Fuel pump, oxygen sensor, or other?


Asked by Oct 18, 2016 at 10:05 AM about the 2004 Pontiac Grand Am SE

Question type: Maintenance & Repair

I bought a car from a guy that said it only
needed an o2 sensor. It idles rough on
start, then smooths out once it's in gear.
My friend noticed there was a vacuum line
from the intake that lead nowhere and had
a screw jammed in the end where it was
supposed to meet a "t" section, so we
replaced that now since that and checking
the plugs the ses light has been flashing
once it gets above 30 mph.
Yesterday on the way to an interview I put
the car in reverse and it acted like it
wanted to die, so driving down the road I
stop at the intersection and the car just
dies and won't start. It wants to turn over
and even starts but then immediately dies
Just wondering if the o2 sensor can cause
this or is it more likely the fuel pump or
something else?

Car is a 2004 Pontiac Grand Am 3.4 L V6

4 Answers


Vehicle engines that have a bad oxygen sensor often run irregularly or roughly. Oxygen sensors can control or contribute to many different engine functions, including fuel/air mixture, engine timing and engine combustion intervals. A faulty oxygen sensor can disrupt any of these things and cause a rough engine idle.


I think you have something else going on, Check the pump pressure at the rails...


What do you mean by the rails? I'm pretty mechanically illiterate


I doubt the problem is the O2 sensor. Usually you can't tell they are bad except maybe for reduced fuel economy. Some one has been messing with the engine so it could be a lot of things. You may need a tuneup or a new IAC valve. (idle air control valve).

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