensor (MAF) - open or short in the EGR temperature sensor circuit - mis-routed vacuum lines - electrical problem with the EGR valve control circuit - engine computer problems - On many 90's and early 00's Nissan vehicles (e.g. Pathfinder, Altima, Maxima, Frontier, Quest) the code P0400 could be caused by a carbon buildup blocking the air flow around EGR temperature sensor. The repair involves removing and cleaning the EGR temperature sensor an the EGR tubes, ports and passages. A service bulletin for the 1998-2002 Frontier and Xterra with a 2.4L 4-cylinder engine recommends cleaning the EGR port in the intake manifold; the EGR port plugs need to be removed.

- In the 90's and early 00's Mazda cars and trucks, the code P0400 could be caused by clogged EGR passages, often in the throttle body. The repair also involves cleaning the EGR passages. Similarly in the 90's Chevrolet Tracker or its twin Suzuki Sidekick/Vitara, the clogged EGR passages in the intake plenum and the back side of the throttle plate can cause the code P0400. The repair involves checking the EGR operation with a scan tool and if the idle doesn't change when the EGR valve is commanded open, checking and if needed cleaning the EGR passages. - A clogged EGR tube was a common case for the code P0400 in some late 90's Mercedes-Benz cars. To clean the EGR tube, the EGR valve needs to be removed. This thread has some very descriptive photos. The most often found problem with the EGR system is carbon buildup restricting the EGR flow. Usually, if a carbon buildup is found in one part of the EGR system, the other ports and passages could be clogged too, so the entire EGR system needs to be checked for restrictions and cleaned if needed to fix the problem.

Check the vacuum line routing according to the vacuum line diagram. Check the electrical part: the connectors and the wiring to the EGR valves, solenoids and sensors. vacuum cleaner in nigeriaIn Mazda vehicle, the EGR boost sensor and its vacuum hose need to be checked as the sensor could fail or the sensor tube could be restricted or cracked. vax vacuum cleaners for saleIn a Subaru, the BPT valve needs to be checked along with other EGR components. universal vacuum cleaner sparesIf a clogged catalytic converter is suspected, the exhaust back pressure needs to be checked. In Nissan vehicles the EGR temperature sensor clogs up often; it needs to be inspected first. The Exhaust Gas Recirculation (EGR) system redirects a small portion of exhaust gases from the exhaust manifold back into the intake manifold (see the diagram) to lower the combustion temperature.

The engine computer regulates the flow of the EGR gases by opening or closing the EGR valve. The EGR flow is at its maximum during steady highway cruising. The engine computer periodically tests the operation of the EGR system. If the engine computer detects that the EGR flow is less or greater than expected, it sets the fault code P0400 - Exhaust Gas Recirculation Flow Malfunction.» » Delhi choking on foul air, time to clean upJayashree Nandi Your early morning routine of a walk and workout out doors this winter is likely to endanger your health rather than give you any benefits. What you may believe to be fresh morning air is anything but that. There are fine pollutants hanging in the air that get into your lungs, gradually reducing its capacity.And for those who already have a respiratory condition, any strenuous exercise or exposure outdoors is a clear invitation for trouble. Doctors say they should remain indoors during early morning hours to avoid their condition getting aggravated.

According to traditional wisdom, morning air is the purest. In fact, pollutants such as ground-level ozone (O3) are at their lowest level in the morning and peak only later in the day. Ozone, which is also associated with compromised lung function, may impact people towards afternoon. But in Delhi, PM 2.5 levels seem to be peaking in the morning, especially betwe ing, especially between 6 am and 10 am. Scientists attribute this to low temperatures and calm conditions that lower the boundary layer (lowest part of atmosphere), trapping particulate pollution near the surface.The same phenomenon reduces visibility and the city appears to be in a haze. "We are seeing a trend of high particulate pollution from 7 pm to 7 am, sometimes even till 10 am. This is not just because of high emissions but because as it gets colder, pollutants are trapped. It starts getting better once the sun is out and it's relatively warmer," says Gufran Beig, chief scientist at SAFAR, Indian Institute of Tropical Meteorology (IITM), which monitors air quality at ten air monitoring stations in NCR, including Noida.

Delhi Pollution Control Committee's (DPCC) real-time monitoring at six other stations in Delhi reflects the same trend with PM 2.5 hovering around 150 to 200 micrograms per cubic metre, two to three times the national safe standard of 60. India doesn't maintain a national air quality index (AQI) yet but the ministry of environment and forests has launched an AQI that will be operational in a few months. According to the AQI, PM 2.5 levels ranging from 121 to 250 make the air "very poor" and this "may cause respiratory illness on prolonged exposure. The effect may be more pronounced in people with lung and heart diseases." Experts at Centre for Science and Environment (CSE) believe that trucks plying inside the city could be causing an increase in PM levels at night. "I think there are two things happening. Trucks are emitting at night which is leaving even early mornings polluted. The second reason is that nights are very cold which brings down the boundary layer. But our analysis too shows three peaks in air pollution levels — late night, early morning and evening.

There is a slight dip in the afternoon usually," says Anumita Roy Chowdhury, head of CSE's clean air programme. A DPCC official, who didn't wish to be quoted, said: "The condition is quite bad in Delhi, especially in the mornings. I would suggest people speak to their physicians and follow their advice." In Chinese cities where pollution levels are comparable with Delhi, people working outdoors have started using N 95 masks that reportedly filters almost 90% of fine pollution particles. Doctors meanwhile are seeing a steep jump in hospital admissions of patients with chronic obstructive pulmonary disorder and acute bronchitis."People who have any respiratory illness should avoid stepping out early mornings for two reasons—it's cold and it's polluted.We always advise them to go out when its sunny. Every year, we see a 20% to 25% increase in complications associated with respiratory disorders during this time," said Dr Arup Basu, senior consultant, chest medicine, Sir Ganga Ram Hospital.

RISK OF BEING AN EARLY BIRD If you are stepping out early in the morning to catch that fresh air while on a walk, think again. The air quality in the city is very poor, particularly between 5.30am and 10am.The tiny PM 2.5 particles which infiltrate your lungs do the maximum damage. Noon or afternoon, when it's sunny and clear, may be a better idea. The System of Air Quality, Weather Forecasting and Research (SAFAR), Indian Institute of Tropical Meteorology (IITM), also monitors pollution in the city. This was how the graph of hourly averages looked on November 20, 2014 (the latest available) The culprit PM 2.5 refers to tiny particles or droplets in the air that are two-and-a-half microns or less in width. There are about 25,000 microns in an inch. When outdoor levels of PM 2.5 are elevated, staying indoors may reduce your exposure although some outdoor particles will come indoors. Some ways to reduce exposure are to limit indoor and outdoor activities that produce fine particles (for example, burning candles indoors or open burning outdoors) and avoiding strenuous activity in areas where fine particle levels are high -New York state department of health Health impact Numerous scientific studies have linked particle pollution exposure to a variety of problems, including premature death in people with heart or lung disease

, non fatal heart attacks, irregular heartbeat, aggravated asthma, decreased lung function and increased respiratory symptoms, such as irritation of the airways, coughing or difficulty in breathing. People with heart or lung diseases, children and older adults are the most likely to be affected by this. -US EPA Delhi Pollution Control Committee (DPCC), besides other agencies, does real-time monitoring of the pollutants. The following were the half-hourly averages for PM 2.5 (in microgram per cubic metre) recorded by DPCC for Nov 25, 2014, at three stations. (Safe limit is 60 according to National Ambient Air Quality Standard for India) TOI'S 7-POINT ACTION PLAN FOR A LUNGFUL OF PURE AIR Given that Delhi is the world's most polluted city according to WHO, immediate steps are needed to clean up the city's air, some of them pretty radical 1 Make it mandatory for diesel cars to have Euro 5 emission standards. This requires an expensive filter (cost about Rs 1 lakh per car). All new diesel cars - that is around half of all new cars - should conform to Euro 5.

We would suggest so should the older diesel cars 2 Improve quality of diesel. Govt must insist that refineries supply lowsulphur diesel to cities. Euro 5 emission standards require low-sulphur diesel 3 Bring down over 3 years the price gap between diesel and petrol so that the incentive for diesel vehicles is reduced 4 Don't just use a broom to displace road dust from one place to another. Acquire an adequate fleet of mechanized vacuum cleaning vehicles that will suck out road dirt and dump it in designated pits outside the city 5 Enforce the ban on burning dry leaves. This problem is the worst in Lutyen's zone where gardeners of large bungalows tend to burn dry leaves in back lanes 6 Build a world class public transport system so that private cars are fewer on roads. While the Metro is terrific for the city, there has to be effective last-mile public transport connectivity 7 Plant more trees so that Delhi reaches the internationally mandated 33% tree cover for cities. This will bring down dust - a key offender, apart from vehicular emission, for high suspended particulate matter in the Delhi air From Around the WebMore From The Times of India