Running rich

Asked by Sep 28, 2016 at 01:59 PM

Question type: Maintenance & Repair

Have a 96 gmc that keeps burning bank 1 sensor 2.
I have run test on every thing I can think of and
replaced several items.  Timing is good plugs good,
distributor and rotor are new. I'm am fixing to put
my 6th O2 sensor in. I have replaced the cats as
well because the truck has 298k on but new motor
about 2 years ago and it has not been right since.
Spider injectors were new when rebuilt.  What else
is there???

8 Answers


EGR, PCV, The other sensors MAP. If you know the O2's are good do not replace them

Hey enginecreator. EGR was fine PCV fine but have not checked the MAP. It throws no codes or will it throw a code the MAP? This is the craziest thing I've ever tried to fix. What is it After replacing the 02 sensors on bank 1 (6) times would still make it keep burning them out. This gets a little expensive if you know what I mean.


o2's do not go out that fast they can handle the heat. Is this the 4.3L V6?


Also is the code indicating low or high voltage?


Bank 1 sensor 2 is after the cat. Reasons for setting code:: Faulty o2 sensor, Exhaust leak near the rear sensor, Plugged catalyst, Short to voltage on O2 signal circuit, High resistance or open on O2 signal circuit, Engine running very rich or lean, Engine misfire condition. Fuel pressure very high or low - fuel pump or pressure regulator

It's a 5.7L. Yes it's after the cats and they are brand new. Only have maybe 1500 miles on them. How can I tell if it's high resistance or open 02 sensor. I had engine misfire before but change rotor and cap. My exhaust pipe looks like it has black soot around the edge and inside of it as well. I'm going to check wires to make sure they are not shorting out. Last fuel pressure check the guy said was fine. Compression check was fine. Hopefully with your info I get it running right again.


The black soot means it is running rich. Extra fuel going threw, either its too much to get burned up or misfire. Leaky injector, bad plug or wire or coil, faulty fuel gauge, bad air filter, TPS it can cuase a some wild symptoms low idle, stalls hard to idle or accelerate and symptoms that mimic misfire and the IACV causes high or low idle if bad or surging or stall if failed completly. Voltmeter on ohms to check resistance if it real high there is possible insulation scratch off. Checked in volts dc mode Open circuit means its shorted out or no voltage this may mean part of the time as in the wires running to o2 short out sometime, so you may can move the wires too while testing for volts at o2 to see if the power changed or drops off and comes back if so that break in wire need located and repaired and it may not be visible if the wire is broke inside the insulation. On the resistance the lower the better. and can checkit while moving the wire around too if it changes it can also indicate that the wire or wires are rubbing or shorting and needs located and fixed.

Okay I will check all of these things out which will take me some time. Thanks for info and I'll try to find its way back to running good

Your Answer


Maintenance & Repair Experts

  • #1
    Tom Demyan
  • #2
  • #3
View All

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.