Bucking, jerking at 45-60 MPH under acceleration

A true case of low blinker fluid! Ha!

 

We have a 2004 with 340k. Started doing this stuttering thing again last Friday. Has had the transmission shudder since we got it with just under 200k and has not gotten any worse. Last time it stuttered, we had a cylinder 4 misfire so I did plugs and just that coil pack with an aftermarket one. Got the same cylinder 4 misfire afterward so I replaced all of the coil packs with OE Toyota parts and it went away. Fix only lasted about 6 months. Car is driven very hard (not by me) and loses some coolant as well. It's not in the oil, it doesn't smoke, and it runs well till now. Radiator was replaced a little over 2 years ago - was cracked at the neck. Not sure what to try next. We also have the catalytic converter code/O2 sensor code despite replacing that (drivers front cat and both sensors on that side) last year too. She likes driving it but it's starting to cost more to fix.