Combustion 101:                               

(To the   Chemist perfect is, Octane burn simplistic  ) (& related to smog)
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O  < see water there?   See the Wiki at un-catalyzed... page sections
When the engine (and controls) work right every drop of fuel is burned and very tiny few O2 atoms remain.
See that H18 that  is very dense hydrogen, low cost, liquid, portable, safe and wonderful stuff. (and don't need a NASA engineer to contain it, as pure Hydrogen needs)
The Simple explanations for burning  are:
FUEL (GASOLINE)  and  LOTS OF  AIR  ARE  Combusted to FORM carbon Dioxide and water.
Combustion is also called burning the fuel or extremely rapid oxidization. (but not ever violent explosion or detonation modes)
(  just about  all things can burn in pure oxygen with just a  tiny spark)

Some say oxygen does not burn, (correct ) but just about all things burn very well or too well?, in sufficient concentrations of oxygen (even diamonds can burn)
In our physics class we dropped pure steel wool , (tiny parts red hot with match heated) into pure oxygen, the steel wool went bye bye, gone in a flash) we burned steel up, in class. !
In our engines, this is done using fuel and 20% oxygen (called AIR), at  high pressure and needs spark (Nikolaus Otto Cycle engines,  spark to triggers this burn event)
A diesel engine, uses so much more chamber compression (2x), it self ignites, so has no need for any spark ignition systems.
Poor or bad combustion, is the root cause of all engine running badly pages, MisfireWon't startflooding, lost  engine power even excess EGR actions. (or stalls?)

See a crude (no pun) history of oil:

Burning  real fuel: "Gasoline"
The modern engine burns these HC  fuels ( much of which ends up as CO2  (carbon dioxide and water) but Gasoline creates 16 CO2 + 18 H2O. (the H2 in the water  H2O. is wasted energy (didn't go to the driving axles)
CO (mon oxide) is deadly, CO2 is not deadly we exhale it in every breath as do most plants.  But CO2 is  global warming gas they say. CO2 is not toxic unless you breath it in a too rich state, like what happens (can) in Submarines. (at about 6% or 150 times normal C02 humuns die.)
Our air is about  400 parts per million CO2.
We all know ,that all substances are toxic (even pure water is) if used to excess.  By toxic we usually mean, in minor amounts toxic, or if in California, all things  cause cancer, even hamburgers....
Carbon Monoxide: (yes we used old tools that measured CO , to tune engines to hear STOICH, back in the day)
CO , is a deadly sneaky invisible poison, and wastes FUEL and causes lower MPG (fuel economy)  (not C02 but CO is  very very toxic "Carbon Monoxide))
Under perfect combustion, even the carbon burns, and even diamonds can burn up in a hot rich oxygen environment (at super temperatures), that would destroy any engine)
CO is created, when the engine lacks oxygen. (same with all  BBQ and all wood fires , that kill many people ,every year)
In fact, a cheaper cost CO measuring  meter , allows  tuning any engine for maximum economy and max MPG, and vary low CO gas (very tiny) See graph below for proof.
NOX, is next and is deadly, and happens in all engines that burn to hot, or lean.  Most cars make these gasses under heavy load flogged up hill, (the EGR reduces it as does the three way CAT,, together)
Nox  (Nitro's Oxides (toxic to all life) is formed by extreme lean fuel mixtures and huge excessive combustion heat.  It is formed from the free Nitrogen and oxygen in the air (by accident during combustion).

Ok, that is enough history and the like, what makes bad combustion?
In all cases, of misfiring and most causes of lower engine power can be traced to the below many items.
In each case, there are simple and cheap tools, we can use to find , true causes of the problem.
  1. Weak or no compression on any cylinder, 
  2. Weak or no spark , on any or all cylinders, or timed wrong, or on old Carb. engines, a dead advancing system, inside the distributor (89-90' Suzuki's have this...crude advance)
  3. Weak or too much fueling , the latter causes Deadly CO emissions. (lean AFR ,or Rich AFR) (air fuel ratio)
  4. Coolant Water (and anti-freeze) leaking in to the combustion chambers. (wreaks havoc)
  5. Knocking (a.k.a., Ping and Detonation !)  (engine will be damaged, if allowed to continue) (lean mixtures caused) and lower engine power..
  6. EGR main stuck open (excessive EGR flows) or the EGR modulator gone WILD. (the EGR modulator air vent is blocked , is common after 20 years of dirt sucked in, there, clean it and cured)
  7. Low or No air for the engine ? caused by air cleaner clogged?, or the ISC/ICA (air-valves) both stuck closed? engine stalls.  (this causes flooding cranked or stalls running)
  8. The CAT is melted and the engine can no longer breath at all or is greatly restricted.  (note very low vacuum in the plenum?) Caused by gross RICH misfiring of engine and then driven HARD.
Most Failures above,waste fuel like mad, but a tad lean will not.. (but a tad rich, makes more power)
Dynamics:  (end to end, from combustion and car driver and then to spin the axles and tires) My car has an MPG gauge and a wide band 02 meter, that makes all this simple to see in real time.

The  HOT engine (car) at idle and cruise runs  at STOICH. On demand of  the car driver  (Acceleration) the AFR (air fuel ratio) goes to the RED line, then returns to STOICH , if on flat ground, and steady right foot.
The Driver , going to Wide Open Throttle (WOT) puts the AFR to graph red line (and holds there at WOT )
If the driver  of a car, cuts the throttle totally, moving fast in gear the AFR goes max lean, or cut fuel MODE , my MPG gauge shows 200 MPG! (Or infinity)   (miles divided by 0 is infinity, most scan tools shows 200 for MPG)
( distance div by fuel = MPG) if fuel is zero?) sure.
Most  errors listed above, make excessive smog. (the red line at below graph, makes smog too (tad high HC), but is 100% normal accelerating.
Some modes make deadly CO.(too rich)
Perfect combustion makes the most CO2, the so called global warming gas. (Climate  Change?, toss coin) ( Get ready for more punitive higher fuel taxes and all things cost more... ALL)
When you hold your breath, your lungs fill with CO2, so stop that... (LOL)
There are 1 Billion cars running around  on earth now.  (more if you count , non registered vehicles and off road, yes, vast....)
There will be lots more of CO2, emitted, now and for the rest of my life. ( 66 yo) The USA EPA does no rule or run the world. sorry, it's not going to happen. end rant.  (how many China Coal plants went on line in last 10 years to now)? vast.
One way to reduce CO2 and still run on gasoline, is to use a smaller engine (1.0Liter?) (w/turbo?) This is a low cost solution, not used much in the USA but , big time common in Europe. (they are savvy , no?)

In the future, we might have  a detonation mode engine, that is 2 times more powerful, than the normal ICE piston  engine.   Sorry , No hope or a flux Capacitor? (LOL)
We have QT prototype barely running only ,Called a Quasi turbine "QT".   It has far greater efficiencies.
(ICE or I.C.E means internal combustion engine. (piston type in this case))
The variable displacement Piston engine or QT engine, can be made way smaller and if more efficient, there will be less CO2.
This will cut CO2 emissions, because the QT  uses less fuel and is way more efficient, but sadly most Detonation mode engines blow up.
Many car makers have engines that run on only the number of cylinders needed.  1 to 8? Saving lots of fuel, going slow or stopped.
Worst of all: (A travesty if you ,think about it,  this 75% loss...
Current engines, waste 75% of the fuel we burn , in to waste heat and other losses.   (QT Engines, or the like are one promise)

Automotive technicians: ( or the old school name, "your friendly mechanic")
One problem for technicians is that , measuring the gases of combustion, is near difficult with an installed catalyst in place. 
Many shops add a 18mm bung port to the header pipe and attach their wide band oxygen sensor to here and check engine tune . (or smaller plug hole  for 5 gas tests)
See graphic for gases  below , these measurements are PRE (before ) the modern TWC, three-way-CAT. (a custom test port was made (welded on to header pipe)
All modern car engines , are tuned to run at near Stoich. Note that the deadly CO is very low, and almost all oxygen is consumed.
Engine Cylinder compression rates, set the upper limits for what happens here, so that we burn the fuel and not detonate it. (call ping/knock ).
This old tool still sold  allows you to see combustion; go for the BLUE.
The key parts to avoid are NOx gas (toxic) CO (toxic)  and last unburned fuel HC.
This chart below is from a very expensive 5 Gas Analyzer. $10-20k expensive.  (but if you have an old CO meter, this works great to get CO below 1 %)
Many drivers think their car runs perfect, but in fact it may not.  (In fact, if the O2 sensor is bad, the engine can in fact make MORE power, see red line below , "BINGO")
Perfect, is burning all fuel and not making  vast amounts CO or NOx !

To the right of Stoich, the engine lacks power (lean burn)
Your cars engine brain, ECU/PCM is always trying for lowest smog, and best MPG.  (for sure great)
One trick a good tech. can use, is buy a new front (upstream) Oxygen sensor and then trust it to tell him (scan tool) the oxygen mix, by watching it closely and testing by adding air or lowering fuel pressures. (messing with fuel pressures is the best trick to watch fueling rates and the 02 sensors readings live)

The ECU  works hard to do that, if you keep a good Oxygen sensor and proper fuel pressures, it can happen. ( The ECU will show closed loop status, to signal it is running at Stoich)
The mechanic (tech) knows, that all the below is useless if the engine misfires. Misfire causes, must be found and cured first.
Each misfire sends raw fuel "HC", and  Oxygen @ 20% and nitrogen out the end of the tail pipe (or makes the CAT burn red hot)
"NO" is also called NOx ( that causes acid rains, and eats up human lungs,etc) Your smog station calls this "NO"
One can also monitor EGT , exhaust gas temperatures, to tune to peak, like private pilots do. (a mixture knob, they have, to keep AFR centered, as the climb to higher altitudes)
The best way, (bang for buck) is with a portable wide band oxygen sensor, to tune or check state of tune on any ICE engine.
The AFR gas graphic #1  is below.  STOICH burn , burns every drop possible, of fuel. (lean burn engines, in some Hybrid cars, run near the blue line)

The fuel ratio  is by weight or mass, not volume.  14.7 pounds of  air and 1 pound of Gasoline. 
(Ever seen 15 pounds of air, sure its 1400 gallons of air. imagine a big round tank  6 feet in diameter and 8 foot high, yes lots of air.)
(and is 280 gallons of oxygen (gas form) in the 1400 Gal. of air ) (at sea level and standard temps and pressures STP)

A short history on fuel and combustion, with some myths debunked and interesting facts:
Long ago, Cavemen learned that fire was good to keep warm, many had an infinite supply, but you get heated  3 times, to get hot, cutting down tree, bucking/chopping it, and then burning it .
That 's not all  fun and game's, nor the stink , smog or Carbon Monoxide "CO", the silent killer. 

Many people are killed  each year, via the CO , toxic fumes with BBQ burning in confined spaces or boats that run nasty combustion (docked and idling) (or boats idling in confined dock areas, don't do that)
Do not park a lawn mower running or an electrical generator near an air vent to a home or RV. (both are "CO" rich engines)
Today, we have a rich Hydrogen based fossil fuels laced  with carbon, and both elements can burn. (but our  engines only burn the H atoms )  See periodic table.

This fuel is called, Petroleum , or  hydrocarbons "HC" fuel, that chemists show this  as the   molecule "2 C8H18".  (note, the many 18 H atoms there and  the carbon)
This crude oil, is not renewable, but we will have  methane , forever, and the earth will produce this for us, and is called "NG", natural gas, to the average person. 
Engines run just great on NG, or LNG, liquid Natural Gas , as does propane (butane) LPG and Ethanol.

The crude oil petroleum  (aka:Rock oil)came from millions of old dead vegetation of vast kinds, even huge Plankton deposits (we have DNA signature proof !  + + and chemistry tracer poofs)
A barrel (42 gal.) of crude oil (rock oil) is near 1/2 gasoline "naturally". (the rest is also, very valuable, "for plastics, & tar"  an endless list, adds here....nah, you can Google it.)
"The majority of oil deposits are Mesozoic or Cenozoic in age.  66 to 252 million year old !"  The the moniker "fossil fuels"
This Crude oil is just ancient SUN storage. The SUN makes all energy on earth (besides internal atomic ! heat, at earths core)
The First oil here in the USA was in very shallow formations. Read Dirt cheap to extract.  (the first oil wells were created by seeing leaks of crude on the serface of the ground)
They had no use for Gasoline then, so what was left after using it to distill out some lamp Kerosene ,the gasoline was DUMPED into rivers, (omg yes), (no more whale oil to be found now...1876) Standard Oil, company, made the best lamp oil.(pure)
Then Otto cycle came town.  (tin lizzy's and motor cycles ) and the gasoline dumping ended, after about 1861 (first cars started to be sold)
So, burning this crude oil products, in its gasoline form or gas, this is our "current hydrogen economy."

H2 myths:
See here, for the false Hydrogen economy.  The truth about getting , converting and storing H2 pure gas.
Why on earth would you waste  hard cash, and energy losses , removing (steam splitting ) natural Gas to get
H2, when burning the NG is ready , free, and at hand to run this engine?
Dang ! (just to look cute, or Green ?)
NASA does it for only 2 reasons:
They use LOX + LHG  at great costs and lots of smog to make it. "liquid oxygen and liquid hydrogen fuel"

A Parting shot:
The earth will run out of useful arable land ,way before Crude oil.  (baring any  5 billion die off of humans )
The proof, is horizontal drilling and fracting technology, has vastly improved production, here and else where.
In 2014 (October ) the USA is now exporting fuel from Texas,  (shock) after 50 years,of not.
We can not feed much of the world, with horse drawn plows and reapers... that  point of time, has ended, we use FUEL now to make and produce and deliver food on a vast scale,  ending fuel, ends the lives of about 1/2 the people on planet earth, may be more... want to find out?
Agra-business is FUEL powered. 
ODD but true:
In school , we ran engines, on dirt (not sand,) and wheat flower, not just liquid or gaseous fuels. It can also run on Coal dust.
Lots of fun in school all that .... and all students in SHOCK !  Just what will burn ?, we ask  Mr. teacher,  answer, "organic mass of any kind, (dry) and dead."
Food for further thought? (or will we burn food? we are, with Ethanol) << wasting Arable land too !
During WW2,  in Fuel-less Japan (no liquid fuels, for civilian use) the folks made cars and truck to run off of  powered dung and rice shell.  (don't ask how much nasty smoke that made... or the stench)

Jargon:  (why jargon?, easy, nobody likes to type Air fuel ratio over and over (AFR), endlessly, nor Engine coolant Temperature sensor (ECT).  Full list here
A Short list:
H2 , Hydrogen in it's normal gaseous form.
O2, Oxygen
EGR, Exhaust gas recirculation (Nox reduction) {Nox a deadly nitrous oxide, gas}

HC = Hydrocarbon, Unburned fuel.
CAT = catalyst exhaust device (the smog filter is a good simple name) On modern cars, its a TWC , Three way CAT, or 2 way filter.(if you will)
QT engine, Quasi turbine, or better, detonation mode engines (ICE, class)
(ICE or I.C.E means internal combustion engine. (piston type in this case))

The ASE/SAE , true list is 4000 names. we will avoid  99% of those.

version 3:  12-29-2004