Hey guys,

Last night I was hard on the gas when VTEC engaged in 3rd gear and I heard a muffled pop (~6200 rpm) which sounded like a backfire through the intake side! The car vibrated when that happened but it didn't lose any power or trip any check engine lights.

The car drove fine after that and I engaged VTEC a few more times (ok, more than a few ) on the rest of the way home without any unusual noise.

The car is a stock 04 with a K&N intake only... has anyone else heard this noise before?

 

did you check under the hood yet? did you see anything, visually, when the "popped" sound occurs?

 

I checked and didn't see anything...

Now I get a weird rattling noise when in VTEC that sounds almost like a chipmunk

I think it's a loose heat shield. I can feel the vibrations in the floor pan. I should check the header heat shield as well as the cat. one.

 

check every possible places.

 

let us know if you find out what it was.

 

Were you making a turn when this happened.
I had a similar sound happen to me, but had no idea what it was.
I have an EMS and thought it might have been my boost load cut(cant rev passed 9 PSI).

 

um...I don't think the popping would have anything to do with heatshields...

backfires normally occur when there is to much gas or gas vapor that ignites either in the intake manifold or before the valve is closed...both would normally cause a lot of damage.

I'm sure that your "backfire" must have been something else/minor if you are not having any other problems now...

 

No problems since. I couldn't find anything loose or damaged.

My friend was in the car when it happened as well... it sounded exactly like a minor backfire through the intake side. A single (minor) backfire shouldn't damage anything... I just wanted to see if anyone else has heard this noise before.

I also noticed that all the rattles/squeaks etc are way more pronounced with the top up. So I think I'll just VTEC a lot more with the top down. haha.

 

is it a good thing or a bad to have the "pop" sound, guys?

 

Well it's not a good thing.

Unless it's your BOV