Connected the scope over the weekend to read signals from reference and speed sensors.
Signal checked out OK and strong, so this means the problem is elsewhere.
Seems like it's hands down for me at my underground parking and the car will have to wait for the warm season, when I will be able to send it to the the aircooled specialist in Poland.
I entered this prompt below to Gemini, and it doesn't give me many suggestions what I could do at home.
Code:
My Porsche 911 3.2 1985 has a rough idle problem, misfires, smell of unburned fuel. For diagnostics, here's what is known and what steps were already taken:
- engine fully rebuilt in May 2025, 5000 km done since then;
- injectors have been tested for function and proper spray pattern during rebuild;
- mileage for first 5000km after rebuild was spotless. The power hesitation at high RPM was spotted, folowed by a slight misfire (popping) and later by erratic idle;
- fuel pressure regulator (FPR) and diaphragm damper were replaced, fuel pressures now checks according to spec;
- compression test is OK, 11 BAR across all 6 cylinders on cold engine;
- leakdown test of a cold engine is OK;
- cylinder Head Temperature (CHT) sensor resistance is OK;
- plug wires connected in correct order;
- disconnecting O2 sensor brought no effect;
- Air Flow Meter (AFM) has been refurbished during rebuild, contact track replaced;
- Intake air temperature sensor resistance OK;
- to check for DME faults it was swapped to a another known good unit with no effect;
- FULL THROTTLE and IDLE switches tested;
- no vaccuum leaks detected with a smoke test;
- flywheel speed sensor and reference TDC sensors are OK showing correct resistances and generating correct sinewaves;
- ignition coil resistance has been checked, is OK, both primary and secondary coils;
- spark plugs and spark plug wires replaced to new during engine rebuild;
- ignition cap and rotor were not replaced and have around 30000 km on them;
- GROUND connections checked and cleaned;
- valve clearance has not been adjusted since the rebuild;
What are possible next steps for diagnostics?
As it's a simple shot, I just ordered a new distributor car and rotor, as they haven't been replaced after the rebuild.