Well dammit. A couple of weekends ago I finally got my ‘82 Alfa GTV6 slapped back together. Took her out for a quick spin a week ago Sunday just to make sure everything still worked. Aside from the clutch plates being locked together (back end on jack stands, start in first gear, alternate brake and gas, it’ll come free) she was amazing. Full drift in 1st gear at 20 MPH, singing the loveliest song.
I got into fine tuning the Bosch L-Jet ignition this past Saturday since the engine had a full complement of new vacuum hoses, fittings, a few bits here and there. Got to the O2 sensor, last issue on my list, and it was reading high. The single-wire sensore should output about .45 volts, fully heated. I was getting .7 to .8 after idling for 15 minutes with 60 seconds of 50% throttle. The ECU should have been out of the startup fuel map by then, and I’m pretty sure it was because the reading is static when the O2 sensore is in closed loop but begins fluctuating somewhat wildly once the output signal starts feeding the mixture.
So I started by testing the coolant temperature sensor, which could prevent the car from reaching full operating temprature. Good reading. I’d also just cleaned the probe when I rebuilt the thermostat. Next was fully opening the idle bypass valve in the AFM module, letting in unmetered air, and loosening the AFM flap spring to factory setting (it’s common to tighten it, thus enriching the mixture to get faster throttle response). Got output voltage down to .65-.7. Still too high.
So, possible culprits? All of my plugs are sooty but the #1 plug was also wet. A stuck injector would explain it. I pulled the plenum, fuel rail and injectors. A couple of the injector o-rings, which are only a couple of years old, were cracked. Also possible problems. I’m taking the injectors to a local shop for flow testing tomorrow, with new injector seals on their way, as well as a new Bosch O2 sensor and coolant temp sensor. Why not.
I wonder if converting to a 3-wire (self heating) O2 sensor might help stabilize things though? Alfa switched to a 3-wire design in .85, I think. It would just need 12v and a ground, both of which are right there on the firewall. Otherwise stoich is stoich, right?
Also checking wiring, much of which is new.
If you ever wanted an Alfa, this is what it’s like. You get 15 minutes of driving for every 15 hours of work. I think an SR71 is more efficient in that regard!