87 Ranger runs bad w/Black smoke

[Kid Kevony]

O.K. Heres one for ya! My 87 Ranger (2.9L) runs rough at mid speed when warmed up and spews black smoke. At wide open throttle it clears out and runs ok. Idle is good when cold and no codes are present. A fuel pressure check while cold checked out ok. In the past month I have replaced the Fuel pressure regulator, Fuel pump relay, EGR valve, and the Throttle position sensor. While I'm throwing parts at this $$ gobbler any more suggestions?

[2000mudder]

black smoke is unused fuel. it's getting too much fuel somehow. if it's ideling high it could be coolant temp sensor.it acts like a choke on computor controled cars. oxygen sensors measure air fuel mixture and when they go bad, they make the motor run rich to avoid detination from running lean. a vacume leak will make it run rich also. thats all i can think of for now.

[Psychopete]

I think I am having a bit of trouble understanding the post. Do you say it runs OK when it's cold, then begins to run rich when it warms up? It could be the o2 sensor going bad. The o2 get heated to 600 degress before the ECC will start reading data from it. It's located on the passenger side, follow exahust manifold to y-pipe, and right there it is. Unhook it temporarily and see if the issue still persists.

Did you actually run the codes, or do you just not have a CEL? The 87s have an emissions light, but no CEL. Or did you just not get anything at all from the ECC when you attempted to pull codes? If this was the case, did you use a code scanner?

Usually no codes and rich condition indicates ruptured FPR, but that can cause hard starts and rich when cold. It could also be the ECT or IAT, but the ECC should be seeing some sort of fault or erratic voltage.

Pete