Does anyone know why my car’s RPM drops from 1200 to 500 or lower and then stalls when I start it cold? It shows a power error. I notice the spark plugs have slightly different numbers and the exhaust smells very rich. 
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have you done diagnostics ? Does it start and turn off or only turning by starter?
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Cold start, engine starts then from variabel moter rotation between 500 and 1500 up and down… diverse… rotation then drops instantly below 500 and shuts down. Trouble starting 2th time… fumes smell rich of gas… spark voltage is not equal to all pluggs . When shut down power error shows on dash.
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The Ford garage checked everything but didn’t find any errors. They looked at the power, spark plugs, and emissions. The carburetor and timing were fine. When I told them my OBDII software showed the voltage fluctuating and jumping around, they didn’t say much. I’d like to know what the normal spark voltage should be.
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Check the IACV It might be dirty or malfunctioning, which can cause the RPM to drop and the engine to stall when cold.
Inspect the Fuel System: A rich exhaust smell and fluctuating spark plug numbers could indicate a problem with the fuel injectors or fuel pressure, leading to a rich fuel mixture and stalling.