recently i bought a 1988 RX7 convertible. Great car. Buddy borrowed it and blew the motor, a 13b. I changed it out with another 13b and now at around 3500rpm, the engine begins to shake. It does this regardless if the clutch is in gear or if I am driving down the road. I am not a gear head and it seems that all the mechanics around here think a rotary means the pistons turn sideways. Any help?

 

Do not ever, ever, EVER take your car to these "mechanics" again. You will be doing yourself a huge favor.



Anyways, onto your problem. Possibly either a motor mount problem, or a balancing issue. You say it does it even with the clutch in? I would say something is out of balance - when you changed the engine, did you screw with the counter weights, or did the flywheel get damaged in anyway?

 

More importantly, was the flywheel ever removed and put back on?

 

The flywheel was resurfaced and a new clutch put in. The engine was never opened up. It was just swapped.

 

I don't know, but I don't believe any counter weights were touched. And when a MECH said sideways, I said thanks and DID walk away.

 

Check all the Mounts..Engine mounts,and the Transmission mounts..I had a Broken Engine mount..it sounds the Same as what you are Experiencing.Maybe a mount never got Tightened down?