Air Care News
January 1997

Difficult Diagnosis? Here are Some Tips

As part of an ongoing focus, Air Care News has included below some helpful hints on vehicles and engine engine families that technicians have identified as hard to diagnose. A thorough diagnosis according to recommended manufacturers' procedures is always suggested to ensure a successful repair and or emissions inspection; however, the checklists below highlight some trouble spots.

fail rate graph

Hyundai/Mitsubishi/Colt, Feedback, Carbureted

M/C solenoid
--check aftermarket sources
--solenoid O rings
EGR system
O₂ sensor
Temperature sensor
HAC valve
Jetting
--air bleeds
--throttle switches
--Sec air valve
--recalls
Plugged catalytic converter
Cracked exhaust manifold
Springs
Air bleed inlet filter

1985 Honda Accord

Carburetor calibration
Watch for low altitude certification
Verify speed switch
Air temperature sensor

Nissan Sentra Feedback Carburetor

M/C solenoid
--P/N 16197-61A03 Availability? Interchangability?
Catalyst
Sensor inputs
Grounds

5.0L Ford Early Feedback

O₂ reference grounds
Temperature sensors
TPS
EGR vent

EBCV Toyota/Chevy Nova

VACUUM!
--quality/routing
--check for obstructions
Air bleed control valve/wiring
Throttle switch
HAC valve
Carburetor function
Air bleed inlet filter

Adapted from an article by Brian K. Manley in the August 1996 issue of AutoInc. Magazine. Printed in Air Care News with permission.

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Fast Pass Q & A

Q: What does a fast pass mean during an I/M 240 test and inspection?

A: Fast pass means that a vehicle has been identified as the "cleanest of the clean" vehicles. By looking at the emissions characteristics of a vehicle as the I/M 240 treadmill test progresses, the computer can determine that a vehicle is so clean, the test does not need to be completed.

Q: What is the purpose of a fast pass option during an emissions test?

A: The fast pass is designed to reduce the time taken to perform test procedure, thereby creating a testing network that is smaller and more efficient. It is anticipated that the fast pass option will reduce the overall cost of operating the inspection and maintenance program while increasing convenience for the motorist.

Q: When will a fast pass be determined during an I/M 240 test?

A: Any time between 31 seconds and 239 seconds into the 240-second test. The current network average for a fast pass is 80 seconds.

Q: Does a fast pass test provide the same information as a full cycle test?

A: A fast pass provides equivalent information. Initially, a fast pass did not print detailed information on levels of pollutants. However, motorists were interested in comparing results from past tests (either I/M 240 or older idle results). Repair technicians wanted to know how effectively they had repaired vehicles. In response, the software was modified to project full cycle emissions results.

Q: Is fast pass always an option, regardless of when or where the test is performed?

A: All centralized Air Care Colorado testing centers in the Denver metro area are equipped for fast pass tests. However, it is not always available. One reason is that, to provide valuable statistics for assessing the overall effectiveness of the I/M 240 testing process, complete data from full cycle tests are needed. As a general policy, though, fast pass is available to the motorist.