Will a V8 internal combustion engine still be able to run if one of the spark plug wires has been cut off.

Failing spark plugs can cause the car engine to misfire and thus affect its performance. A single spark plug that fails to ignite the fuel-air mixture can cause a halt in the running of the engine. It can result in incomplete combustion and damage to the catalytic converter of the car.

Yes, but as @Forever_Free wrote, it won’t run smoothly and it will waste fuel. And you’ll get dirty exhaust.

And you won’t pass emissions inspection.

It will run, you will notice a decrease in power ,plus a noticeable miss in that cylinder, but it will run.

Depends on the vehicle. Some will sense the misfire and either go into “limp mode” or shut down completely. Older ones will most certainly keep running. It’s known as “dragging a cylinder” I had a friend who had a Yamaha R1 motorcycle he got used. He rode it for the better part of a year, even regeared it for the kind of performance he wanted. It felt fine to him. He let someone else ride it who had one before, and they could tell. Turns out it was a bad plug wire. He had no idea.

Yes, it will continue to run, but you will likely have such a rough running engine you will find yourself pumping the gas to keep getting it past the missing spark. And it will probably cause issues further down the line in the exhaust manifold and system. This explains how an engine with a bad spark plug wire would operate. I’m equating a “bad” wire with a cut wire…same effect.

I think it does depend on the engine.
Having said that, in theory, it should run…

It will run but miss fires and decreased engine efficiency (gas mileage and acceleration).

<—Ex-automotive engineer
It will absolutely run. You might not even notice it However, if the vehicle is 2000 or later the OBD II diagnostics will turn on the Check Engine light and you will not be able to pass inspection.

But, the worst effect will be the combustible mixture of air and fuel passing into the catalytic converter and reacting there. The temperature will go up.- maybe to dangerous levels for the converter.
So…
If you have to make it run, I would disconnect the fuel injector and the spark plug. Then you are good to go. You will get a little more air into the converter but the closed loop fuel control has enough authority to bring the mixtures back to stoichiometry in the converter.
The check engine light will go on but it will drive quite nicely.

Thank you all for your responses.

@LuckyGuy If someone cut one of the Spark plug wires with a wire cutter and didn’t tell the car owner then would the car owner likely notice a decrease in acceleration power when he attempted to drive onto a freeway?

@gondwanalon The driver might notice a slight roughness at low speeds and part throttle, but the power drop would be unnoticeable under most conditions. For the vast majority of your driving you are not going to full throttle or demanding more than about 50% of the engine’s power output.
On a V8, losing one cylinder only drops max power and torque by ~12.5%. Rarely does the driver demand more than 30— 50%. Think about the last time you actually went wide open throttle. It was only for a second or two and you did it for fun rather than a true need.
If you were to unplug the matching fuel injector even your fuel economy would remain virtually unchanged.

With the fuel injector still operating, the biggest issue would be damage to the catalytic converter. It will get very hot. (During an emission test on a dyno I had one get so hot the interior carpeting began to smoke and melt.)

Yes. The engine will lack power and will use an excessive amount of gas. About 25% less power at all speeds and about 25% more gas used. (If the engine was a four or six, the miss and fuel consumption would be even more noticeable. But you asked about a V-8 and didn’t mention fuel emissions and OBD I or II, so I didn’t address those things.)
If a spark plug wire was cut, the driver might hear the spark jumping to a ground (engine block.)

I understand from the information above that driving a V8 engine car with one spark plug wire cut will be able to drive slow to moderate speed would not be a problem.

Here’s a situation that I’m thinking about:
The driver of the car with the V8 with the single cut spark plug wire is a young guy who likes to race other cars. Prior to the spark plug wire being cut he won a few races with other cars.

Am I wrong in thinking that the racing speed achieved when the V-8 engine has all spark plug wire intact will be substantially faster the when the car’s V8 engine has one spark plug wire cut?

Overall top speed may not be a problem but getting enough power to win a get-up-and-go race will be. I might be able to beat your V-8 with one dead cylinder with my little 2400 cc 4-banger running on all 4.

@kritiper Thanks. That’s makes sense.

The analogy that I’m thinking of is someone suffering with atrial fibrillation (AF) is similar to a car with one spark plug wire cut. In each case you can get around slowly OK, but you best not race anyone.

A heart beating in AF is 15 to 20% less efficient as a heart beating normally.

I trained for over a year to prepare for national canoe sprint competition last weekend. A couple weeks before the competition my heart suddenly for no apparent reason went into persistent AF. That added 10 seconds to my 500 meter time. I finished 5 seconds out of 3rd place. So frustrating. Reminds me of this quote:

“It’s an ache, a helplessness, an anger. One feels humiliated.”
-Harold W. Abrahams