97 Civic w/ DI6Y7 engine shakes badly at loaded idle

Just a few days ago, following a loose harmonic balance spinning on the crank and grinding off the spline gear teeth of both parts, a salvaged motor from a 94 Civic was installed by a local garage in my old enough to know better, son's car.

The business 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 that installed it for us said the engine looked very clean inside and out. Recommended parts were replaced. These included: Timing belt, rear main seal, valve gasket, water pump, clutch (flywheel surfaced), pressure plate, bearing, thermostat, etc. The salvaged engine didn't have an exhaust manifold nor a distributor so these had to be moved from the old engine. But then we find out that 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. The mechanic told us that the new motor was surging so he swapped the throttle body from the old motor over to the new one. After that the engine sounded nice and smooth but it had a check engine code.

Following engine installation, check engine codes indicating there was a bad connection to the crank case speed fluctuation sensor that was found and corrected. Then there was a check engine code for the secondary O2 sensor heater. $104 + tax. Then another code after the new O2 sensor was installed:. Now, the primary O2 sensor heater shows 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. After some effort, "we" traced the problem to a bad connection on the ECM. Oh, yeah this is the harness off the original engine. Many months ago my son had not quickly addressed the AC condensation collecting in the floor board on the passenger side. This water had obviously caused corrosion in the "D" ECM wiring harness connection. Many hours latter, the connector had been cleaned up of it's green corrosion. Not an easy chore. 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. He said it seemed to have about the same horse power as before.

We took the car back to the shop Tuesday and let them check out the shake. They suspected the engine mounts may be the cause. Those came with new (salvaged) motor. They want it back this coming Tuesday (our date) 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 we avoid putting the car into the situations where it shakes until then.

The problem with vibration occurs when driving and you downshift from 3rd to 2nd you feel the car shudder. This seems really odd as this is sort of a "reverse load" situation. The shaking is easily produced by having the car stationary and in first gear. Slowly engaging the clutch causes the engine to shake the whole car causing all sorts of rattles. It is as if it doesn't have enough power to pull itself but we never actually let it die so I'm not sure that lack of horse power is a factor. Of course, the old engine didn't do this as it was fairly easy to take off at idle using this method. The car also will do the shake if your try this in reverse. If you give it more RPMs, no problem.

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 verses the problem we see which 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.

 

The clutch might be bad, warped, or off axis. You're lucky it runs at
all. You can't build Frankenstein's engine and expect things to go
smoothly. It's clear from your post that the engine parts don't match.

 

Correction: The donor car was a 98 Civic with 94K miles.

Just a few days ago, following a loose harmonic balance spinning on the crank and grinding off the spline gear teeth of both parts, a salvaged motor from a 94 Civic was installed by a local garage in my old enough to know better, son's car.

The business 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 that installed it for us said the engine looked very clean inside and out. Recommended parts were replaced. These included: Timing belt, rear main seal, valve gasket, water pump, clutch (flywheel surfaced), pressure plate, bearing, thermostat, etc. The salvaged engine didn't have an exhaust manifold nor a distributor so these had to be moved from the old engine. But then we find out that 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. The mechanic told us that the new motor was surging so he swapped the throttle body from the old motor over to the new one. After that the engine sounded nice and smooth but it had a check engine code.

Following engine installation, check engine codes indicating there was a bad connection to the crank case speed fluctuation sensor that was found and corrected. Then there was a check engine code for the secondary O2 sensor heater. $104 + tax. Then another code after the new O2 sensor was installed:. Now, the primary O2 sensor heater shows 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. After some effort, "we" traced the problem to a bad connection on the ECM. Oh, yeah this is the harness off the original engine. Many months ago my son had not quickly addressed the AC condensation collecting in the floor board on the passenger side. This water had obviously caused corrosion in the "D" ECM wiring harness connection. Many hours latter, the connector had been cleaned up of it's green corrosion. Not an easy chore. 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. He said it seemed to have about the same horse power as before.

We took the car back to the shop Tuesday and let them check out the shake. They suspected the engine mounts may be the cause. Those came with new (salvaged) motor. They want it back this coming Tuesday (our date) 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 we avoid putting the car into the situations where it shakes until then.

The problem with vibration occurs when driving and you downshift from 3rd to 2nd you feel the car shudder. This seems really odd as this is sort of a "reverse load" situation. The shaking is easily produced by having the car stationary and in first gear. Slowly engaging the clutch causes the engine to shake the whole car causing all sorts of rattles. It is as if it doesn't have enough power to pull itself but we never actually let it die so I'm not sure that lack of horse power is a factor. Of course, the old engine didn't do this as it was fairly easy to take off at idle using this method. The car also will do the shake if your try this in reverse. If you give it more RPMs, no problem.

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 verses the problem we see which 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.