450SLC:fuel injection timing sensor???

Hi Guys, I seem to be having an intermittent problem with my '73 450SLC. From time to time, the engine will stuble badly, but it will only last for a few seconds then the problem goes away as quickly
as it strated. I've ruled out an ignition problem, so I think the problem may be in the fuel injection system.
I do not have a manual that covers the engine. There must be a sensor that tells the injection system the postion of the crabkshaft. I sure can't find it! Sure would appreciate some help.
Steve
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Your EFI injection timing is controlled by the trigger points in the base of the distributor. Highly unlikely that they are your problem. There are 4 sets of points in the group. They send a signal to the ECU behind the glovebox. Each triggers a pair of injectors. The injectors are paired as follows: 1 + 5, 2 + 7, 3 + 6, 4 +8. The cylinders are 1-4 on the pass side, 5-6 on the drivers side, on a US LHD car...
The usual sign of bad trigger points is oil getting on 1 set and you lose 2 cylinders.
For an intermittant stumble on a take-off from idle, I would highly suspect the EGR valve. Do you have one? It will be on the top of the drivers side exhaust manifold. It is vacuum controlled thru a transducer that gets water in it. I would disconnect both vacuum hoses going to the EGR valve and plug both hoses. Drive it for a while and see if it corrects the stumble.

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