Date: 201912
Local time of day: 1201-1800
Location: NCT.TRACON, CA
Flight conditions: Mixed
Weather elements / visibility: Haze / Smoke; 10
Light: Dusk
Aircraft: Skylane 182/RG Turbo Skylane/RG
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Initial Approach
Airspace: Class E ZOA
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Private; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Took Evasive Action; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Procedure; Weather
Primary problem: Procedure

Narrative: An unidentified aircraft passed between me and the ground; at the FAF (Final Approach Fix) with me less than 1;500 ft. AGL; requiring an urgent climb and cancelling of approach clearance. Also; during the event I deviated approximately 250 ft. low in altitude.Details: I was on IFR flight plan; being vectored to ILS Runway 25R. Weather was irregular scud; with a ground haze + scattered layer with tops ~3;000 ft. MSL. Visibility above was unrestricted; but low sun angle; with sun approximately 30 degree left of approach course; severely restricted forward (especially downward) visibility.I was on vector 150 deg. When I estimated to be 1-2 nm from intercept; I queried Controller if I was going to be vectored across FAC (due to 105 deg intercept angle; and still being high at 900 ft. above intercept altitude). Controller immediately responded with vector 240 deg; immediately updated to 250 deg; and clearance for the approach. While in this turn I crossed the LOC; so I steepened and continued past LOC heading; while initiating descent to GS intercept altitude.While steadying up on LOC at approximately 1-2 nm from FAF; controller issued a traffic advisory; which I did not entirely copy: however I did get 'crossing left to right' and 'will merge at ZZZZZ'. I began looking out of the cockpit; but although I had ground contact; directly into the sun and scud visibility was very poor.When I looked back in the cockpit I discovered I was descending through 200 ft. below intercept altitude; and immediately began to climb. Shortly after the controller issued a 'Cancel approach clearance' and 'Climb immediately'.After landing; my right seat passenger informed me she saw the target come out the right side; 'directly beneath' us. At that point I estimate we were approximately 1;400 ft. AGL; however there are a large number of obstacles (windmills) in that area; heights approximately 300 ft. Therefore I believe vertical separation was perhaps 500 ft. or less.My surmise is that the aircraft was trying to cross the 1;700 ft. pass while staying under the scud layer at (or less than) 3;000 ft. MSL.My undershoot on altitude was due to still being in descent close to FAF; and distraction while searching outside the cockpit in limited visibility for the close target.




Synopsis: Pilot reported a traffic conflict on an instrument approach that resulted in a missed approach.