Here is a problem which I have seen mentioned in more than a few forums but nobody has been able to provide a definitive answer. I have a ’90 Toyota 4Runner with a 22RE fuel injected engine having 176000 miles. Cold start is fine and idles normally. However, after it has warmed up (hot soak) it will still start right up but will run rough and die unless I give it gas to 2000 RPM and hold it there for 5 seconds or so. Then it will return and hold normal idle. There is also a strong smell of gas. Basically it floods. I have replaced the distributor cap, rotor, spark plugs and distributor itself then ran two cans for fuel injector cleaner through it. I also disconnected the Cold Start Injector Timer Switch thinking that was the problem. Nothing had an effect. Compression is a little low in all cylinders (expected with this mileage) but nothing drastic. One last thing I don’t know if it deserves mentioning. The muffler has something broken inside because it rattles loudly. I have not gotten to that yet.
The problem might be caused from a leaking fuel pressure regulator.
Turn the ignition switch on and off a half dozen times to cycle the fuel pump that many times. Remove the vacuum hose from the fuel pressure regulator. If gas leaks out of the vacuum hose replace the regulator.
Problem solved!!! Broke down and took it back to the dealer. They must be under new management because they were friendly, helpful and even knock 15% off the bill. Anyway it was a faulty Coolant Temp. Sensor. It was causing the engine to think it was always cold thus flooding it with gas when it didn’t need to. The whole affair (two mechanics and my efforts) only cost a grand. Oh well. Got a new distributor, new plugs, new rotor, new coil, new cap, new temp. sensor and the throttle assembly cleaned.