Hey, just wondering if you got your miss fixed?

 

I just went through this misfire extravaganza and was losing my marbles over it, changed the plugs, checked electrodes, coil... everything was good... but still the bugger stuttered and sound like crap. I gave in and took it to a pal of mine at a shop, it was the IAC valve - $100... so before you go through changing all your coils, fuel injectors etc. It might be a dirty IAC valve or just replace it all together... phew...

 

Might be a dumb question, but I'm curious... How do I know when I have a misfire? My cars a 5.4L V8. Thanks for the help

 

You'll know. No power really shaky wired sounds in lamens terms. Hard to explain. Here's an idea. Unplug one of your injectors, and start your truck don't let it run for too long but you'll see what I mean by weird noises.

 

Ok thanks, because like at around 35-40 mph there's a thump that I hear and I'm nervous about it

 

Where does it sound like its coming from? Could be trans or rear end. A motor is all rotating parts so it'll be a repetitive thump, if that's your concern. Trans might have a hard shift or maybe bad mount or rear end might just need greased up.

 

I can compare it to the hard shift

 

When you get to the speed that feels like a misfire cancel the O/D and see if it goes away or not. Maybe you can isolate where the noise is coming from.