im working on a 96 impala ss, alil info before i start.

only mods are: t-56 swap, and cai.

codes that are present are for auto trans not being there.
and p0300.

problem started about 1 yr ago, friends car, one day just started to run rough. was brought to a shop and they threw everything possible at it. from what i can see, and owner remembers this is whats been done.

opti replaced 2x
opti harness replaced
pcm 2x
both bank pre cat ho2s
map sensor and connector
plugs and wires, plugs gapped to .50
exh man gaskets
injectors flow test and 2 replaced.
possible icm replaced. (owner cannot remember)

what i have done since i have receive the car.

found cylinder 4 dies once in closed loop.
i swapped injector #4 with injector from oposite bank for testing. (no change)
swapped ho2s from side to side. (no change)
removed ho2s to test for poss plugged cat. (no change)
checked grounds, and connections to sensors
cylinder 4 still has spark when goes dead.
checked injector connector for signal from pcm with noid light. (signal present)
took a snap shot using tech 2. have available if anyone can read .sur files

if i think or test anything else, i will post. any ideas?

 

Check the injector connector for yawning pins. Are the intake bolts tight? if not, its an "internal" vacuum leak. Other things are wiring harness with broken wire, or injector driver in ecm is taking a dump.

Check everything else first, Then replace pcm if nothing else. Also if the calibration wasn't changed for the t56, then the misfire monitor settings and thresholds will be wrong since rotating assembly mass is different from 6 speed to auto.

Chris

 

ok so i figured out the 96 ss i was working on. turns out that the 2 right side o2 sensor harnesses were swapped, so the front o2 was actually reading the rear and vise versa. the connectors are both the same, and they will reach either position and the wire colors are all the same too.