Per ardua ad cineris.
Join Date: Apr 2013
Location: Somerset UK
Vehicle: SLK230 '99 R170
Other Toys: Clio Williams
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The coils are relatively inert high power items, and so would not be affected by a power pulse when you connect the battery. In fact, a coil is normally used to control an inrush, to define a soft-start (in non-electronic designs) so is really safe.
But the support circuitry (effectively Capacitive Discharge Ignition) might just be able to suffer. But the normal failure mode for these is to fail, not to become intermittent. Again, it is power circuitry, so robust (and should be supported by robust design).
Dodgy connections (and broken wire harnesses) will make intermittent operation; pulling the cables might help this show up clearly. But all of these would run the same for
And some items (like low pressure fuel rail) will cause bad operation, even at tickover, and worse when throttle is applied. (Good option as described)
Leaking air would affect tickover, but as more throttle is applied, so the effect of leaking air will decrease. (Not applicable in this case.)
You could check the plugs to see what colour they are running at; at tickover, the plugs should be black to beige. When you increase the throttle, running under no load, they should go to beige. If they come out wet with fuel, then the plug and coil are not igniting (properly), if at all.
If you run the engine for a short while, and then whip out the plugs, you can confirm which plugs are running, and which are just getting warm from the compression of the cylinder.
However, if the fuel system is the problem, rather than the ignition system, then the plugs will all be dry, the plug colour will be light beige (since it's running lean) and they will all be the same temperature.