- Preliminary Information

This section is used to find the correct test procedure for a given symptom. The symptoms and actions in this section are Emission related only. Refer to Fuel Injection and Computerized Engine Controls for complete Diagnosis By Symptom for Fuel, Ignition, Computerized Engine Controls and Emissions. Always use the Flow of Diagnosis for proper testing sequence. Verify the correct system application to ensure that the vehicle has the given component(s).


***UPDATED BY TSB #91-57-6E DATED AUGUST 1990

A satisfactory exhaust emissions test includes making sure the vehicles engine and emission control systems are fully warmed up just prior to conducting the test. For example, although the engine coolant temperature reads normal the catalytic converter may not fully be warmed up. This may cause exhaust gas readings to be artificially high. Therefore if the vehicle has been sitting for several minutes idling or has been turned off the catalytic converter may not be up to operating temperature. To bring the catalytic converter up to operating temperature drive the vehicle a few miles prior to measuring the tailpipe emissions. An alternate method that can be used is to run the engine at 2500 rpm for three minutes with the transmission in park or neutral.


Before proceding to the appropriate symptom perform the following inspection:
NOTE: It is essential that the vehicle has been properly warmed up and is at operating temperature (except when attempting to diagnosis a cold driveability problem). The catalytic converter and feedback systems will not function as designed if this is not achieved. Failure to do so will result in inaccurate test results.

VISUALLY CHECK:
1 Vacuum hoses for splits, kinks and proper routing.
2 Ignition wires for cracking, hardness and proper connections at both the distributor and spark plugs.
3 All wiring for proper connections, pinches and cuts.
4 Harnesses (EST,ESC, etc...) for proper routing.