2.3L ('83-'97) Idles rough, won't stay running , bogs on acceleration


New member
Feb 12, 2020
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Fort Bragg, Ca.
Vehicle Year
Make / Model
Ranger xlt
93 xlt 2.3l 130kmiles
First KOEO codes: 121= throttle position sensor out of self test range or
throttle position voltage inconsistent with MAF sensor. Double checked for any vacuum leaks and replaced TPS. No change. Test voltages to MAF sensor, check out o.k. but cannot run proper MAF test or KOER codes due to engine won't stay running. Replaced MAF sensor. No change. Engine runs fine with MAF unplugged due to stored baseline data. Cleared codes re test KOEO and
pull these codes: 157= MAF below minimum voltage
158= MAF above max voltage
543= Fuel pump circuit open, battery to PCM
The only thing between the battery and the PCM is the fuse (ok) the inertia switch (ok) and the fuel pump relay, so I replaced the relay. No change.
I would not suspect an ignition or a fuel pump problem since it runs fine with
with MAF disconnected. My Haynes manual is pretty useless when it comes to individual component tests. My next guess would be testing the PCM or the electrical to the EGR ( diaphragm holds vacuum). Any help with test procedure info. or suggestions would be much appreciated. I usually won't replace a part unless I get a solid diagnostic on the problem , however this one is taking me on quite a ride and I need my truck back.
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