not exactly sure how to describe this...

you can hear it every time it makes the sound. it stops for a second then starts up again. anyone have any idea what i should be looking at?

full non-seq
stock twins
intake
blitz smic
power fc
stock fuel
stock cat
omp delete running pre-mix (not sure if thats relevant)

 

i watched your vid a few times...sounds like a timing issue by the way it idles or even too rich of at idle. what's your tune look like? fuel and timing maps? do you have a wideband to confirm its running rich?

 

Mine acts somewhat similar but there isn't a thud. It is more of a misfire at idle which for my port, is to be expected. I'm not very good at diagnosing these types of things but could it be a late burn? It sounds like it's trying to backfire at idle.

 

At first I think about a subwoofer XD


Idles seems not to be affected from this thumping.

Check injectors (especially primary) for leaking or bad spray pattern/wrong fuel quantity


remove Cat and see if something inside is moving (it's stupid but it's really fast to check)



Btw knock sensor say something? What about detonation?

Mine with a primary injectors dead can't idle well...but when idling make a similar noise becouse it' to lean....

Obviously my idle is really rough becouse only 1 of the primary have issues

 

Rod knock.

 

lol check your blinker fluid level too.

 

look at the wideband if you can , and check if there is any fluctuation in the AFRs as it thumps .

 

My car sounds like that when i first start it again, after its been driven for awhile/fully up to temp,
then has been shut off; left to heat soak and started again.
It clears up when it gets fresh cool air into the intakes etc..that's what mine does anyway and i don't worry about it.

 

Since I can't see anything. Unplug air pump. Easy and fast. Just to eliminate that.

 

Air pump has been deleted

 

Mine does this to a lesser (quieter) degree when its started up from dead cold.

I am pretty sure that it is slightly rich and there is some fuel that makes it into the hot exhaust manifold and ignites in there, periodically, giving that noise.

It hasnt bothered the car and it does go away once it fully warms up. My injectors were all cleaned and tested a while back, and I dont think they are a cause. I think its just startup richness.