Q: I cleaned the ECM/PCM and now my car won't stay on

Whenever the ECM is disconnected the idle control settings the ECM has stored in memory will be cleared. The ECM will revert to the factory-new settings and since the engine now has high mileage and the need for adjustments to the idle will need to be relearned by the ECM. The idle will be erratic and possible stalling for a couple of days or more unless you go through the idle learn strategy.

If you start vehicle with no accessories on, let it idle in park for two minutes then turn on the AC and put on medium blower speeds and let it idle for two minutes. Then do the same thing in Drive without touching the gas pedal. Once this is done then your engine should run without stalling. If it continues to stall all the time then have a mechanic check the problem for you to see if the ECM is damaged or the engine needs work.