84Stanger302

Got an 86 gt a few months ago. efi stock intake and fuel setup, long tubes, catless x pipe, and a pypes cat back. been having an issue with rough idling on cold starts. when i first start it it will run at about 1800rpm then slowly come down to about 800 or so, after a while it is like someone hits a switch and it will go down to about 600 and run rough and somtimes pulse up and down. kind of confused on this one. BTW i replaced the intake manifold gaskets and made sure all my vaccum lines were connected and not leaking. it ran way better but still has the small idle issue.

any help would be great!
thanks
jeff

AdderMk2

when was the last time the O2 sensors were replaced?