 Air Care News
April 1998
High altitude
study identifies repairs for problem vehicles
by Chris Chesney
Repair technicians know that some vehicles have a harder
time passing the I/M 240 than others. Despite our best efforts, some vehicles repeatedly fail.
Why? Often, the answer is that vehicles were not designed for use at our altitude. Others need
to be repaired to operate as designed.
A recent study of six hard-to-repair vehicle families has helped
identify effective repair strategies and provide tips on diagnosis and repair that should help you
fix tough I/M 240 failures.
Denver's mile-high altitude creates significant
challenges for repair technicians in the enhanced inspection and maintenance area.
The six families studied included four feedback-type families
(1984-85 low-altitude-certified Honda Accords, 1984-89 Mitsubishi/Hyundai/Dodge 1.5L feedback
carbureted systems, 1983-87 Toyota Tercels, and 1983-85 Ford 4.9L light-duty trucks) and
two non-feedback type families (1984-85 GM/Jeep 2.8L non- feedback S10s, Cherokees and
1982-86 GM 5.0/5.7L light-duty trucks).
Data provided by the Colorado Department of Public Health and
Environment showed that the four feedback families should pass if operating as designed. The two
non-feedback families may require system modifications.
Vehicle owners and repair technicians were interviewed to identify
successful repair strategies. At least three vehicles from each group participated
in the study. All had failed the I/M 240.
Each vehicle was safety inspected, refueled with test
fuel and taken to a test lane for five I/M 240 tests. Each was treated like a regular test,
right down to getting in line.
After the baseline tests, each vehicle was diagnosed and repaired
according to the identified repair strategy. Once repairs were made, each vehicle
was returned to the same testing lane and five more I/M 240 tests were
completed. Also, if the vehicle was modified from its normal design, it was taken to
a lab and a Federal Test Procedure (FTP) was performed.
All vehicles later passed the I/M 240 test with flying colors,
showing significant improvements in drivability and fuel economy.
The High Altitude Study confirmed that returning feed-back-controlled
vehicles to designed operation specifications results in greatly-improved I/M 240 test. The non-feedback,
low-altitude vehicles require some modifications for high altitude operation to maintain catalytic
converter integrity.
The State of Colorado soon will offer six one-night classes
that will feature each vehicle examined.
For information on any of the vehicles in the study, contact Chris
Chesney at 425-9608, ext. 4. Check out future editions of Air Care News to
learn when you can enroll in the courses once they become available.
Want to read the study itself? You can view the
study report, along with the reports on the six vehicle groupings.
Chris Chesney is the owner of Diagnostic
Technician Education Consultants (DTEC), 5497 S. Danube Way, Aurora, CO 80015. He can be reached at
720-870-6761 or via email at chesneydtec@cs.com. Chris has
trained hundreds of technicians in I/M 240 diagnosis and repair.
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Many repair technicians have struggled to
repair 1984-85 low-altitude Honda Accords. These vehicles have high initial I/M 240
failure rates, and often fail repeatedly after repairs.
The High Altitude Study identified some problems and offers
information that will help you fix them right the first time.
Early in the Air Care Colorado program, technicians either
replaced the carburetor top or assembly with a high altitude model and installed a high altitude
compensator, or drilled the primary air bleed to equate the air flow of the high altitude
compensator. The first repair was too costly and the second was deemed unacceptable
by the manufacturer because the vehicle would no longer be suitable for low-altitude
use. The air jet could not be returned to normal size.
The study identified alternative repair strategies, using
an EDGE-type (Emissions Diagnostic Graduate Education -- a tech training curriculum for emissions
repairs) approach that ensures that systems would operate as originally designed despite the
challenges of our rarified atmosphere.
Four problem Hondas in the study were used, including a 1985
Accord with 94,280 miles that had failed several I/M 240 tests. At a State Technical Center, it
checked out with an average output of 74 g/mi carbon monoxide (CO), 1.8 g/mi hydrocarbons (HC),
and 0.2 g/mi oxides of nitrogen (NOx). The vehicle had been tuned and the carburetor adjusted with
no success.
The owner complained about a clutch problem. To ensure accurate
results, that problem was addressed before proceeding with the baseline test. The clutch was
slipping slightly and was replaced. Surprisingly, the vehicle passed three tests at 23.0 g/mi
CO, 0.7 G/mi HC, and 0.3 g/mi NOx after the clutch repair!
After using the EDGE diagnostic strategy, the oxygen sensor
was found to be lazy and was replaced. Fuel control returned to normal, under load, while driving
down the road. The vehicle was tested again and passed with even lower emissions
levels of 15.0 g/mi CO, 0.4 g/mi HC, and 0.4 g/mi NOx.
The other Hondas were brought in. Along with the clutch
and oxygen sensor, identified problems included cracked vacuum lines, clogged vacuum passages,
missing grounds left loose during clutch repairs, and vacuum switch failures. All
seemed to have been either damaged during clutch repairs or not maintained very well.
Interviews with technicians revealed many technicians
did not fully understand the repairs required of the Honda feedback carburetor system and how they
affect emissions. As a result of the study, a one-night course has been developed to
teach technicians how these systems operate and how to effectively diagnose and repair
them to pass the I/M 240 test. If repaired properly, these systems can and will pass.
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A two-year study conducted by the Colorado Department of Public
Health and Environment has concluded that remote sensing can be an effective part of air pollution
reduction strategies.
Patti Shwayder, the department's executive director, said,
"The results of the study in Greeley confirmed that remote sensing can be used effectively to
identify low-polluting or clean vehicles."
A bill in the Colorado Legislature would give local air pollution
planning authorities in basic test areas the option of making remote sensing a regular
part of their vehicle emission reduction strategies.
The remote sensing equipment would be used as a clean screening
tool to exempt up to 50 percent of the vehicles registered in a given basic emissions test area
from undergoing an annual or biennial tailpipe test. If a vehicle is shown to be
clean by the remote sensing equipment two times in a given registration period, that
vehicle would be exempt from the annual or biennial test.
The legislation also calls for a year-long study in Denver to
study the effectiveness of a clean-screening program in a large metropolitan area.
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Please excuse Lee Peterson if he seems a bit distracted these
days. Getting married can do that to a guy.
Peterson, who was married March 21, hasn't allowed his new
status to affect his work though. The proof? The best individual technician repair effectiveness
index (REI) in the business.
Of 467 individual repair technicians in the enhanced program
area ranked for their effectiveness at correctly diagnosing and repairing emissions-related failures
Peterson ranks first.
He credits his lofty status to "a lot of
perseverance."
"I'm interested in it. I read everything I can get my
hands on. I go to Tech Nights and study a lot," Peterson said. "Because I own the
shop, I can afford to spend more time on the cars than a guy who works for someone else."
Peterson is the owner/operator of Precision Auto Repair, Inc.
in Longmont. He's been his own boss since he was 21, and has had the shop at 1118 Kimbark Street for
15 years. He's made a career out of an interest that began when he rebuilt engines as a teenager with
his father, a retired school administrator.
"It kind of happened naturally," Peterson said.
"It has been the right fit. I really like doing it."
Since the I/M 240 began in 1995, Peterson has seen more
first-time customers who are seeking emissions-related repairs. Although still a small percentage of
his business, effective emissions repairs can go a long way toward building a trust that will bring
customers back to his ship for other work.
Peterson agreed that the REI system of ranking repair shops and
technicians is important, although he feels the system needs to be improved and refined. He sympathizes
with the owners of older vehicles that need costly repairs that still may not be enough to pass an
enhanced test.
"The REI has some problems, but I think it is important,"
he said. "I understand the incentive to get cars to pass. What I like best about I/M 240 is that
every car is capable of passing."
And Lee Peterson is currently the best at making that happen.
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