ODB-II

[slimslob]

Read what I said again, I didn't say engine speed was the cause for less vacuum. I asked when a motor pulled less/more vacuum and gave 2 scenarios.



more vacuum = less air present. (idle) The motor is sucking cause the TB or butterflys are closed. less air = less fuel.

Less vacuum then more air present (driving down the road)and more fuel then needed then more power.

And I was answering that first question.

[BillyCarpenter]

And I was answering that first question.

It's all good. My point is this.


You can remove a small vacuum hose and your car will run very rough at idle but when you start driving down the road you can't even tell the vacuum hose is off in many cases.


Why?

Because vacuum is much higher at idle than running down the road. That's all I was saying.

[KenB]

Another use for OBD2 is for checking emissions.

If your locality (state or county) requires emissions testing, the tech now plugs into the connector under or near the dashboard, and gets a reading within a matter of seconds.

In the past, or with older vehicles, they needed to put a sniffing device in the exhaust. They operated the engine at different RPMs, under load (a set of rollers under the drive wheels - a real treat with 4 WD), which takes much more time. At least that how it works in Ohio.

I have heard that OBD3 will actually broadcast the readings through the vehicle’s GPS, if so equipped. Hello, Big Brother.

[BillyCarpenter]

Another use for OBD2 is for checking emissions.

If your locality (state or county) requires emissions testing, the tech now plugs into the connector under or near the dashboard, and gets a reading within a matter of seconds.

In the past, or with older vehicles, they needed to put a sniffing device in the exhaust. They operated the engine at different RPMs, under load (a set of rollers under the drive wheels - a real treat with 4 WD), which takes much more time. At least that how it works in Ohio.

I have heard that OBD3 will actually broadcast the readings through the vehicle’s GPS, if so equipped. Hello, Big Brother.

Yep. From my understanding, the onboard computer works this way when it comes to making an engine produce less CO2.


Anyone familiar with Fuel Trim? This has to do with air/fuel mixture. If there's too much gas vs. air, that's a "rich" condition and the catalytic converter can't burn off all the C02. If there's too much air vs. fuel, that's considered a "lean" condition and again the catalytic converter can't burn off the C02 as efficiently. There's usually 2 C02 sensors. One before the exhaust goes into the catalytic converter and another sensor behind the converter to read C02 after it's passed thru the coverter.


The computer strives to keep a perfect balance of air/fuel for burring off the most C02 in the catalytic converter.

[NeoMatrix]

Yep. From my understanding, the onboard computer works this way when it comes to making an engine produce less CO2.


Anyone familiar with Fuel Trim? This has to do with air/fuel mixture. If there's too much gas vs. air, that's a "rich" condition and the catalytic converter can't burn off all the C02. If there's too much air vs. fuel, that's considered a "lean" condition and again the catalytic converter can't burn off the C02 as efficiently. There's usually 2 C02 sensors. One before the exhaust goes into the catalytic converter and another sensor behind the converter to read C02 after it's passed thru the coverter.


The computer strives to keep a perfect balance of air/fuel for burring off the most C02 in the catalytic converter.

The optimum FAR (fuel air ratio) has a Stoichiometry of 1.0.

The EGR (exhaust gas recircluation) controls the mix of
oxygen flow in the intake manifold to control how hot the FAR burns
,which is used to control toxic exhaust gas emissions.

The EGR is an on going problem for some diesel engines.
The EGR only works "efficiently" while the engine is newest.
The ECU (computer)controls when the EGR comes on, an what range of FAR.
Of cause there are a lot of other sensors MAF, MAP, Lambda, Oxygen1-8.
that are monitored by the ECU to get the FAR optimal.
And all this is calculated at atmospheric sea level. When the vehicle is driven in the mountains, the atmospheric pressure changes giving a whole different FAR.
The vehicle ECU has a set of maps that make allowances for different driving conditions.

[BillyCarpenter]

The optimum FAR (fuel air ratio) has a Stoichiometry of 1.0.

The EGR (exhaust gas recircluation) controls the mix of
oxygen flow in the intake manifold to control how hot the FAR burns
,which is used to control toxic exhaust gas emissions.

The EGR is an on going problem for some diesel engines.
The EGR only works "efficiently" while the engine is newest.
The ECU (computer)controls when the EGR comes,on an what range of FAR.
Of cause there are a lot of other sensor MAF, MAP, Lambda, Oxygen1-8.
that are monitored by the ECU to get the FAR optimal.
And all this is calculated at atmospheric sea level. When the vehicle is driven in the mountains, the atmospheric pressure changes giving a whole different FAR.
The vehicle ECU has a set of maps that make allowances for different driving conditions.

We're getting deep into Fuel Trim and it gets even more complicated. There is SHORT TERM fuel trim and LONG TERM fuel trim. Any good mechanic really needs to master the fuel trim concept. This video explains it well:


PS - If anyone watches this video and truly takes the time to understand it, you'll be well on your way of being able to troubleshoot a lot of engine problems.

[KenB]

This is a little off topic so forgive me.


When I wanted to learn networking or how to use WireShark or car engines, there were a million videos that explained it in great detail.


When I wanted to learn about a particular problem on a copier.....you can't find shit on the internet. No articles. No videos. No nothing. Except for this site. Copier information is a closely guarded secret.

It’s a numbers game.

There are far more cars in the world (at least in the US, anyway) than there are copiers.

There are some secrets that auto makers keep to themselves, too, that they don’t like being shared.

[BillyCarpenter]

It’s a numbers game.

There are far more cars in the world (at least in the US, anyway) than there are copiers.

There are some secrets that auto makers keep to themselves, too, that they don’t like being shared.

True Dat.

I wonder if a group of copier guys started their own YouTube channel on copier repair if it would be successful? I know I'd tune in. I can think of a few guys on this site that need to be recruited.

[BillyCarpenter]

The optimum FAR (fuel air ratio) has a Stoichiometry of 1.0.

The EGR (exhaust gas recircluation) controls the mix of
oxygen flow in the intake manifold to control how hot the FAR burns
,which is used to control toxic exhaust gas emissions.

The EGR is an on going problem for some diesel engines.
The EGR only works "efficiently" while the engine is newest.
The ECU (computer)controls when the EGR comes on, an what range of FAR.
Of cause there are a lot of other sensors MAF, MAP, Lambda, Oxygen1-8.
that are monitored by the ECU to get the FAR optimal.
And all this is calculated at atmospheric sea level. When the vehicle is driven in the mountains, the atmospheric pressure changes giving a whole different FAR.
The vehicle ECU has a set of maps that make allowances for different driving conditions.

By the way, the correct stoichiometric mixture for a gasoline engine is about 14.7:1....not 1.0

[BillyCarpenter]

One more comment about code readers. They're not very useful if a person doesn't understand how things like Fuel Trim work. Like I said, it's much like a copier. The error codes don't make a lot of sense if you don't undserstand how a copier works.


Once you understand how a engine operates along the the sensors and computer, that code reader/scanner makes short work of most problems.