Bought a modified '87 GN 2 years ago with plans to do more upgrades over time. It ran fine for about a year, then a problem came up out of nowhere. Iin Feb '19, I was doing an easy 45 mph cruise after fueling up at a gas station. After 2 miles, the engine started missing very badly. A/F went rich: 10 to 1. Fuel pressure was ok = 38 psi. But the car wouldn't go faster than 30 mph. Barely got it home. Engine ran bad whether warmed up or cold (note: cold here in FL is 75+ degrees).
Drained and refilled the gas tank - twice. No difference. Upgraded to a new fuel pump, regulator & larger return line, set FP at 43 vac line off. No change. Tried swapping ignition module and coil pack. No change. Tried a different MAF. No change. Tried different MAP. No change. Tried different crank sensor. No change. Changed to a different ECM (& transferred TT chip). No change. Powerlogger is working: displays rpm, temp sensor and MAP readings. No trouble codes displayed on the Scanmaster. Pulled plugs - all 6 covered in thick black, wet deposits.
I parked the car and built an entirely new engine (forged parts & roller cam) - just completed. To break in rings, wanted to run engine for 10 minutes at 2600 rpm. After 6 minutes it missed, then missed more as time went on. Pulled plugs. Lots of black, wet carbon deposits - just like in '19. Exhaust spit out black soot. Bosch O2 sensor is new.
What other info do you need to figure this out?
TT alky chip & Motron 60 lb/hr injector combo
Powerlogger
Scanmaster 2.2
Bosch 13953 3 wire-narrow band O2
62 Precision turbo
Razor Alky Control
Front mount intercooler
212 Crane hydraulic roller cam
Fuel 93 octane gasoline
Innovate Wideband gauge
Autometer Fuel pressure gauge
Caspers knock gauge
Autometer boost/vacuum gauge
Autometer tachometer
Drained and refilled the gas tank - twice. No difference. Upgraded to a new fuel pump, regulator & larger return line, set FP at 43 vac line off. No change. Tried swapping ignition module and coil pack. No change. Tried a different MAF. No change. Tried different MAP. No change. Tried different crank sensor. No change. Changed to a different ECM (& transferred TT chip). No change. Powerlogger is working: displays rpm, temp sensor and MAP readings. No trouble codes displayed on the Scanmaster. Pulled plugs - all 6 covered in thick black, wet deposits.
I parked the car and built an entirely new engine (forged parts & roller cam) - just completed. To break in rings, wanted to run engine for 10 minutes at 2600 rpm. After 6 minutes it missed, then missed more as time went on. Pulled plugs. Lots of black, wet carbon deposits - just like in '19. Exhaust spit out black soot. Bosch O2 sensor is new.
What other info do you need to figure this out?
TT alky chip & Motron 60 lb/hr injector combo
Powerlogger
Scanmaster 2.2
Bosch 13953 3 wire-narrow band O2
62 Precision turbo
Razor Alky Control
Front mount intercooler
212 Crane hydraulic roller cam
Fuel 93 octane gasoline
Innovate Wideband gauge
Autometer Fuel pressure gauge
Caspers knock gauge
Autometer boost/vacuum gauge
Autometer tachometer