I have been battling an ill tempered idle for some time and have replaced the plugs and wires with OEM (I changed the plugs and wires at 130,000). The burb has 150,000 on it and I have maintained it since 2008. This evening I thought I would see if there is any arching and I found that I can see a spark inside every coil pack. I also can see arching by the wire boots.

Is it normal to have a spark in the coil?

I thought that a coil is continuous and should not have a spark anywhere in it.

 

if its misfiring only at idle; check your fuel trim. if its adding at idle and not at 2500 rpm; you probably have an intake air leak. ever done the intake gaskets?

 

I am going to do that this weekend! I was told that my coil packs were all bad, so I replaced them along with plugs and wires. It has given the truck a smoother idle but it still has a noticeably rough idle. The old plugs had the high temperature/blistering on the ends. So my guess is that it is running lean. Thanks for the reply and I will update when done.