1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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17,293 Posts
Is the cold idle speed OK? The IAC should catch a stall before it occurs, is it responsive and varying the idle speed as an engine load (like the A/C compressor) comes in and out?
Maybe check the plug tip color right after the first cold stall. Black could indicate rich or misfiring plugs. Light could indicate normal or lean. Secondary ignition health (including rotor, cap, wire and the correct "Champion" plugs) is important as firing voltage requirements are much higher when cold.
There are some DRB II IAC tests to see if the PCM and IAC can track a selected idle speed on the DRB successfully.
There was a TSB on carbon build-up behind the intake valves that could result in a cold, lean condition. Much of the fuel from the injectors would spray into the carbon instead of going into the cylinders. It would soak up into the carbon deposits like a sponge. In cold open loop, the O2 sensors won't yet compensate for the missing fuel and as the carbon saturates with liquid fuel, then the problem goes away.
We use a laproscope down the throttle body to view the back of the valves. Modern quality fuel with cleaners and solvents should keep carbon build-up to a minimum or you can try a bottle of Techron in the tank for a couple of tankfuls.
Maybe check the plug tip color right after the first cold stall. Black could indicate rich or misfiring plugs. Light could indicate normal or lean. Secondary ignition health (including rotor, cap, wire and the correct "Champion" plugs) is important as firing voltage requirements are much higher when cold.
There are some DRB II IAC tests to see if the PCM and IAC can track a selected idle speed on the DRB successfully.
There was a TSB on carbon build-up behind the intake valves that could result in a cold, lean condition. Much of the fuel from the injectors would spray into the carbon instead of going into the cylinders. It would soak up into the carbon deposits like a sponge. In cold open loop, the O2 sensors won't yet compensate for the missing fuel and as the carbon saturates with liquid fuel, then the problem goes away.
We use a laproscope down the throttle body to view the back of the valves. Modern quality fuel with cleaners and solvents should keep carbon build-up to a minimum or you can try a bottle of Techron in the tank for a couple of tankfuls.
