If the engine shuts down, you are loosing ignition power. It is possible it is just power to the ignition coils. You may be able to determine this from your dash. Different things light up if you are only on accessory or on full ignition.
The downshift causing this is most likely causing movement of a wire or connector, breaking the connection or shorting it out.
-
Start with the dash observation. If it is not a full ignition shut down, inspect and reseat spark coil wiring.
+
Start with the dash observation. If it is not a full ignition shut down, inspect and reseat spark coil wiring and connectors.
If it is a full ignition shutdown, look for loose fuses or intermittent/loose relays, or damaged wiring.
If the engine shuts down, you are loosing ignition power. It is possible it is just power to the ignition coils. You may be able to determine this from your dash. Different things light up if you are only on accessory or on full ignition.
The downshift causing this is most likely causing movement of a wire or connector, breaking the connection or shorting it out.
Start with the dash observation. If it is not a full ignition shut down, inspect and reseat spark coil wiring.
If it is a full ignition shutdown, look for loose fuses or intermittent/loose relays, or damaged wiring.