Ignition problem
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Junior User
Joined: Aug 2003
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Ignition problem
86 F150 4.9
Feels like the engine misses while accelerating. So I am looking at the plug wires while the engine is under a slight load and I see a spark jumping from the plug wire to ground. It looks cool but I don't think it is supposed to do that.
Would the silicone grease cause this? They are new plug wires and relatively new plugs. Its acted like this for about 2 months. Just seemed to lose power on the highway when trying to pass.
Feels like the engine misses while accelerating. So I am looking at the plug wires while the engine is under a slight load and I see a spark jumping from the plug wire to ground. It looks cool but I don't think it is supposed to do that.
Would the silicone grease cause this? They are new plug wires and relatively new plugs. Its acted like this for about 2 months. Just seemed to lose power on the highway when trying to pass.
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
If you see arcing, either the plugs are gapped to widely or the new wires and bad. The spark will find the easiest path to ground and that should be the spark plug gap if all is working well. It's not the silicone grease, that should help if anything.
And yes, that is the cause of the miss and power loss.
Could be the wrong plugs too.
And yes, that is the cause of the miss and power loss.
Could be the wrong plugs too.
Thread Starter
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Junior User
Joined: Aug 2003
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I now have tried a new set of wires. Still hear it clicking (when spark jumps), still missing.
I did notice that this happens mostly when warmed up.
Spark plug gap on all is .044 .
Maybe if I put the wrong grease on wires???? but it worked fine for year and a half and now its missing? I'll inspect componants for cracks ??
I did notice that this happens mostly when warmed up.
Spark plug gap on all is .044 .
Maybe if I put the wrong grease on wires???? but it worked fine for year and a half and now its missing? I'll inspect componants for cracks ??
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
I'm going to suggest that you have resistor plugs of a type that uses a gap inside, and the gap has burned itself open wider than it's design. Try a new set of Autolites as specified for your truck. The problem, that causes the arcing is from a very high resistance. Try putting an ohmmeter on the center electrode and the contact at the top. I'm betting that you have an extremely high reading.
