Question about 1999 Buick Century

2 Answers

Fuel mixture is too rich, O2 sensors replaced but still reports O2 sensor is bad. What else could problem be?

Posted by on

Ad

2 Answers

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

    President:

    An expert whose answer got voted for 500 times.

  • Master
  • 1,857 Answers

Need to know what the code says. need the code so we can check what the procedure is .

If the code is referring to low or high input that usually means you have another issue. Low input would mean something like a vacuum leak or something that would cause excess air to pass over the 02 sensor or sensors. If the code is high input or rich as you stated then you have a fuel presuure issue or sensor related issue that is keeping the fuel pulse width high. Using a data scanner will be about the only way to figure this out without just throwing parts at this. For all anyone knows its possible the computer failed.

Never trust a parts house to recommend a part. All they can do is give the code and then its up to you to diagnose it

Posted on Jul 29, 2010

Ad
  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Superstar:

    An expert that got 20 achievements.

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

  • Master
  • 10,319 Answers

O2 sensors that are bad for awhile will affect the MAP sensor to go bad as well. Go to Auto Zone and they will provide a FREE scan of the engines computer. They will tell you what needs to be replaced or looked at

Posted on Jul 11, 2010

Ad

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
goodluck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

2 Answers

2003 pickup. What are the probable causes of DTC P0171?


Since you have replaced the sensor, my first guess would be low fuel pressure or a vac leak.
Code 171 means the computer can not make the fuel mixture rich enough to make the sensor switch from lean to rich and back.

Jun 24, 2015 | Dodge Cars & Trucks

1 Answer

2004 Toyota Camry - Check engine light has been coming on intermittently for a year. When reading the codes it states Knock Sensor and O2 Sensor Bank 1. The car is very sluggish when the light comes on....


I would tend to say the knock sensor is a result of the 02 sensor, because if it is not reading correctly it could be reporting the engine is running to rich, there for leaning out the air fuel mixture resulting in knocking which is then picked up by the knock sensor. I would start by replacing the O2 sensor in bank 1.

Sep 08, 2011 | 2005 Toyota Camry Solara

1 Answer

Miss fires at ideal smells like to much fuel out of exhaust. Runs better at higher rpm. 2000 Pontiac Grand am 2.4L


If it improves with rpm, I would suspect a stuck injector (not closing) causing your engine to run rich, or a bad temperature sending unit. You should check for fault codes (they will do this for free at Autozone). You will most likely have a code for a bad oxygen sensor. Don't replace it until you correct the rich fuel mixture with the bad one unplugged. The rich mixture is the cause of the bad O2 sensor, not the symptom.
I you unplug the O2 sensor the ecm will substitute a generic value, allowing you to correct the real issue without destroying another O2 sensor. They are not cheap.
You can verify a stuck injector cyl by cyl by inspecting the plugs. If they all look the same, you may want to unplug the cold start injector and see how it runs.

May 12, 2011 | 2000 Pontiac Grand Am GT

2 Answers

1999 ford ranger 4x4 4.0L motor is skipping replaced camshaft sensor,crankshaft sensor,new coil pack,new plugs,wires,and replaced mass air flow sensor,now its still skipping and codes pulled are showing...


P1151 means a lean bank 2 O2 sensor
P1152 Means a rich bank 2 O2 sensor
P1309 Means miss fire detected
I would check your fuel injector for fouling
When they foul the will develop a drip
Causing a fuel fluctuation that will have O2 sensors reporting rich and lean voltage changes
This causes the pcm to adjust injector pulses making them shorter and longer.
causing more fuel or less fuel.
From this condition you may see plug fouling.
Also check for leaking or faulty fuel pressure regulator or restricted return line.
Most of the time it wont be a bad O2 sensor the O2 sensor is just doing its job.
You also have already changed the plugs and Map so there already out of the way.
If this helps please give me some feed back
Hope this works for you FixYa

Jan 29, 2011 | 1999 Ford Ranger SuperCab

3 Answers

Engine wont stay on when started unless you step on the gas,service engine soon " light comes on.Scanned it and you get code po172 system too rich.


Okay, lets start with you checking the fuel preasure regulator, this is a common problem with these the regulator leaks and the vac line connected to it starts sucking gas into the intake, this causing it to run rich and depending on how bad the leak is it will stall engine at idle, remove the vacuum hose from regulator and start engine then see if gas shoots out the vac connection on the regulator, if it does then replace regulator, hope this helps.583ec1c.jpg

Oct 18, 2010 | 1999 Pontiac Grand Prix

1 Answer

I have a holden 5litre v8 and am having problems with the fuel injection. the engine runs erratically at idle and blows black smoke when put under load. i have replaced, injectors, filter, regulator,...


Have the oxygen sensors checked or replaced.

This in an extract from an article on O2 sensors from an article at www.autotap.com:-
'The O2 sensor is mounted in the exhaust manifold to monitor how much unburned oxygen is in the exhaust. The signal from the O2 sensor tells the computer if the fuel mixture is burning rich (less oxygen) or lean (more oxygen).
A lot of factors affect the richness or leanness of the fuel mixture, including air temperature, engine coolant temperature, barometric pressure, throttle position, air flow and engine load. Other sensors monitor these factors too, but the O2 sensor is the master monitor for what's happening with the fuel mixture. Problems with the O2 sensor can throw the whole system out of whack.'

Oct 22, 2009 | 2007 GMC Acadia SLE

1 Answer

Check engine light was on. OBD II scan said both pre-Cat 02 sensors running lean. Also shows P0000 code which is a undefined code. S dash light comes every few days then transmission will stay stuck in 4th...


The pre cat sensors running lean does not mean they need to be replaced. They are are detecting a symptom. You need to know why.

If you are using a basic scantool (code only) you need to look up the P0000 code.
I thought this an odd code. I looked it up in my Autotap unit and it does not exist. The lowest # P (powertrain) code I have listed is P0016.

A regular scan tool, won't scan transmission or body codes, mu Auto tap doesn't either. You need a Tech 2 from the dealer for transmission codes.

First some history. The first O2 sensor was introduced in 1976 on a Volvo. California vehicles got them next in 1980, then federal emission laws made O2 sensors virtually mandatory on all cars and light trucks built since 1981. And now that OBD-II regulations are here (1996 and newer vehicles), most vehicles now have multiple O2 sensors, some as many as four!
The O2 sensor is mounted in the exhaust manifold to monitor how much unburned oxygen is in the exhaust. The signal from the O2 sensor tells the computer if the fuel mixture is burning rich (less oxygen) or lean (more oxygen).
A lot of factors affect the richness or leanness of the fuel mixture, including air temperature, engine coolant temperature, barometric pressure, throttle position, air flow and engine load. Other sensors monitor these factors too, but the O2 sensor is the master monitor for what's happening with the fuel mixture. Problems with the O2 sensor can throw the whole system out of whack.
The computer uses the oxygen sensor's input to fine tune the fuel mixture for the best balance of power, economy and emissions. The engineering term for this type of operation is "closed loop" because the computer is using the O2 sensor's input to adjust the fuel mixture. The result is a constant flip-flop back and forth from rich to lean which helps the catalytic converter operate at its best and keeps the average fuel mixture in proper balance to minimize emissions. It's a complicated setup but it works.
If no signal is received from the O2 sensor, like when a cold engine is first started (more on that in a minute) or the 02 sensor fails, the computer orders a steady, rich fuel mixture. This is referred to as "open loop" operation because no input is used from the O2 sensor to fine tune the fuel mixture. If the engine fails to go into closed loop when the O2 sensor reaches operating temperature, or drops out of closed loop because the O2 sensor's signal is lost, the engine will run too rich causing an increase in fuel consumption and emissions. As you might have guessed, that will set a code and turn on your check engine light.
How does it work? The O2 sensor produces a voltage once it gets hot. The sensor compares how much oxygen is in the exhaust to the oxygen in outside air. The greater the difference, the higher the voltage reading.
If you ever replace an O2 sensor (and if you're a DIY'er this is something you will do eventually), its important to remember that the O2 sensor needs to "breath" outside air to work. So don't put any grease on the sensor because it could block this air flow.
An oxygen sensor will typically generate up to about 0.9 volts when the fuel mixture is rich and there is little unburned oxygen left in the exhaust. When the mixture is lean, the sensor's output voltage will drop down to about 0.1 volts. When the air/fuel mixture is balanced or at the equilibrium point of about 14.7 to 1, the sensor will read around 0.45 volts.
When the computer reads a rich signal from the O2 sensor it leans the fuel mixture to reduce the sensor's reading. When the O2 sensor reading goes lean the computer reverses again making the fuel mixture go rich. This constant flip-flopping back and forth of the fuel mixture occurs anywhere from 2 to 7 times a second at 2500 rpm on OBDII vehicles, depending on what type of fuel injection system they have.
The oxygen sensor must be hot (about 600 degrees or higher) before it will start to generate a voltage signal. Many oxygen sensors have a small heating element inside to help them reach operating temperature more quickly.
Ok – that was a lot of info on what they do and how they work. The next thing to know is that trouble codes relating to O2 sensors are very common. But you really need investigate further before replacing an O2 sensor just because you got that trouble code. Armed with the information above on how often the O2 sensor "flips" back and forth and AutoTap or another scantool that allows you to monitor O2 sensor voltage, you can be certain whether the O2 sensor itself is really the problem. These sensors can be pricey, so don't just replace them the first time you see that trouble code!

The O2 sensors are expensive, diagnose what really is going on.

Jul 27, 2009 | 1999 Cadillac Catera

4 Answers

Truck won't start and died while driving


yes definatly its asking for more gas also check your gaslines

Jun 19, 2009 | 1999 GMC Jimmy

2 Answers

Car Trouble


Could be. Basically anything that makes the fuel mixture rich can contribute to the converter getting clogged by sending unburned fuel into the exhaust. So things like dirty air filter, weak spark from weak battery, bad plugs, spark cables, rotor, distributor cap, o2 sensor can add to problem. So yes ignition control module would be a suspect to get tested.

May 14, 2009 | 1996 Pontiac Grand Am

1 Answer

O2 element


Adjusting the voltage isn't the way to go. If the car is running rich, your primary O2 sensor has gone bad and it needs to be replaced. If you artificially lean the mixture out, and then the sensor fails drastically, you may end up with a lean situation that will damage the motor. Spend the $50 or so and get a new sensor. The one you want to change is the one between the engine and the catalytic converter - that's the one that determines your fuel mixture. The one after the cat only is used as a comparator for catalytic converter efficiency.

Sep 01, 2008 | 2004 Dodge Stratus

Not finding what you are looking for?
1999 Buick Century Logo

126 people viewed this question

Ask a Question

Usually answered in minutes!

Top Buick Experts

yadayada
yadayada

Level 3 Expert

76164 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22156 Answers

Jeff Turcotte
Jeff Turcotte

Level 3 Expert

8273 Answers

Are you a Buick Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...