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High Altitude Study Report
Part 7

1985-1989 Imports
Hyundai, Mitsubishi, Plymouth
Feedback Carburetor System

Data Analysis

The data analysis of the Hyundai / Mitsubishi / Plymouth feedback carbureted system indicated the system could pass I/M 240 emissions test if operating as designed. Of the 13,539 Hyundai samples 147 passed final standards, while of the 3,329 Colts 46 passed final standards, and of 1,215 Mitsubishi samples 17 passed final standards on the initial test. This would seem to indicate the system has difficulty passing at final standards, but further analysis indicated the system would pass at Colorado’s potential final standards without modification.

Filters were applied to identify the vehicles that failed their first test, had multiple repair attempts, and passed the I/M 240 emissions test but would not have passed final standards (see note at bottom of page for final standards info). With these filters applied, 131 Hyundai, 19 Colts and 7 Mitsubishi were identified as marginal cars. Keep in mind that fast pass and second chance tests were filtered out to give a stable data sample. This reduces the number of qualifiers dramatically. These vehicle owners were contacted via the mail through the use of Colorado Department of Revenue (CDOR) records. These owners were offered free repairs to their vehicles if they would participate as study candidates. Of the 157 owners contacted, one responded to the offer.

The filters were re-applied to identify the vehicles that had failed the first test, were repaired, and passed the second test within final standards. 25 Hyundai and 3 Colts were identified as repaired clean. These vehicle owners were contacted via mail through the use of CDOR records. The owners were asked if we could contact the repair technician to determine what repairs were made and how the technician approached the repair. There was no response to this mailing.

Interviews

The interview process was carried out over the phone with responses listed in this section. Owners were interviewed about the experience and asked if we could contact the technician if applicable. Since there was a poor response to the mailing, interviews were conducted with CDOR personnel to determine the results of the high waiver rate.

Vehicles that failed the initial test, had multiple repairs, and passed but not within final standards:

The only response to the study had experienced trouble in repairing the vehicle to pass the I/M 240 emissions test during his last test effort. The vehicle was repaired by a technician whom he refused to identify. The repair included a tune up and carburetor adjustment. The successful repair included the addition of 10 cans of fuel de-icer to a nearly empty fuel tank. The results were a marginal pass with tremendous driveability problems. Upon inspection of the vehicle, it was determined the tune up was made by a mass merchandiser upon request by the vehicle owner. The responding vehicle owner was accepted as a study candidate.

Vehicles that failed the initial test, were repaired, and passed within final standards:

There were no responses to the mailing. Several successful shops were interviewed to determine how they approached the diagnosis and repair of these vehicles. Each of the 4 shops interviewed use an EDGE-type strategy and have a very good understanding of how this system operates. Their records show this system can be repaired to successfully pass Colorado I/M 240 final standards. The average cost of repairs made by the shops interviewed was $250.00. All shops had no problem repairing the vehicles in less than a working day. Typical problems included coolant temperature sensors, oxygen sensors, AIS system problems, and clogged catalytic converters. Technicians interviewed had attended both Colorado State University emissions classes and EDGE classes. They used a gas analyzer, lab scope, and DVOM to identify problems. CDOR personnel were interviewed to identify the most common problem with waived vehicles. Tim Barnett of CDOR commented that the coolant temperature sensor seems to be the most common problem area but that systems operating as designed seemed to pass with no problem.

Results:

After interviewing the technicians and customer, it was determined that the vehicles could most likely be repaired to pass the I/M 240 final standards. The vehicles in these samples included two versions of a similar system. The early system seemed easy to repair and the late system did not fail as often. The EDGE strategy was applied to the study candidates during the validation phase.

Recruitment

One of the candidates was recruited via the study mailing, one was acquired via a local shop aware of the study and one was referred by the Air Care Colorado Technical Assistance Program. The first candidate was a Plymouth Colt owned by a new Colorado resident and was referred by a local repair facility. The second candidate was a Mitsubishi Precis belonging to the sole responder to the study mailing. The third candidate was a Hyundai owned by a woman who was referred by Clarence Stevens of the Air Care Colorado Technical Assistance Program. All candidate owners were very satisfied with the results of the study and the repairs made to their vehicles. Each vehicle was returned to the owner clean and full of gas.

Validation

See the related documentation for further information on the diagnosis, repair and validation of the three Hyundai / Mitsubishi / Plymouth candidates. The EDGE strategy was applied to each candidate. Candidate #1 required a coolant temperature sensor, candidate #2 required a coolant temperature sensor and an AIS tube repair, while candidate #3 required an oxygen sensor and a carburetor replacement. The vehicles were validated using the EDGE strategy with each vehicle being returned to the I/M 240 testing lane for verification operating in fuel control. All vehicles had somewhat marginal catalysts indicating the potential for better results if the catalytic converters were replaced. We decided not to replace the marginal catalysts to better replicate the results of most in-field repairs.

Documentation Notes

Accompanying vehicle documentation and the technician guide for this group of vehicles are available in the printed version of this report, available from the Colorado Air Pollution Control Division, 303-692-3126. We plan to add the tech guides to this website as PDF files in the near future.

"Final standards" refers to U.S. EPA recommended final emissions standards. These can be found at the EPA website at www.epa.gov/oms/epg/techguid.htm. Click on the "6/96 Draft Revised IM240 Technical Guidance" item, and go to page 3. Note high altitude standards. You will need Acrobat Reader to view this PDF document. It is free from the Adobe website.

More Info

  Part 1: High Altitude Project Profile
  Part 2: Project Methodology
  Part 3: 1982-86 Chevrolet LDGT 5.0/5.7L; Non-Feedback Quadrajet
  Part 4: 1983-85 Ford LDGT 4.9L; EEC-IV Feedback Carburetor
  Part 5: 1984-85 GM/Jeep LDGT 2.8L; Non-Feedback Varijet
  Part 6: 1984-85 Low Altitude Honda Accord; Carburetor Feedback System
  Part 7: 1985-89 Imports: Hyundai, Mitsubishi, Plymouth; Feedback Carburetor System
  Part 8: 1983-87 Toyota Tercel; Computer Controlled Emissions

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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