1994 buick roadmaster

we have a 94 buick roadmaster and when we turn it on the side with spark plugs 1,3,5 and 7 throws out black carbon looking stuff once it warms up it stops throwing it out we have changed out 4 fuel injectors,the fuel
pump, the fuel pressure regulator and all the spark plugs also the service engine light is on and it won't show any codes and we can't get it to turn off.anybody know what this could be? any and all help is greatly appreicated thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.