Tips and TricksTips and TricksNACAT 2001

Winnipeg, Manitoba, Canada

July, 2001

James D. Halderman

Sinclair Community College

Dayton, Ohiojdhalderman@aol.com

5-Gas Exhaust Analysis5-Gas Exhaust Analysis

Five-gas analysis is sometimes difficult for students to understand.

Tip:“Your Nose Knows”

If you smell exhaust, it is unburned fuel (HC).

5-Gas Exhaust Analysis5-Gas Exhaust Analysis

If your eyes water, it is oxides of nitrogen (NOx plus water around your eyes forms a mild nitric acid solution which burns your eyes).

5-Gas Exhaust Analysis5-Gas Exhaust Analysis

If you get a headache or feel dizzy, it is likely caused by excessive CO emissions.

Think of CO meaning “clogged oxygen” or not having enough air for the fuel or having too much fuel for the available oxygen.

Easy to Remember Easy to Remember SpecificationsSpecifications

w/o CAT w/ CAT

HC 300 ppm or less 30 - 50 ppm or less

CO 3% or less 0.3 - 0.5% or less

O2 0% - 2% 0% - 2%

CO2 12% - 17% 12% - 17%

NOX less than 100 ppm @ idle

less than 1,000 ppm @ WOT

Quick and Easy TipQuick and Easy Tip

CO should equal O2

CO = rich indicatorO2 = lean indicator

If both are the same, the mixture

is OK

5-Gas Sample Question #15-Gas Sample Question #1

What is wrong?

HC and CO2 = high and

CO and O2 = low

Answer to Question #1Answer to Question #1

The problem is most likely ignition (“spark stuff”) related.

It is OK for CO and O2 to be low.

It is OK for CO2 to be high (high efficiency)

5-Gas Sample Question #25-Gas Sample Question #2What is wrong?HC = 3 ppmO2 = 20.8%CO = 0%CO2 = 0%NOX = 3 ppm

Answer to Question #2Answer to Question #2

The exhaust probe was not in the tailpipe!

No carbons (CO and CO2) indicate no combustion occurred.

Tip:Think of CO and CO2 as ash left over

from a fire. No carbon – no fire!

Fuel Injection TipFuel Injection Tip

Use a stethoscope on an injector.Should hear a “clicking” sound not a

“clunking” soundStudents really understand fuel

injectors if they hear them work.

Quick and Easy TrickQuick and Easy TrickUse a stethoscope to listen at the fuel return

line from the fuel pressure regulator.

Quick and Easy TrickQuick and Easy Trick

If you hear fuel moving back to the tank, the fuel pump pressure is greater than regulator pressure.

If you do not hear fuel moving, the fuel pump or the fuel pressure regulator could be defective.

SensorsSensors

High Authority sensors include:02S – when in closed loopMAFMAPECT – especially at engine startTP

SensorsSensors

Low Authority sensors include:

IATBARO (if separate from MAP)TFT

Sensor TipSensor Tip

“If in doubt –

take it out.”

Tip ExplanationTip Explanation

A high authority sensor can be “skewed,”

Which means that it is working OK but not

accurately measuring the engine condition. If the engine runs better with a sensor

disconnected, the sensor is either defective or is somehow measuring the condition incorrectly.

If disconnected, PCM substitutes a replacement value.

Student ProjectsStudent Projects

Lighter Socket to MeterHeated Oxygen Sensor to MeterExtension Cord and Plug to Check RelaysFused Meter LeadFused Jumper WireWheel Speed Sensor to Double Banana

Plug

Lighter Socket to MeterLighter Socket to MeterFused Lighter Plug 274-335/Double Banana Plug 274-717Fused Lighter Plug 274-335/Double Banana Plug 274-717

Heated Oxygen Sensor to Heated Oxygen Sensor to MeterMeter

Extension Cord and Plug to Extension Cord and Plug to Check RelaysCheck Relays

Fused Meter LeadFused Meter LeadInline Fuse Holder 270-1213Inline Fuse Holder 270-1213

Fused Jumper WireFused Jumper Wire

Wheel Speed Sensor to Double Wheel Speed Sensor to Double Banana PlugBanana Plug

Neat WebsitesNeat Websites

www.autoclassroom.com (free)Free membershipIncludes useful worksheets, handouts, and

PowerPoint presentationsPlease send your “stuff” to the webmaster

so the site can grow

Neat WebsitesNeat Websites

www.aeswave.comNew scan tool for

Palm Pilots for

generic OBD IIBooks, tools,

equipment, meter

leads, etc.

Neat WebsitesNeat Websites

www.iatn.net (free)

Over 30,000 technicians onlineFee to join Become a sponsor ($10 per month), which

gives access to the data base

Neat WebsitesNeat Websites

www.transonline.com (free)

Automatic transmission siteValve body photosCheck-ball locations

Neat WebsitesNeat Websites

www.asetestprep.com (pay site)$29.95 for 30 daysAll eight ASE areas plus L1Guaranteed to pass the ASE test or your

money backCan be used for distance learning and/or a

credit course at your college