Technical Can loose connection between a spark plug wire and the ignition coil cause intermittent ignition issues?

[nikolacvetanovski1996]

The ignition coil on my FIAT PUNTO EVO was replaced by a mechanic and it solved the issues with the intermittent loss of power and misfires that I’ve been having for the last two days. But while the mechanic was installing the new ignition coil he said that he barely managed to attach one of the spark plug wires to the ignition coil. I asked if the wires were bad and need to be replaced too, but he said that the wires are in excellent condition and that he managed to attach the spark plug wire to the ignition coil. All 4 spark plug wires were replaced a year ago (before 16.000 km were driven). Was the ignition coil really bad and was it the culprit for the issues that came up or maybe the wire had a loose connection and that caused the issues?
By the way all of the error codes were P0300
and P0304, indicating problems only with the 4th cylinder.
I’m suspecting that the old ignition coil was good and I replaced in vain. Am I wrong?

 

[bugsymike]

The ignition coil on my FIAT PUNTO EVO was replaced by a mechanic and it solved the issues with the intermittent loss of power and misfires that I’ve been having for the last two days. But while the mechanic was installing the new ignition coil he said that he barely managed to attach one of the spark plug wires to the ignition coil. I asked if the wires were bad and need to be replaced too, but he said that the wires are in excellent condition and that he managed to attach the spark plug wire to the ignition coil. All 4 spark plug wires were replaced a year ago (before 16.000 km were driven). Was the ignition coil really bad and was it the culprit for the issues that came up or maybe the wire had a loose connection and that caused the issues?
By the way all of the error codes were P0300
and P0304, indicating problems only with the 4th cylinder.
I’m suspecting that the old ignition coil was good and I replaced in vain. Am I wrong?

What can happen is if the wire is not making a good contact whether on a coil or a distributor cap HT connection the HT voltage can actually erode the plastic around the neck of the coil or the distributor cap etc.
A bit like a spark erosion machine in a tool shop using high voltage in an oil tank to shape a piece of metal.
However going back to your car , if the plug wire connection is poor then eventually it will cause the same problem again.
I have seen a distributor cap where the spring loaded carbon the transmits the HT volts to the rotor arm is missing, the car ran for some time but the spark was eating the inside of the cap away around that area.

 

[The Panda Nut]

Agreeing with Bugsymike. Ignition leads are cheap so change them. Any good ones you take off can be available for spares. Bad connections will cause bad running.

 

[nikolacvetanovski1996]

I have changed the ignition leads before 16.000 km. The new ignition coil was way more expensive, but the mechanic first told me to start with the ignition coil and the new one solved the problem. I was just confused when the mechanic told me that one of the cables was hard for attaching to the ignition coil, but he somehow managed to do that and after that he told me that the spark plug wires were good. According to what I described in this comment and in the entire post, is there a possibility that the new ignition coil did not fix the issue, but the reattaching of the spark plug wire? Could it have been loose? Could the old ignition coil be still good, so I don’t need to dispose it, but keep it instead?

 

[bugsymike]

I have changed the ignition leads before 16.000 km. The new ignition coil was way more expensive, but the mechanic first told me to start with the ignition coil and the new one solved the problem. I was just confused when the mechanic told me that one of the cables was hard for attaching to the ignition coil, but he somehow managed to do that and after that he told me that the spark plug wires were good. According to what I described in this comment and in the entire post, is there a possibility that the new ignition coil did not fix the issue, but the reattaching of the spark plug wire? Could it have been loose? Could the old ignition coil be still good, so I don’t need to dispose it, but keep it instead?

If you think the old coil is good, examine it around the area the ignition lead fits and if you can see no damage refit to car and try it.
However I would advise a careful inspection in the area I mentioned for tracking and spark damage, it can look like a crack but is caused by the spark taking the easy route especially if damp or dirty rather than firing the spark plug.
The metal part of the ignition lead needs to sit as deep as possible inside the neck of the coil so no chance of as poor connection and must be secure.
On a slightly different point, one of my sisters had a Honda, bought new from the dealers and always serviced by them, she mentioned that after reporting an intermittent misfire she had new expensive genuine coils fitted on several occasions.
I advised her to have new spark plugs fitted even though the Dealer said they were not needed at that mileage, she insisted on my advice and it cured the problem.
The reason being as the plugs wear the gap gets wider and the plugs need a higher voltage from the coil to spark the plugs.
Another point that makes matters worse is modern regulations mean ignition systems have greater radio suppression resisters fitted , so you have suppressed HT leads made of carbon string which breaks easily internally so not visible, resister spark plugs and in some cases resisters in the rotor arm where used.
All these make the voltage higher, so like water more likely to take the easy path/route and short out.
As an apprentice in the 1960s cars ran happily using 6000 volts to fire the spark plugs where as nowadays it is more likely to be between 20,000 and 100,000 volts in some cases.