Seems to be running rich, black smoke from exhaust, when i'm driving it runs great but when i stop idle drops way down but does not stall i tap gas pedal and idle comes back up but smokes black smoke till i drive off so my question is can the air / idle control valve be adjusted and if so how ?? ps i did pull a code 171 witch said it was lean
No. (but the isc valves loves to stick but will not cause black smoke)
the 4.0L is one of 5 million made, it's well known,
the black smoke don't lie. it's rich and the cat seems burned up too.
as with black smoke the cat will try to catalyze all that and glow red hot. is your cat missing?>
so why not believe the code 171, its real and is catastrophic failure. there are 2 engines here, FED and California.(exhaust)
(2 different exhausts and sensors there.
as they say, fix what is OBVIOUSLY bad, 171
(find why using tools or inspections)
Fuel System Lean (Bank 1)in most cases the exhaust is cracked near B1S1 0xy sensor
this causes it to stick at 0volts, (lies) and the PCM sees that obvious lie then goes rich. (limphome rich)
if the pcm cant measure oxygen, it must now guess at fuel trim.(bad that.)
it goes rich, so you dont melt pistons running lean.
(by design)
bad front oxygen sensor (aka , up stream bank 1)
in calif cars, it can have a split exhaust on the I6 and have 3 sensors. (hope not yours, do look..)
most have 2 sensor, front and the useless behind cat sensor(B1s2)
S2 is useless for running mix, the rear is for smog test the cat.
so it rich, and now misfires. and the spark tips are black.
and it misfires to bad it can even idle, sure. (Drops)
the cause, is too rich.
the 171 means the PCM sees it stuck at 0v forEVER.
there are in fact other causes.
but these 2 are top cause.
on all 3 of my 4.0L engines
the exhaust manifold cracked on the under side.
side facing block. (i use a hose to ear to hear the putt putt puts, (with FULL PPE protection from burns from a dead cold engine.) ask how.
even the SST exh. man. did that.
or the header flange gasket is TOAST. (that too putts when bad.)
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