How subtle can a misfire be?

[nelliott500]

Title says it all, really. I know the warranty on COPs has been extended to 100k miles for these cars, but I don't want to have the dealer check it and have to pay because they don't find anything.

Can a misfire be very subtle? I noticed on a cold start that the car has a slight shake. It's very light, but noticeable until it warms up and the idle drops.

I don't notice any issues while driving it though.

 

[Rich88LSC]

That very well can be weak coils. I had a couple getting weak and honestly didn't notice. The car was in for just an oil change and when I picked it up they said they changed some COPs.

 

[joegr]

A misfire can be minor and non-obvious. However, I wouldn't go in for just a slight shake at idle. That could come from a lot of things other than a misfire. For a misfire, you need to have issues while driving.

As a single example, I have an 06 and an 04, both V8s. The 06 idles very smoothly. The 04 has a slight shake at idle and has since new. I have been through misfires with the 04. I couldn't really tell any difference at idle, but I could tell under mild acceleration.

 

[nelliott500]

Thanks, joe. I'll just let it go for now. I've got plenty of miles left in the warranty so I'll hold off until it gets worse (if it is a misfire).

 

[BlackLS06]

A misfire can be minor and non-obvious. However, I wouldn't go in for just a slight shake at idle. That could come from a lot of things other than a misfire. For a misfire, you need to have issues while driving.

As a single example, I have an 06 and an 04, both V8s. The 06 idles very smoothly. The 04 has a slight shake at idle and has since new. I have been through misfires with the 04. I couldn't really tell any difference at idle, but I could tell under mild acceleration.

And if you get an intermittent rough idle....then you most likely have a misfire on cylinder # 8.

 

[jmtiseo]

To throw in my experience, I have the same year and model as yours and I also experience a little sorta rumble at idle at first start up. Haven't noticed it when it's all warmed up. When you have a misfire, you will probably most certainly know, especially when the motor is under a load.