Date registered: Oct 2011
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D Jetronic Idle Air Valve
Trying to fix a no cold idle on a 71 W114 280CE with M110 and D Jetronic. Looking at all the great D Jetronic information on the site, the fault would appear to be with the thermal expansion activated idle aux air valve.
1. No problems starting
2. No idle when cold, but ok with throttle just a little open
3. Tick over fine one normal temp reached.
The valve when cold seems to be stuck open and supplying air around the flap valve - which is what I hough to be correct. I am expecting the valve to close when normal temp is reached so only air path is through the throttle flap valve
Checked by removing air pipe from the valve to the inlet manifold and blocking this up so there is no aux air supply, and engine idles perfectly when cold, and also compensates when auto is moved in to drive.
So should the valve be open when cold, and close when hot, and I am chasing the wrong fault?
The valve is deep down on the side of the engine under the manifold, and not easy to get to from either top or bottom, so hauling it out is going to be difficult, and I am loosing sleep trying to figure this out!