5.0 backfires - problem solved!

[chuzie]

This procedure assumes you have just completed a KOEO test.

KEY ON/ENGINE RUNNING (KOER) SELF-TEST
NOTE: If engine will not start, go to TEST A. If engine starts but
stalls while testing, go to DIAGNOSIS BY SYMPTOM TEST.
Code Output
1) Deactivate SELF-TEST (disconnect jumper wire). Start
engine and run it at 2000 RPM for 2 minutes to warm up HEGO sensor.
Turn engine off and wait 10 seconds
2) Start engine. Insert jumper to activate SELF-TEST. The
engine ID code will be displayed.
3) If a Dynamic Response code occurs, briefly accelerate
engine to wide open throttle (WOT). DO NOT depress throttle during
test unless a Dynamic Response code occurs. The KEY ON/ENGINE RUNNING
(KOER) SELF-TEST service codes will then be displayed. Observe and
record all codes.
NOTE: On the 5.0L SEFI engine a service code 98 may appear instead
of the engine ID code, indicating the need to obtain a code
11 for the KEY ON/ENGINE OFF (KOEO) SELF-TEST portion of the
QUICK TEST.