If you didn't replace one spark plug wire at a time you may have mixed up the firing order.
Check firing order Two of the plug wires are crossed.
Was the truck running OK before the plugs were changed?If ok before the plugs were changed then I would recheck the plug gap & check the plug wires. It is easy to damage the carbon fiber inside the wires. If they are old say around 40.000 miles I would change them. If truck was running rough before plugs were changed I would look at timing & vaccuum. Also cap & rotor. The converter can be a problem with rough engine perform. Check for bad gas.
Foaming often indicates that the fluid level is too high. Maybe you overfilled the oil? Rough running could be many things. If you haven't changed plugs and plug wires lately, that could be a good place to start. FriPilot
Check spark plugs and wires Do a compression test
You should check to make sure that the electric fan is working.
Spark plug wires? Coil pack? Dirty injector? Spark plug wires? Coil pack? Dirty injector? Spark plug wires? Coil pack? Dirty injector?
When you experience a problem such as rough running when weather is damp or when they show any signs of cracking or damage.
Run a compression test.
check ur pluges and wires but also check ur starter
Your 1991 Cougar might be running rough because it needs to be serviced. Try changing the spark plugs, spark plug wires, and checking for water in the fuel tank. You might also have an issue with fuel injectors that are clogged.
i changed plugs wires throttle p sensor an checked fuel
Is it running rough? I am wiling to bet you need to replace the plugs/wires. The roughness you experience is the sparking or arching with old plugs/wires. They cost about $45. Use a light coating of bulb grease on the ends of the the new wires, and replace them in the right order.