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High Altitude Study Report
Part 4

1983-1985 Ford LDGT 4.9L
EEC-IV Feedback Carburetor

Data Analysis

The data analysis of the Ford 4.9L feedback carbureted system indicated the system could be repaired to pass I/M 240 final standards. Of the 5,566 1983/85 vehicles in the data sample, 664 passed within final standards on their initial test. This indicated the ability of this system to pass at or within final standards.

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, 38 models were identified as marginal. The vehicle owners were contacted via 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 38 owners contacted, none responded.

The filters were re-applied to identify the vehicles that had failed the first test, were repaired, and passed the second test below final standards. Forty-four vehicles were identified. The owners of these vehicles 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. Only two owners responded, but were very helpful and cooperative.

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. In all but one case, the owner had repairs made by a technician.

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

Since no customers responded to the mailing, DTEC contacted several Master Technicians in the area. Each technician identified the most likely causes of failure as loose or deteriorated carburetors, air injection systems, improperly assembled replacement carburetors, and basic EEC system failures. All of the technicians interviewed had attended EDGE training. Average repair costs were $315.00. Equipment used included a gas analyzer, labscope, and DVOM. Understanding of the specific operating strategies was viewed by the technicians as the most important skill required to properly repair these vehicles to pass the IM240 test.

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

Of the two vehicles identified as repaired properly, one required an oxygen sensor, one required a catalytic converter, and both required disassembly of the carburetor to overhaul or repair internal problems or misassembly. Independent garages performed the repairs. The average time to repair the vehicles was less than one working day at an average cost of $359.00. The technicians all had attended various emissions classes including Colorado State University and EDGE. Each technician used a gas analyzer and a labscope or DVOM using an EDGE type diagnostic strategy.

Results:

After interviewing the technicians and customers, it was determined the system could pass the I/M 240 if operating as designed. During the validation phase of the study, the EDGE diagnostic strategy would be applied to the study candidates.

Recruitment

All of the study candidates were referred by the State Technical Centers. A young man who attempts to do his own work owned candidate vehicle #1. A homemaker that had been issued a waiver owned candidate vehicle #2. Candidate vehicle #3 was owned a retired man who had loaned the truck to his grandson and was returning it to service as a tow vehicle. All were willing to participate and 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 Ford candidates. Vehicle #1 required replacing the catalytic converter with the proper part as well as replacing the upstream check valve for the air injection system. It also needed a carburetor overhaul to correct the loose throttle body and required a new oxygen sensor. The vehicle was also carbon cleaned. During the fourth validation test the vehicle suffered a blown head gasket between cylinders number 1 and 2. The vehicle owner was aware of potential engine damage prior to the study. He gladly took delivery of the vehicle and performed the repairs to the head gasket himself. Vehicle #2 needed an intake manifold gasket, mixture control solenoid and a total exhaust system. The carburetor also required disassembly and correction of the previous overhaul. This was a recently waived vehicle. Vehicle #3 required a new EEC relay. The original relay was missing. The carburetor also had recently been overhauled and required disassembly and correction of the previous overhaul. The results indicate repairing the system to operate as designed will result in a successful repair.

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 atchesneydtec@cs.com. Chris has trained hundreds of technicians in I/M 240 diagnosis and repair.

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