91 4runner running terrible

[scottjkj]

Ok Im driving home then all of a sudden my 4runner starts lurching and hesitating. I get it home and start to check it out. It idles a little rough but runs fine when you gas it a little. Now when you give it more gas it smells real rich and I could see black smoke coming out the exaust along with what looks like carbon. I got no trouble light. After it warms up a bit it wont even idle, it dies. I changed the o2 sensor,fuel filter, plugs, rotor and distributor and still runs terrible. I even put fuel injector cleaner in it. When it idles I would pull a plug wire off one at a time and each one would just lower the idle slightly so I figure what ever it is its universal for every cylinder opposed to maybe an injector or two or a missing spark, they all spark fine. It almost seems like something is telling it to run rich. Couldnt find any vacum leaks and the egr valve seems fine. any ideas....

[Brian R.]

Coolant temperature sensor?
MAF sensor?

[scottjkj]

Wouldnt the check engine light normally come on if it was the mas af sensor, I would think if its running rich or lean the o2 sensor would pick that up and show a trouble code. How about the coolant sensor would that show a trouble light and code?...THX

[4Wheel]

Ok if your exhaust is so rich it is "black" way too much fuel.
You're right it soounds like a global problem with all cylinders unless,
one or more injectors are not shutting off not usually a failure mode.

The engine light doesn't come on for all errors but they have been logged, go ahead and install the jumper wire and see if it flashes a code.
Might help.

What do any of you think about unplugging the injectors it shouldn't even fire at all, BUT what if it does? Will the ECU "sense" that they are unplugged and shut down?

Have you recently for any reason molested the engine wire harness recently? That might be a place to look.
I am starting the tedious process of a COMPLETE continuity check of ALL wires in the harness I have found two broken wires already insulation is as brittle as glass.

Fuel restrictions will only make it run lean check to see if there are any "hidden" codes, (oh yeah some codes only become visible on the "second trip" that is after the ignition has been turned off and the error returns on the second trip is the code passed through)

"If you can't open your doors the snow depth is just getting FUN!"