1999 4-runner 6-cylinder. starts and then immediately dies. Any ideas?
I’d start by checking the idle air conrol (IAC) valve:
If you can keep the engine running by slightly stepping on the accelerator once the engine starts, there’s probably a problem with the IAC valve.
If stepping on the accelerator doesn’t prevent the engine from stalling, then there may be a problem with the Ignition Control Module.
ICM’s function in two modes, These are the start and run modes. When starting the engine, The ICM is in the start mode and allows full battery voltage to ignition coil. This insures there’s a hot enough spark when the engine is started cold and the fuel mixture is at it’s richest condition. Once the engine starts, and the ignition switch moves to the run position, the ICM goes into the run mode. The ICM then drops the voltage to the ignition coil. This is done because once the charging system comes on line the higher voltage would fry the ignition coil and the plug wires.
So the ICM may be functioning in the start mode, but failing in the run mode.