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Thread: 1.7 EGR operation

  
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    1.7 EGR operation

    I have been given an 98 Astra 1.7td estate. Its been neglected a little but has come up fine after a little T cut and wax and makes a superb run about. With only 55k on it, it has years left yet, so is worth some effort. I found this forum while searching the net and if you guys can't help then I doubt I will find the info anywhere else.

    Problem. I have an intermitant EGR fault with the dash light coming on / off around 50 / 60 mph. Cleaned EGR valve, and its the same. Checked pipework fine. Cleaned electrical connex to gizmo. Still the same. Many hours searching has brought up lots of speculation and nonsense, but little actual fact.
    Can anyone here help please?

    Stuff I know for sure.

    1 - There is a spring loaded valve (EGR) that opens or closes port, between inlet and outlet. Spring operates ok, if finger placed over inlet when compressed, then it holds compression until finger is released, indicating diaphram inside is ok.

    2 - A pipe goes from EGR valve inlet to an electrical unit with two wires connected.

    3 - Another pipe goes from electrical switch to what appears to be a pump at the end of the cam. (RHS of head). Pipe is fitted to a spigot with a pinhole sized hole through to pump interior.

    4 - All pipes are in good condition.

    Questions.

    1 - What is the sequence of operation with these three units. When do they operate and why ? ( I know what the EGR valve does and why. What I don't know is just when does it operate, what decides to open or close it and why )

    2 - What is the function of the electrical unit? Is it a solenoid that allows vacuum / pressure control to the EGR or is it a pressure switch that measures vacuum and indicates low or failed vacuum? Where is it controlled from or where does it go to?

    2 - Is the pump, actually a vacuum pump? If so how does it work ? There are two sliding plastic blocks / seals in the rotor. How critical are these?

    3 - If the pump rotor is removed, the shaft can be seen to be hollow. Does oil pass down through this ? If so, won't it block the micro bore outlet spigot? If not, how is the pump lubricated? I have a small quantity of oil in the pump, (teaspoon) which may have blocked this outlet.

    4 - When the light is on, I understand the ECU is in 'safety' or 'get you home mode'. Can you confirm this is simply an rpm limit? I read its 2500 rpm. Others say its more complex than that.

    Please, no speculation or guess's, no 'my mate says' stories, I've read plenty of that. Just definite facts. Please only answer if you do actually know how it works!
    Big thanks for your time and help !

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    No one ? Someone on these forums must know surely?

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