My 2000SS has a slight backfire right after
cold starting. It has a Comp Cam 212/218 .521/.527
with an 115 deg LSA and 3 degree advance.
Other mods ar bolt ons and stage 1 ported heads
as well as shorty headers. I also have E. Wright
custom programming for this set-up.
What are typical causes for this - again it disappears when half warmed up or fully warmed up.
Thanks,
Gert

 

My stock-internals 2001 LS1 does this also, the PCM runs the engine rich until it gets warmed up.

 

I also agree. I think the computer tuning has something to do with it. You're talking about a slight exhaust backfire, right?

 

Yes, I am just talking about a slight backfire,
an occassional "poppop" sound, about three to four times. The idle is probably richer than stock. I could reduce this a bit by going to
-5% with my MAF for this range.

Gert