1986 Firebird 2.8 AUTO 2.77gears

alright this is my major issue.. the gas mileage is very much a part of the problem. but my idle and acceleration is very bad

when i start the engine in the morning or after it cools it runs horrible. idle is very lopey(unstable) if i put it in gear the engine almost stalls at about 500rpm but raises to 650-750 after acouple seconds.
When i rev the engine to 3k rpms it sound real good but at 2k or lower its not soo good.

if i put it into gear and try to take off it hesitates for a second then accelerates but its pretty rough.. it does the same thing in park.

once warmed up the hesitation is almost gone but the engine is still not smooth and the idle is lopey... mileage is about 13mpg.

vacuum is 13 in park, 10 in drive with no leaks anywhere


if anyone knows of a sensor that i've not replaced that may be the problem or something i've over looked please let me know



i've replaced

Timing Chain
Manifold gaskets
Spark Plugs
Plug Wires
Ignition Rotor
Distributor Cap
PCV Valve
Water Pump
Alternator
Battery
MAF sensor
Fuel Filter
Rebuilt Transmission
Wheel Bearings
Vacuum lines
USED Rear end(good)
USED FWD Injectors
USED 92 Camaro Coil
USED TPS
USED Ignition Module
USED Fuel Pressure Regulator

i've spent more on parts than i paid for the car so this is really starting to bother me

 

When did the problem start, after you replaced everything or before? was everything changed at once or one at a time?

 

the problem was from before... i've replaced all the things over the last year.. when ever i had spare cash i would replace something

but nothing has fixed the problem.

 

Does it run any better if you play with the distributer? you can try spraying intake cleaner around the seals and intake when she is running and see if the rpm spikes. this would show a vacuum leak. There is a possibility that the harmonic balancer slipped and moved the timing mark. if its been dropped or the rubber decays the weight has a possibility of slipping around the spoke. this is rare though... but it might explain the running better at high rpms but not the running better when hot. make sure all plugs are connected.