So everything on my truck seems to be fine for a while until recently. When I start going in 1st and occasionally when I shift to 2nd the truck jerks almost as if loosing all power and suddenly getting it back. It only does this occasionally and lately the check engine light came on. Went to a checker and ran the OBD1 test that came back with a DTC90 code. The only definition of the code that I get says "SERIES FUEL/AIR INJECTION CODES ON VEHICLES WITH DUAL OXYGEN SENSORS REFER TO THE LEFT OR FRONT SENSOR. EXCEPT: 1984-1988 3.8L ENGINES: RIGHT SENSOR" This was a stored code in the memory. Both other tests came back clean with no codes. Could this be the cause of my problem and if so or if not how do I fix this?

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1988 XLT
Standard Cab