2007 Mazda 3 with 4cyl 2.3L motor FWD.
The problem is that when the engine is under load, even when barely accelerating at 10-15 mph, the engine is moving a lot. It's as if the engine is being thrown around inside the engine bay. It's not a light vibration. It's as if the engine is trying to come off the mounts.
Jacked the front of the car up and safely supported it on jack stands with the parking brake engaged. Put the car into drive, looked under it and saw the rear transmission mount moving significantly from left to right.
Went ahead and replaced both pieces that make up the rear mounting system as well as the driver side transmission mount and the engine mount on the passenger side while I was at it.
The only recent work done to the vehicle was an axle and a strut mount. I don't think either of these are the issue though. I inspected the entire front suspension for looseness and made sure wheels were bolted down tight. All good.
Took the car for a drive and still the same problem. Any suggestions or ideas on what could be the source of this issue? Could the crankshaft be unbalanced?
Thanks for the help!
Have you checked the engine mounts?
Yep l started in the OP that I replaced the mounts.
If you have a floor jack, put a piece of wood like a 2×4 between the oil pan and jack, then slowly jack up the motor. The car should rise as soon as the motor wants to go. If the motor itself rises, you have a broken motor mount. Crankshafts have harmonic balancers on the front of the engine to stabilize them. I've never really heard of one going bad, you would know if it is, the engine would want to tear itself apart.
Yep, checked the mounts before I replaced them. I can double check the balancer. Would it have any wobbling motion that is visible if it were bad?