EGR help - wassis?

[Parrot of Doom]

I've been trying to help another member with very poor fuel consumption, and hes found that one of the vacuum lines to the EGR valve has been disconnected, and capped. He says that his mechanic did this, and the vacuum line is now flopping around the engine bay.

Its an OM606 turbo engine (3.0 TD as fitted to the W210)

I don't think this is helping matters. From his description, it sounds like the pipe in the picture on the left (the portrait orientated one) - which connects to what looks like a sensor, bolted to the firewall.

Please note that these are pictures from my engine bay, not his.

Now I'm guessing that its a sensor that tells the ECU when the EGR valve is open/closed, or the relative position? You can see the vacuum line heading up into the base of the device to a point just below one of the bolts that holds it in place.

I have no idea what the other device is.

Could somebody enlighten us as to the purpose of these two components, and how their failure/removal might adversely affect the running of the engine? I have a feeling that the ECU is getting all confused, and this could be why hes getting such poor fuel consumption - although thats a guess on my part. There are fuel leaks, but we're talking 20mpg here, which is frankly awful.

 

[television]

I am not good with diesels owing to the different condition in the way that they work, due to the higher air flow and no depression in the manifold at idle
http://www.detali.ru/cat/oem_mb2.as...GA=722.608&CT=M&cat=19T&SID=14&SGR=090&SGN=06
http://www.detali.ru/cat/oem_mb2.as...GA=722.608&CT=F&cat=45Q&SID=80&SGR=015&SGN=01

The EGR valve is a device that returns harm full exhaust gas back into the inlet manifold when the engine is running light, say cruising on motorway, as said before when stuck open causes rough idle

 

[Uncle Benz]

The item in the first picture is the MAP or Manifold Absolute Pressure sensor. The ecu uses this reading to monitor the pressure level in the inlet manifold. The second item is a control valve which opens the EGR valve with a vacuum, switched by an electrical signal from the ecu. This second item is common for causing loss of power after a reasonable length of journey. Car seems to get progressively slower.

 

[television]

I would like to say thank you Uncle benz for that.

 

[Parrot of Doom]

So its fair to say theres absolutely no viable reason for either to be disconnected?

Re-instating that vacuum pipe would result in either 1) no difference (due to another fault), or 2) a properly working car

Benz, do you know what effect the signal from the MAP has on the ECU? Would it affect fuelling, or the turbo?

 

[Parrot of Doom]

Hunting around, I found this useful page of piccies - it supports what Uncle Benz says about the control valve:

http://207.44.234.41/intake/IMG_8339.html

 

[television]

So its fair to say theres absolutely no viable reason for either to be disconnected?

Re-instating that vacuum pipe would result in either 1) no difference (due to another fault), or 2) a properly working car

Benz, do you know what effect the signal from the MAP has on the ECU? Would it affect fuelling, or the turbo?

People disconnect them when they are sticking as the spring becomes weak and they get coked up. they can never be successfully cleaned as the spring is weak

 

[Parrot of Doom]

ok its actually the control valve that has been capped - the sensor is still connected. I asked him to reconnect it. The mechanic said that it could improve fuel economy by disconnecting it, I'm not quite sure how tbh.

 

[television]

EGR stands for exhaust gas recirculation. Exhaust gas is routed back into the combustion chamber because the exhausted air is much hotter than the intake air, by sending these warmer gases into the combustion chamber the air/fuel mix does not have to as much work to heat up the combustion chamber, this enables the engine more efficiently from a cold start, reducing emissions at the same time.
The main reason for failure is down to where the valve is situated, the build up of sooty deposits eventually cause the valve to seat incorrectly in the closed position.

 

[Hibbo]

If the line to the MAP sensor is disconnected, then the ECU thinks that there is zero boost pressure, and so won't increase the fuelling as it should. This would result in a lack of power, and maybe having to have a heavier foot to make up for this could increase fuel consumption.

 

[eric242340]

If the line to the MAP sensor is disconnected, then the ECU thinks that there is zero boost pressure, and so won't increase the fuelling as it should. This would result in a lack of power, and maybe having to have a heavier foot to make up for this could increase fuel consumption.

Ive lost the thread here. To keep it simple : loose the EGR and close it down, only a problem with a cold engine. But, if the MAP sensor is disconnected - major problem. A loss of power and eating fuel would be a normal result. On the 126 range, welding the EGR welded shut actually improved the condition. I know this is not a 126, but you get my drift.

 

[chelsw6]

blanking plate

I have not done this myself, and i dont know if its all diesel cars, but they are ment to run better and get more miles to the gallon with out the egr valves connected, blanking plates are made for some cars and all you do with the vacuum pipe is put a ball bearing in it and cable tie the end, also its ment to be ok on the mot.

 

[Parrot of Doom]

Thanks chelsw6, but you can only do that mod on the non-turbo 606 engines.