P0135 Mercury Tracer 1998 2.0 LS 124K miles

Problems Unresolved:
1. check engine lite on--scan shows P0135
replaced with Ford upstream 02 sensor
lite persists
2. idle mostly rough; will die occasionally: surges
fuel pump checked OK
new fuel filters (2)
injectors surviced OK
vacuum leaks none

Additional Question:
Does O2 sensor P0135 problem cause idle, stalling problem?

Thanks for any help, suggestions (I read "related DTC discussions).

Nicolai

re above, wiring checked again for shorts: found water damage on wiring inside car near PCM; replaced PCM: runs better for 2 days but still shows P0135; checked Ford Dealer: "rarely does 02 sensor fail" and "you probably will have to replace wiring, none available here at parts" any suggestions? Nicolai

before you purchased the new FORD OEM o2 sensor.... did you check the heater portion of sensor for 12v- and check fuses?

Good thing you checked the fuel pressure - what was the pressure (psi) ?

Hello kev2, all fuses are OK; don't remember fuel pressure reading number but was up to par; the P0135 reading: FUEL SYSTEM 1=CL FUEL SYSTEM2=NA CALC LOAD (%)=33.7 ECT(F)=192 STFT BI(%)=-4.7 HAVE NOT CHECKED HEATER SENSOR FOR 12V. NICOLAI

To finish off...first of all, is this car of mine actually ...a female?!! Couldn't make up her (its) mind? Replaced the PCM. Then, the heater core blew out; by-passed the core; low and behold, the check engine light finally went out; the cooling fan wouldn't go on--then it did. (did the water short out the wires in the harness leading to PCM?) So now, with winter coming, $ for new core? Or new used car? Thanks for comments. N.