I have a 1994 Toyota 4Runner 3VZ-E (V6) SR5 with 192K. Recently, it started having problems idling (cold or warm). Symptoms are loping idle from ~200rpm - 1000rpm. Problem comes and goes and does not seem related to the engine temperature. Other than that, the truck runs very well with a smooth acceleration and gas mileage in the low-mid 20s (remarkable for a 4Runner).
Jumping TE1/E1 on the diagnostic connector the ECM shows no codes whatsoever (continuous rapid flashes). I have replaced the the cap/rotor, ignitor, o2 sensor, scoped the MAF (called a VAF by Toyota), scoped the TPS (Throttle Position Sensor), checked the tension on the throttle cable, checked for loose or damaged vacuum lines, and completely cleaned the intake, all intake hoses to the throttle-body, and the throttle-body itself. I have also tried fuel system cleaners and water removers for the last 3 tankfuls with no change whatsoever to the symptoms.
Everything checks out but the problem persists. I have also taken it to 2 ASE-certified master mechanics and they are similarly stumped. So, my suspicion is this is still electrical, but I don’t know what else to check or replace (I have considered replacing the entire throttle-body). Also, in what is possibly a red-herring, these problems started immediately after taking it through a high-pressure automatic car wash. The attendant apparently left the vehicle idling during the wash cycle.
The vehicle is definitely drivable, but the problem worries me as this vehicle is my 9-month pregnant wife’s only transportation to the hospital at the moment.