[karlb65]

Hi all,

My 93 Nissan Sentra XE started running rough. I replaced the fuel filter, plug wires, and put new belts on it. Then it ran like a dream...for a few days. I didn't drive it for a couple days and then today I start it and it is running smooth as silk. I did the spark plug wire test where I removed the wires from each plug to see if it had any effect on the engine. When running rough it's the third cylinder that removing the wire has no effect on. When running smooth of course I take the wire off and the car misses. Any reason why it might be so inconsistent?

 

[sonicgundam]

you might have carbon tracking on the cap, causing a misfire, or you may have damaged the third wire or plug when installing.

 

[karlb65]

To Sonic

Would the things you describe cause the car to run super at times and not at others? I switched out the third plug with the first and the third cylinder still didn't fire, so I assumed it wasn't the plug itself.

Thanks for your suggestions!

 

[RJR99SS]

try spraying down that wire with water and see if it causes the miss.

 

[sonicgundam]

try spraying down that wire with water and see if it causes the miss.

its already missing often. it's a new wire, so i'd doubt its got an issue.

he's already identified that its an issue with the third cylinder. check the distributor cap for carbon tracking, seeing as its not the plug.

 

[karlb65]

Sonic,

I am getting a new distributor cap, so I will let you know if that is the culprit. I do remember a few days back that when I checked it the contacts underneath had white corrosion on the contacts. I'm assuming that's what you mean by carbon tracking.

Thanks!

 

[Centurion]

That white corrosion is unavoidable and quite normal. Another test is to look at it (Iggy wires and related) in the pitch black and look for arching. My car was running seemingly perfectly but I noticed some jumping between the wires, so i replaced them.

 

[sonicgundam]

Sonic,

I am getting a new distributor cap, so I will let you know if that is the culprit. I do remember a few days back that when I checked it the contacts underneath had white corrosion on the contacts. I'm assuming that's what you mean by carbon tracking.

Thanks!

that white buildup isn't carbon tracking, but it will still cause there to be no spark.

carbon tracking literally looks like a line drawn with a pencil, and it causes the electrical energy to move along the tracking rather than through the wire, basically shorting it out.