Originally Posted by 2ndGearRubber
(Post 1555309)
Change the coil that was an intermittent no-spark. If there is a coil issue which killed the previous ECU driver, the new ECU (and its driver) will also fail.
Originally Posted by 2ndGearRubber
(Post 1555309)
If there was significant coolant in the combustion chamber, I would be concerned of a bent connecting rod from hydrolock.
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Potential for computer damage, via coil failure, is really just a product of how an ignition coil functions. Long story short, a short or partial short in the primary winding is what kills the ECU drivers. Total current flow of a straight piece of wire with zero effective resistance vs. the windings of the coil primary side is significant. If there is a short within the primary, current levels can be higher than expected, damaging the driver. Manufacturers and their engineers have finally gotten wise to this, I went to a FCA training event a few weeks ago and basically every driver on their new ECUs have current limiters which will disable the drivers if excess current flow is detected. I seriously doubt the miata ECU has current limiting drivers, but you never know. IMO if there is a concern of a damaged driver in the ECU, the driven component must be thoroughly inspected. Unless you have a lap-scope, there really isn't a good way to do this. Really I would only worry about the coil which was not being switched properly. If the other one worked fine, I wouldn't say it's required to be changed. Of course, coils aren't crazy expensive either.
This is the enjoyable aspect of my day-job, so I enjoy nerding out about it. :party: Good luck with your exploratory surgery on the motor. |
2 Attachment(s)
Slight Update:
Pulled the engine/trans. Disassembled the engine down to the bare block (notice the nasty, brownish looking oil - MAJOR coolant dilution): Attachment 227991 Looked over the whole thing in detail - some minor scoring on the cylinders, pistons/crank/bearings looked fine. No rods bent (a concern was hydro-lock from the coolant in the combustion chambers.) No cracks (visible or felt with fingernails - very 'high tech' analysis.) No worn-in ridge/ring at the top of the cylinders either. In the process discovered this - beside the oil squirter for Cylinder #4: Attachment 227992 Some of you know what this is - caught me MAJORLY off guard - those ragged edges looked so bad - I spent the night convinced I had grenaded my block. Turns out NOT to be a hole / casting defect, rather the oil return/drain passage for the head. PHEW. Haven't gotten the any parts to a machinist for measurement - nothing within 3hrs of my location - will do this soon. The overall condition of the block/bore/crank/bearings seem promising - possibly just need a good cleaning, honing, rings/bearings/seal job? I did take a look at my valve lash (thanks Greg Peters) - nearly HALF of my lifters don't fully close due to poor adjustment. It's possible this is where my compression test issues (look back a half-dozen posts) seem to have originated. Still doesn't explain my primary engine issues. |
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