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I am thinking that you have a 2.2 liter turbo diesel. Very few people with diesel engines come to this place.
Many of the new diesel engines have EGR. When your power demands are low, the valve opens and some exhaust gases are allowed to come into the intake manifold. The turbo is making pressure most of the time, not like a gasoline engine, so there is often more pressure in the exhaust manifold to allow exhaust to flow into the intake manifold. The intake manifold has boost pressure, so this pressure difference is something to understand. The ECU will use vacuum to open the EGR by varying amounts. The ECU probably looks to see that the air flow measured by the mass air flow meter (MAF) drops when the EGR is opened. If the EGR does not open, the ECU sees that the MAF signal did not change, and the ECU will make the engine trouble or engine check light (CEL) come on. So if this happens, it could be the cacuum valve that the ECU controls is not working. Could be a mechanical or electrical problem. This would be rare. The vacuum line to the EGR could be bad. Or the EGR valve could be sticking.
When the ECR does not work, you probably would not notice a problem. The EGR reduces the fresh air in the cylinders by adding exhaust gases. This reduces the amount of oxygen which allows the engine to make less oxides of nitrogen or NOX. It also will reduce soot perhaps, but by a minor amount.
The soot from the exhaust can mix at the EGR with oil from the intake air. Oil come from the turbo seals, a small amount which is normal, plus oil in the crank case vapours that go into the intake between the MAF and the turbo. This can result in heavy sticky or hard deposits. This is a problem that the industry has not really solved. The latest suly synthetic diesel engine oils are formulated to help prevent some of this.
I hope this helps, I am really guessing about what your are asking.
With the VW TDi engines, many owners are getting the settings in the ECU changed to reduce the amount of EGR, and some are also putting oil traps in the crankcase gas hoses. This reduces the manifold deposits.
97 VW Passat TDi diesel
posted by 208.24.179...
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