1989gta

i have a problem
here's what happens
-you turn the key and vehicle will not fire. you unplug the o2 and it fires and drives and what not.
-when the engine warms up and goes to use the o2 it pulls a code 13 and starts running crappy and back fires and surges. on the freeway speeds only if you are city driving its fine stopping and starting.

what i did was replaced the O2 still no luck
it also has new head gaskets
wires plugs cap and rotor.
-fuel psi is good it's getting spark
this is a non mass air vehicle
i tested the map sensor and coolant temp sensor so i know warm up is okay.
i would like to not have to buy diacom software or have a shop hook up a scan tool.

any ideas would be great.
thanks guys

kevin 2.8

get the timing checked
if that doesnt do it, get the cat cut off and see if its clogged

1989gta

yeah i checked the timing it's almost perfect.

it only cuts out really i guess at hwy speeds at 1/4 throttle
when your in town, stop and go it's fine.

so a plugged cat that would effect performance all the time right?

would that also cause the engine to run hotter than normal due to increased back pressure?