97 Civic w/ DI6Y7 engine shakes badly at loaded idle

Only a few days ago and following a loose harmonic balancer spinning on
the crank and grinding off the spline teeth of both parts, a salvaged
motor from a 94 Civic was installed by a local garage. The folks that
sold us the engine ($700 w tax) said it had 94K miles on it. They also
said it had very good compression in all cylinders. The garage staff
said the engine looked very clean inside and out. Recommended parts
were replaced. i.e. Timing belt, main seal, valve gasket, water pump,
clutch (flywheel surfaced), thermostat, etc. Engine sound nice and
smooth. Seems to have normal horse power (according to son who drives
it). The salvaged engine didn't have an exhaust manifold nor a
distributor so these had to be moved from the old engine. Turns out the
old engine had a cracked exhaust manifold so we had to buy another one
($275 w tax ouch!). This one has the catalytic converter built into it.

Following engine installation, check engine codes indicating there was
a bad connection to the crank case speed fluctuation sensor that was
found and corrected. The mechanic indicated that the new motor was
surging and swapped the throttle body from the old motor over to the
new one. Then there was a check engine code for the secondary O2 sensor
heater. $104 + tax. Then another code after the new part was
installed:. Primary O2 sensor heater bad. $80! I'm dieing here! After
replacing the 2nd O2 sensor, we received another code pointing at the
secondary O2 sensor we had already replaced. This problem was traced to
a bad connection on the ECM. Many months ago my son had not quickly
addressed AC condensation collecting in the floor board on the
passenger side. This water had obviously caused corrosion in the "D"
ECM wiring harness connection. Oh, yeah this is the harness off the
original engine and that was the issue with the crank case sensor
mentioned above. Many hours latter, the connector had been cleaned up
of it's green corrosion. Not an easy chore. I understand that today the
check engine light came back on, however. We are pretty sure the O2
sensors were probably not bad after all.

I drove the Civic home but didn't notice the shake. I did notice a
little vibration when I first started it up but didn't think much of
it. It seemed plenty peppy and drove well. As soon as my son got behind
the wheel he detected the vibration. He was also distracted by the new
clutch. He said it was like driving a different car. He really first
noticed the shake while driving and downshifting.

We took the car back to the shop Tuesday and showed them the shake.
They suspected the engine mounts (came with new motor). They want it
back next Tuesday and will put it up on the lift so they can check it
out better. They also aren't ruling out the clutch or the resurfacing
of the flywheel. The shop owner asked that he avoid putting the car
into the situations where it shakes.

The problem with vibration occurs when driving and you downshift from
3rd to 2nd you feel the car shudder. A similar shake is easily
reproduced by having the car stationary and in first gear. Slowly
engaging the clutch causes the engine to shake fairly violently. It is
as if it doesn't have enough power to pull itself. The old engine
didn't do this as it was fairly easy to take off at idle using this
method. The car is also not capable of taking off in reverse at idle.


I saw another post where there was discussion of a timing belt being a
tooth off. That situation seemed to cause a rough engine at all times.
This problem seems to be only at idle while the engine has a load on
it.

Would bad motor mounts exhibit this symptom? Any other ideas would be
greatly appreciated.

 

Sounds like the mounts are bad... If a tooth was off on the belt,
you'd have more than shaking going on