Does anybody have any insight as to why this may be happening?

My car stalled and refused to turn on one day while I was at a light, so I had it towed to my mechanic (whom I trust and has been doing work on our family vehicles for years). After running diagnostic tests, it came up with a code for which the advisory was to replace the ECM (I later learned this is an issue with 2005 to 2007 Corollas). This was done and I drove away seemingly without problems. The next day however, I stalled again at a stoplight. I brought it back to my mechanic, who again ran diagnostics, and said that given the codes they were given, the first solution was to replace the ECM, and if that was unsuccessful, it should be followed by checking the throttle body (which was in disrepair). The throttle body was replaced and I drove it back home again without any problems. The following morning (this morning) I was driving into work, and every time I was at a stop light the RPM would drop below 1000, the car would vibrate, it would shoot back up again above 1000, slowly lower down towards 1000, only to repeat the rapid drop and rise again in rpm until the light turned and I was able to start driving again. I am pretty unnerved, because that same kind of erratic shake happened just before my vehicle stalled the second time.

Any thoughts? Has anybody else experienced this? Please advise. They checked everything else and didn't see anything that would be indicative of a problem.

I've been reading around on forums, and someone indicated that it may take a bit of driving for the car to relearn. I'm just concerned though because the erratic shake is eerily similar to what happened before it stalled on one of those occasions.

  • Welcome to Motor Vehicle Maintenance & Repair. I'm guessing this is an automatic? I don't have an answer for you now, but if it makes you feel better, chances are, that erratic shake is a completely normal phenomenon for combustion engines when they reach very low RPMs (500 or less), particularly 4 cylinder engines. It's caused by the gap in between each combustion (you actually get negative torque during each cycle!), and it's normally masked at regular RPMs by bushings, chassis compliance, etc. So don't worry, most likely nothing bad is going to happen to your car. Jan 18 '19 at 15:01

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