Possible Causes & Corrections:

Ensure park/neutral switch is properly adjusted.
Check TCC for proper operation.
Check for restricted exhaust system.
Check for kinked or leaking vacuum lines.
Ensure initial ignition timing is properly set.
Using Spark Tester (ST-125), check for adequate spark output.
Remove spark plugs, and check for wet/fouled spark plugs, cracks in porcelain, improper gap, burned electrodes or heavy carbon deposits. Check distributor cap, rotor and spark plug wires.
Check ESC system for proper operation.
Check in-line fuel filter. Replace if dirty or clogged.
Check fuel for water contamination.
Ensure fuel system pressure is correct at all engine speeds.
If emission test shows excessive CO and HC emissions and vehicle emits odor, check all systems and components which could cause engine to run rich.
If emission test shows excessive NOx emissions, check all systems and components which could cause engine to run lean or too hot.
Check canister purge system for proper operation.
Check for an intermittent EGR system problem.
Check Oxygen Sensor (O2S) for lead or RTV sealant contamination. Such contamination causes a false high voltage signal to PCM, which responds by leaning air/fuel ratio.
Check PCM grounds. Ensure they are clean, tight and properly located.
Check charging system output. Repair if output is less than 9 volts or greater than 16 volts.
Check A/C for excessive charge.