need help

[ruberpoliceman]

Hi all, i have a 1986 caprice 305 v8 4bbl rochester Q-jet. when i first bought it it ran like shit missfired and all, since then ive changed the air filter, fuel filter, oil filter, oil, 02 sensor, knock sensor, timing chain, spark plugs, plug wires, distributor cap, rotory button, set the timing, and rebuilt the carb but am still having the same problem.

when i last checked the timing it was right but i noticed that when the engine misfired the mark on the balancer jumped way off the set point what could be causing this? also when i cut the switch off it still runs on and sometimes never cuts off unless i hold the the choke closed what would cause this ??? . ill take any help i can get thanks..

[PeteA216]

Did you change the electronic spark contol module? Its the "computer chip" undert the distributor cap. It could also be you ECM is shot.

[RamAir81]

Check and ensure that your Harmonic balancer is still servicable and not lose or separating at the rubber in the center. What is the milage on the caprice? It could be time for a timing chain. What idle is set when the car is in park? Check the choke also for lock out (stays vertical... open when engine is hot). I'm running 10* initial time and when I run regular unleaded sometime I get the dieseling (run on ) when I shut my car off and the outside temp is in the nineties. However,with mid-grade fuel I have no problem.