i pulled these codes on my 90 sc and need some help pinpointing my problem
koeo codes
83 high speed fan failure
85 canister purge circuit failure
koer codes
25 knock sensor
72 insufficient mass airflow change
73 insufficient tp sensor output
74 brake on off switch fault
please help on where to go next
high speed fan: With the engine running turn on the A/C. The high speed fan should come on automatically. if it does, there is an issue beteen the IRCM and the PCM as far as the signal for the fan being activated. If it does not come on, check power at the fan plug. Power=bad motor. No power=trace the wiring to find the problem, probably a bad IRCM.
Canister purge: yuck, emissions. Probably a dead or plugged solenoid, or a vacuum leak.
Knock sensor: probably a dead sensor, possibly a break in the line to the PCM. Ask a dealer for pointers or check out fordcds.com for shop manual downloads.
MAF and TP sensor codes: often related. Try cleaning the MAF sensor wire very carefully with windex and a q-tip. And/or replace the TP sensor, they're cheap.
BOO switch: if you didn't specifically perform this test while pulling codes that code will always show, even if no problem. If you have brake lights, it's OK.
Also check your O2 sensors. I've had problems with 3.8's throwing wierd unrelated codes and running pig rich when the O2's start to go. If they have more than 70-80k miles, it wouldn't hurt to replace them anyway.
Hope this helps.