Coil question

[Stayathomedad]

I have an 05 trailblazer ext with the 4.2. Is it possible that a coil is starting to go bad but works sometime, or is it all or nothing? I replaced plugs about a month ago, the right ones, because of a misfire on the wrong plugs. Now another misfire on 2 , I can't remember what the first misfire was, but I did notice that the coil looked a little different. It ran fine until now when the light can on, I was sitting and idling and noticed it.
Any thoughts or info
Thanks

 

[RayVoy]

These coils do seem to have a high failure rate . You' ll find a lot of suggestions (on this site) to swap the suspect coil (#2 in your case) with one of the other coils, to see if the fault code follows the coil.

I had an '05 for a number of years and, like you, had a few mis-fires. In my case, it was always the high voltage boot that had failed. I changed the boots and never actually had to change a coil.

 

[Stayathomedad]

Thanks for the thought, how did you test, find out that the boot is bad?

 

[RayVoy]

Just looking at it, there was a burned carbon path on the inside. BTW, the boots are available from the dealer, don't recall the price, but it was very reasonable (compared to a coil).

 

[Gevans17]

I have an 05 trailblazer ext with the 4.2. Is it possible that a coil is starting to go bad but works sometime, or is it all or nothing? I replaced plugs about a month ago, the right ones, because of a misfire on the wrong plugs. Now another misfire on 2 , I can't remember what the first misfire was, but I did notice that the coil looked a little different. It ran fine until now when the light can on, I was sitting and idling and noticed it.
Any thoughts or info
Thanks

BWD - Water Intrusion and Premature Coil Failure (

OEM TB hood seals are crap and allow water to run off the windshield and drip on top of the engine. Usually collects in/around sparkplug wells 4/5

 

[Stayathomedad]

I have heard about the seals. My misfire was on 2, towards the front of the motor. The car has 110k and are probably originals. Since then, no misfires. Driving my mind crazy.