Is there a wire on lawnmowers that run to exaust to keep engine from back-firing when shutting off

Have the exaust system checked pluged up cat will act like that
The exaust cant get out so thats when it dies once the exaust bleads off it will start again

I looked at info for the v6. If you have the spider fuel system, I'd check that first. That system is noted for problems. Use a gage and check proper fuel pressure.
Check and clean anything that has to do with idle air system, see if it helps?
I don't like the sound of that white smoke, you may have coolant getting into the combustion chamber.
How long since a tune-up? Any applicable trouble codes?

Should be your catalytic converter is plugged up.
should be replaced

You've got TWO catalytic converters.Did you replace them both? Are you running 91 octane or better? don-ohio

firing order 153624 make sure valves on no1 cylinder are closed with cams pointing upwards then the rotor arm points to this plug lead and away you go ,This cylinder is no1 and then swop the others to follow the firing order ,once running either check with a timing light or swing distributor till engine runs faster then back it up a bit till it just starts to slow and should be right if it pinks the back it back a bit more till it stops pinking

FIRING ORDERS

Before carrying out extensive tests to isolate poor running problems, check connections of spark plug wires. This is especially important if plugs, wires, distributor, etc., have been disturbed recently for service. Obviously, this is not applicable to the wireless 4.7L engine.

NOTE To avoid problems, remove and tag the spark plug wires one at a time to ease reinstallation.
For vehicles with an extensive service history, keep in mind that the distributor could have been removed previously and rewired. The resultant wiring would hold the correct firing order, but could change the relative placement of the plug towers in relation to the engine. For this reason, it is very important that you label all wires before disconnecting any of them. Also, before removal, compare the current wiring with the accompanying illustrations. If the current wiring does not match, make notes in your book to reflect how your engine is wired.

Fig. 2.5L Engine Firing Order: 1-3-4-2 Distributor Rotation: Clockwise

Fig. 3.9L Engine Firing Order: 1-6-5-4-3-2 Distributor Rotation: Clockwise

Fig. 5.2L and 5.9L Engines Firing Order: 1-8-4-3-6-5-7-2 Distributor rotation: Clockwise

Fig. 4.7L Engine Firing Order: 1-8-4-3-6-5-7-2 Distributorless Ignition

Fig. 8.0L Engine Firing Order: 1-10-9-4-3-6-5-8-7-2- Distributorless Ignition
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It sounds like you need to inspect the wiring harness and look for broken wires and any wires that are hanging they may not be connected, the black exhaust is caused by a choke plate that is not opening on the carb the electric choke is not getting any voltage through the wire or the choke plate is out of adjustment it should be wide open after 5 minutes of running, check the fuses to be sure there is no blown fuses and check the wire that goes to the carb. to ensure it has 12 volts.

No, the o2 sensor and coil pack are not the same. The o2, or oxygen sensor, is mounted in the engine exhaust and produces a signal that the cars engine computer uses to calculate how much fuel to give to the engine. The coil pack is an ignition system part, it is what provides the voltage to make the spark plugs fire.

0300 is a mis fire. Explains the fried wire. Were all the plugs changed?? If not, definately change the one on the fried wire. Possible burnt cylinder. Does it fire/start right away cold?? If not, it could be the coil. Start by checking spark in all your wires and plugs. This will isolate your issue hopefully.

As long as you have fuel pressure and good fire on the ignition system. When you try and give it the gass to rev it up do you hear a wooshing sound from the exaust at all, kind of like it is plugged up. If so replace the catylitic converter, it is plugged up. The exaust manifold will get red hot if you run it for too long also. If it is not plugged up, then I would spend the money and pull the valve cover and see if you have a rounded cam lobe on one of the intake or exaust valves. This keeps the gases from getting out of the motor and holds it back. Sometimes it will also backfire thru the carburator when trying to accelerate the motor. Good luck, RAC