I recently purchased a 1996 Infiniti I30 5 speed w/200k miles. It ran great until 2 days ago. NOTE - No CEL throughout this process.

I heard a metallic metal scraping sound - here is YouTube link -
As I was trying to diagnose the problem, engine acted like it was running on 2-3 cylinders.

When I removed the inspection plate at the bottom of the bellhausing, I could feel the loose metal plate on the engine side of the flywheel and some metal shavings. Scraping issue identified.

Because of the performance issue, I was concerned the timing chain may have jumped a tooth.

I decided to pull the engine and transmission to figure out next steps.

There should be nine bolts holding the plate to the flywheel - there were ZERO. How it stayed on the flywheel for as long as it did is a mystery. It does not look like any significant damage to the plate or engine, just some rubbing when it was being bounced around while the flywheel was turning.

My thesis is the rattle started but the plate stayed on the alignment pins. When it fell off the alignment pins, started having engine performance issues, because the "flywheel" was not turning (per the Crankshaft Sensor) but the crank obviously was. Again, no CEL.

Here are my questions:

Have you seen performance issues of this type simply from a bad reading on the Crankshaft Sensor? After seeing the setup, it looks unlikely that the restriction from the plate would cause the timing to jump.

Now that I have the engine out, I am planning to change water pump, clutch/pressure plate/throwout bearing. What else would you do that is a PIA to do while in-frame?

The bolts for the crankshaft plate appear to be the same size as the pressure plate bolts. Any suggestions on where to source these bolts?

Thanks! Lance

 

Just thinking out loud.....

if the flex plate is flopping around like that, the sensor will report a signal based on where the flex plate magnet is. If it was bolted securely, the magnet would corrospond to where the crank or cam is at the time.

So a loose flexplate would essentially tell lies to the ecu. The ecu would believe the lies, so the engine would run badly, while no cel would be set.

Fixing the flywheel should/might fix how the engine runs as well.

This is particularly true if the two issues were noticeble at the same time.

Few members have reported a slipped timing chain.

Since the engine is out, consider dping the water pump and tensioner. Leave the timing chain alone.

this would be a good time to change the front and rear main seals. Inspect the harmonic balancer or front main pully whole you are at it.

The egr system on this engine will need cleaning out sooner or later. Also the valve covers eventually leak. The fuel injectors often fail. The knock sensor is buried under the uim. Since the uim needs to be removed to service any one of these, you might as well do it all at the same time. The injectors can be rebuilt so they function as new. At least service the back ones.

 

The mounted and bolted down clutch should look like this picture.

 

Sounds like the op has a flex plate, attached to an automatic transmission

 

It's a 5 Speed. The plate that was rattling is on the engine side of the flywheel and provides the signal for the Throttle Position Sensor.

Judging by the orange silicon on the oil pan, seller recently did some rear main seal work. How someone can forget to attach the 9 bolts to the flywheel is beyond me? Why they removed the bolts in the first place is also a head scratcher.