CaptainDirtymax

hey guys, looking for some ideas as to what might be causing me issues with my '93 Z28.

little info on the car:
-1993 Z28
-LT1, 4L60 trans
-bone stock
-193k miles

the car runs perfect when it's cold. once it warms up though, the engine develops a low rpm miss. more specifically anything below 2000rpm. and it's running pig rich. i've been getting on average 8-9mpg in town. on the highway it's much better, around 21-23mpg (3.23 gears with an auto).

it has brand new plugs, wires, fuel pump and filter, 8 injectors, head gaskets and both O2 sensors. it does NOT throw any codes either. it's still on the factory Opti, but i've already checked it by putting it in my buddies car and his ran perfect with it.

any ideas???

mguidry629

iTrader: (6)

Some O2 sensors cause the ecm to read rich, but then the ecm would lean out the mixture and actually run lean, so nevermind. I don't know what else would cause it to run rich except for the tune and/or the O2s. What kind/size of injectors? What brand O2s? What brand/size plug wires? If you went with bigger injectors or the fuel pressure is higher, then it would run rich.

Did you try the ICM? I've heard ppl have problems with those when they get warm.

I'm sure some of the more experienced folks will chime in soon, but there's some suggestions to get you started.

chevycamarorules

iTrader: (5)

mine was the 02 sensor on the right side but it had a code i think 64-or 63
it might be the water pump temp sensor its cheap like $10 or swap your friends
make sure theres no air in the system after swap

CaptainDirtymax

factory replacement injectors, same for O2 sensors. everything was factory replacement parts.

another thing, before i got the passenger side O2 sensor swapped, i ran the car for about a month with the sensor unplugged (which helped a little with fuel economy), but it wouldn't throw a code until i had run it over 2000rpm for a solid minute. in town it wouldn't ever throw a code.

CaptainDirtymax

ok, so both sensors have been replaced. car runs better, but i still have the miss. it's definitely from the drivers bank though. i've been able to hear a loud clicking on the drivers side, and i didn't think anything of it. i thought it was an exhaust leak, but i decided to pinpoint it yesterday and it's coming from the valve cover.

could a lifter have gone flat and be causing the **** poor fuel economy and miss fire???