Camry started acting up out of nowhere. Running rough, idle hunting, overshooting idle and nearly stalling when letting off throttle, misfires, sweet exhaust smell (like carb cleaner/bad gas smell not coolant; eg rich mixture through a 18 yr old cat smell). After messing with distributor/ignition coil assembly and not finding any problems, I started looking at critical ECU inputs. Crank/cam position sensors are in the distributor so I moved on to MAP sensor. Unplugged it, no change.
As I fiddled with the sensor I noticed the engine behavior changing, until I finally happened to feel and hear a vacuum leak through the hose that connects it to the manifold. It's a short rubber hose that makes the final 90 degree bend from the hard vacuum line to the MAP mounted on the firewall, and the outside bend side of the hose had worn and cut against the MAP nipple in the last 18 years + bad motor mounts at one point. Three inches of rubber hose that I already had on hand and it runs good as new again. Still stumbling on sudden throttle opening and heavy load but it's resolving itself as the ECU recovers and pulls back fuel trim and the plugs and O2 sensors "dry out". As of last night after second day of driving and running through various acceleration/load cycles on my commute, it's back to normal.
It's a 1995. Everything is relatively modern SEFI paradigm with the minimum of everything you WANT to be solid state, but still basic and simple in that it doesn't obfuscate you from the basics of the 100 year old ICE at it's core. It's pre OBD-II so requires old fashioned troubleshooting still instead of just having a computer tell you what's wrong immediately.
It's the perfect learning platform IMO, the pinnacle of EFI perfection post 80's rats nests but pre 2000s complexity and obfuscation where you can't work on your own car without being a programmer or having $10,000 in scopes and analyzers. It's like the simplest EFI engine there is (Toyota 2.2L 5SFE).