what monitors you air/fuel ratio on new chevys?

[buffblazer]

my Edge cts will show me what my air/fuel ratio is as the computer reads it.

started out at 13.7 then over the course of a month it went down to 12.8 then down to 11.6 as of today.

threw 2 codes. P0175 and P0172 which are rich codes.

air filter is clean as a whistle and no other problems.

any idea why my ratio is dropping so drastically? i know 14.7 to 1 is the perfect ratio for power and fuel and i would expect a fuel injected truck to be able to keep that.

 

[Fordum]

As far as I know, nothing has replaced the oxygen sensor for fuel ratio measurement.
How is the truck running? Is it running rich or lean?
With a cat, I'm not sure you will see any soot or black smoke, but if its running that rich, you ought to see the cat glowing red underneath the truck at night after driving it for a while.

Since the oxygen sensor only measures the amount of oxygen in the exhaust, anything that robs it of O2 will show up as a rich mix.
The EGR valve can do it.
If the truck is actually running rich, then suspect the fuel pressure regulator, or a leaky injector.
But, if gas mileage has gone up, and it seems to be running lean, suspect a bad O2 sensor.

J.

 

[max 02]

You could try the MAF senser,I mean that you could get a can of MAF cleaner from the auto parts store,and give that a try. The mas air flow senser is on the intake tube. Might be worth a try? What engine do you got?

 

[buffblazer]

As far as I know, nothing has replaced the oxygen sensor for fuel ratio measurement.
How is the truck running? Is it running rich or lean?
With a cat, I'm not sure you will see any soot or black smoke, but if its running that rich, you ought to see the cat glowing red underneath the truck at night after driving it for a while.

Since the oxygen sensor only measures the amount of oxygen in the exhaust, anything that robs it of O2 will show up as a rich mix.
The EGR valve can do it.
If the truck is actually running rich, then suspect the fuel pressure regulator, or a leaky injector.
But, if gas mileage has gone up, and it seems to be running lean, suspect a bad O2 sensor.

J.

its smells rich, but i am getting decent fuel milage

 

[Russell]

Don't count out physical problems with the engine - perhaps you have a bad fuel pressure regulator or something similar?

 

[4X4HIGH]

There are a bunch of items that control air/fuel ratio. The TPS (Throttle Position Sensor), IAC (Idle Air Control), MAP (Manifold Absolute Pressure, if it uses one) or MAF (Mass Air Flow meter, if it uses it instead of a MAP), 02 sensor, CTS (Coolant Temp Sensor). Any of these are related to telling the ECM what the engine is doing so it can adjust injector pulse width which is basically your air/fuel ratio.

 

[ryan22re]

I would look for something that would give excess fuel or not enough air. The MAF could be bad or dirty. Could have an injector sticking open. Too high fuel pressure. Bad o2 sensors.

The thing to remember is that when the ECM thinks the engine is rich, it leans out the mix. When it can't lean the engine out any more and still won't switch from rich to lean it sets a code. When setting a rich code , the engine could be running dangerously lean (that is if the o2 sensors are faulty), which is why you may not be noticing a drop in fuel economy. I'd start by monitoring the O2 sensor voltage and see if it is stuck/flatline/shorted etc.

 

[Stomis]

Finding too rich condition by Stomis:

Pull plugs. Look for one fouled. If you find one switch the coil for that cylinder with the coil for another one. Drive it and check if the fouled plug moved.

This would indicate poor spark from a bad coil. Usually an OBDII car will straight up tell you cylinder # misfire though.

Again if you have a fouled plug check the injector the same way.

Make sure the coolant temp sensor is within spec. This is an easy one to just go buy, change, and return if its no better.

Check fuel pressure. This will tell you if you have a bad regulator. You can unplug injectors one by one and look for a fuel pressure increase. If you pull a wire off and the fuel pressure stays the same you found a stuck injector.

Check and clean the maf.

Unhook the battery and let everything reset.

Try all that and get back to us.

 

[fubar_k5]

My parents impala had the same codes pop up was trying to figure out what it was. Was talking to a guy at oriellys said to tap the maf with a screw driver, if the motor cuts out that means its bad. so i tapped the maf it cut out replaced it, and its been good ever since figure id throw that one out there for checking the maf if its true or not.

 

[1979jimmy350]

is the o2 value you are looking at the commanded afr or the actual? Just remember the factory narrow band oxygen sensors are only good for right around 14.7 afr after that they are not accurate at all. Has there been any mods done to this motor?

 

[buffblazer]

is the o2 value you are looking at the commanded afr or the actual? Just remember the factory narrow band oxygen sensors are only good for right around 14.7 afr after that they are not accurate at all. Has there been any mods done to this motor?

i have a cold air intake, exhaust and the chip

the codes only set when i was in extreme mode, i guess i should have been more clear, the air/fuel ratio is what my edge programmer says,

anyway that programmer could be reading it wrong.

the truck runs fine, i would never even know it wasent making 14.7 to 1 if i couldnt actually see it on a gauge.

 

[Stomis]

i have a cold air intake, exhaust and the chip

the codes only set when i was in extreme mode, i guess i should have been more clear, the air/fuel ratio is what my edge programmer says,

anyway that programmer could be reading it wrong.

the truck runs fine, i would never even know it wasent making 14.7 to 1 if i couldnt actually see it on a gauge.

Dude theres nothing wrong with the truck. The problem is your using a "programmer" on a gas truck. Its a fad and half a scam all at the same time. Diesel guys get big power from just adding more fuel because to an extent thats the way a diesel works. Gas isnt the same therefor dumping more fuel doesnt work without internal work that necessitates more fuel.

Honestly ditch the programmer its a waste. Theres loads of good shops across the country that can tune your gen III/IV motor better than the factory tune and net you that little gain over the conservative tune it rolled off the lot with.

O and btw if you truly want an accurate reading of your AFR get a AEM Wideband gauge and control box.

 

[Blue85]

I agree. If the truck runs fine without the programmer then the truck is fine. So the problem is...

If the code only sets in "extreme" mode, just don't use it. All that box can really do is add fuel and advance timing. The fuel won't help unless the default tune is too lean (possible), but after 13:1 or something you make less torque with a naturally aspirated engine. The spark won't help unless you're able to run premium gas or at least a colder thermostat. And the designers have no idea what your specific vehicle needs. It's based on averages, much like the factory cals, so the engine still isn't "tuned".

Your programmer doesn't know that you're at 11.something AFR unless you've added a wideband O2 sensor. How does it calculate this? It sounds like you just get one number, which is bull - every load (MAP or MAF) and RPM condition will have a different AFR. 11.5 is way too rich unless you have about 30psi of boost on it.

You can add a wideband to satisfy your curiosity (for a few hundred $), but unless you are tuning it yourself (not using a "programmer" box, but manually setting fuel and spark tables) or installing a turbo/supercharger, there is no need. They are a good tool, but they can lie to you, too. For example, when you get too rich it will misfire, so there's all this oxygen and it tells you that you are too lean, which will make it want to go even richer. When an injector or spark plug stops working, one cylinder stops firing and again there is all this oxygen, so you will tend to add fuel and load up the cylinders that are still working until the "average" AFR is correct.

 

[Stomis]

I agree. If the truck runs fine without the programmer then the truck is fine. So the problem is...

If the code only sets in "extreme" mode, just don't use it. All that box can really do is add fuel and advance timing. The fuel won't help unless the default tune is too lean (possible), but after 13:1 or something you make less torque with a naturally aspirated engine. The spark won't help unless you're able to run premium gas or at least a colder thermostat. And the designers have no idea what your specific vehicle needs. It's based on averages, much like the factory cals, so the engine still isn't "tuned".

Your programmer doesn't know that you're at 11.something AFR unless you've added a wideband O2 sensor. How does it calculate this? It sounds like you just get one number, which is bull - every load (MAP or MAF) and RPM condition will have a different AFR. 11.5 is way too rich unless you have about 30psi of boost on it.

You can add a wideband to satisfy your curiosity (for a few hundred $), but unless you are tuning it yourself (not using a "programmer" box, but manually setting fuel and spark tables) or installing a turbo/supercharger, there is no need. They are a good tool, but they can lie to you, too. For example, when you get too rich it will misfire, so there's all this oxygen and it tells you that you are too lean, which will make it want to go even richer. When an injector or spark plug stops working, one cylinder stops firing and again there is all this oxygen, so you will tend to add fuel and load up the cylinders that are still working until the "average" AFR is correct.

Well unless you have a standalone that wont happen anyway. Any wideband that hooks up to the factory computer needs a translator to convert the signal back to a narrowband signal.

 

[Blue85]

What won't happen? An incorrect AFR measurement due to misfiring? It makes no difference to the sensor whether it is scaling a 0-1V output or using full range. Oxygen is oxygen.

Some cars use WB from the factory, so no scaling is used. Most aftermarket WBs offer two outputs - a standard WB one and a narrowband simulated one.

But why do we digress? I think we're all in agreement that the programmer is giving incorrect O2 measurements.

 

[Stomis]

What won't happen? An incorrect AFR measurement due to misfiring? It makes no difference to the sensor whether it is scaling a 0-1V output or using full range. Oxygen is oxygen.

Some cars use WB from the factory, so no scaling is used. Most aftermarket WBs offer two outputs - a standard WB one and a narrowband simulated one.

But why do we digress? I think we're all in agreement that the programmer is giving incorrect O2 measurements.

No no I'm not saying that. I'm just saying you cant stick a wideband o2 sensor and expect it to jive with a stock ECM that used a narrow. Like you said its a different range.

Like you said he needs to ditch the tuner.

 

[buffblazer]

I agree. If the truck runs fine without the programmer then the truck is fine. So the problem is...

If the code only sets in "extreme" mode, just don't use it. All that box can really do is add fuel and advance timing. The fuel won't help unless the default tune is too lean (possible), but after 13:1 or something you make less torque with a naturally aspirated engine. The spark won't help unless you're able to run premium gas or at least a colder thermostat. And the designers have no idea what your specific vehicle needs. It's based on averages, much like the factory cals, so the engine still isn't "tuned".

Your programmer doesn't know that you're at 11.something AFR unless you've added a wideband O2 sensor. How does it calculate this? It sounds like you just get one number, which is bull - every load (MAP or MAF) and RPM condition will have a different AFR. 11.5 is way too rich unless you have about 30psi of boost on it.

You can add a wideband to satisfy your curiosity (for a few hundred $), but unless you are tuning it yourself (not using a "programmer" box, but manually setting fuel and spark tables) or installing a turbo/supercharger, there is no need. They are a good tool, but they can lie to you, too. For example, when you get too rich it will misfire, so there's all this oxygen and it tells you that you are too lean, which will make it want to go even richer. When an injector or spark plug stops working, one cylinder stops firing and again there is all this oxygen, so you will tend to add fuel and load up the cylinders that are still working until the "average" AFR is correct.

eh the wideban is really not something for me, i just saw the gauge reading and was curious.

I knew the programmer wouldnt give much power, it was more for the monitor.

Im in the process of talking to black bear perfomance about a new tune.