Zafira A EGR Valve Problem

[wanleg]

Hi,

Vauxhall Zafira A 2004 2.0DTi Y20DTH engine.

Anyone know if the EGR valves are electronic on this engine i.e. what opens and closes them? Mine is same as attached pic and does have a multiplug going into it.

View media item 29826
Do they open gradually as engine revs increase or are they just either fully open or fully closed?

I'm just trying to understand how these work and why they fail so regular....in the 4 years I've had the car I've had one replaced under warranty, one replaced I had to pay for, the last one cleaned (which lasted about 6-7 months) and now have the same problem again....my independant garage has cleaned again but it still hasn't sorted the problem....I fear yet another replacement coming.

Cheers

 

[Jimmyjaffa]

As the name suggests 'Exhaust gas recirculation valves', first introduced in 1972, are used to feed back a portion of the exhaust gases emitted by the car engine, back to the combustion chamber. The addition of these volume of gases reduces the quantity of oxygen available for combustion. Also, the addition of exhaust gases made to the air-fuel mixture, increases its specific heat capacity.


Due to both these factors, the adiabatic flame temperature of combustion. That is, the dearth in oxygen and increase in heat capacity, lead to the combustion of a gases at lower temperature. This effectively reduces the amount of mono nitrogen oxide gases created and released. Generally 5% to 15% of the exhaust gases are fed back in spark ignited engines. In diesel engines, the exhaust gases are cooled before they are fed back to the engine.


The efficiency of the engine does get reduced but there is a switching mechanism in place to take care of that. When the engine has a high RPM demand (Wide Open Throttle Conditions) and is in full acceleration mode, the EGR valve action is stopped and exhaust gases are no longer fed back to the engine. This ensures that the engine efficiency is not compromised when the RPM demands are high. It is also turned off when the engine is idling as it can destabilize the engine. Only in the region of mid acceleration, where the engine is between the two extreme conditions of full throttle and idle, does the EGR valve come into play. In modern cars, the action of the EGR valve is controlled by electronic engine controls mechanism.




they always go because of the build up of carbon and crap caused by the mist of oil sent through the egr via the turbo(mainly diesels). oil and heat from the egr equals gooey carbon and when built up makes the valve stick. normally a good clean will solve it.

 

[Belle427]

they usually have a small motor to drive the valve, id guess this burns out when trying to constantly drive it open when its coked up

 

[wanleg]

Thanks for both the replies. Car is back into garage next week for service so am getting them to look at EGR valve again. Seems to be an achilles heal on these cars....car gets 95% of its used around town at 30 mph so maybe this is actually exasperating the situation....if it did longer runs with more throttle then maybe the EGR would coke up as quickly.

 

[Belle427]

i clean mine every 6 months as part of its maintenance now

 

[Jimmyjaffa]

i would think about bypassing it myself.

 

[wanleg]

From what I read you cant on the diesels but on the petrol engines Vauxhall do a blanking plate....the ECU can then be programmed to forget about the EGR.

 

[Stivino]

Here's a wee You tube video that shows how to isolate it.
http://tinyurl.com/4e5wfdd