Alrighty boys - an update:

Seems as the timing in the engine is off minimum one tooth (almost looks like 1-1/2 tooth?)

Regardless - I'm going to reset base timing tonight and re-check compression.

Will update soon. Thanks for everyone's input.

https://cimg1.ibsrv.net/gimg/www.mia...52cbecfbd8.jpg
https://cimg7.ibsrv.net/gimg/www.mia...f6daf32b90.jpg


Attachment 227996

Attachment 227997

Exhaust cam looks ok, intake looks off by a tooth.

VVT will alter cam-to-pulley orientation but not pulley-to-belt or pulley-to-pulley.

Agreed.

Dissagree. In the 1st and 3rd pictures the intake cam looks spot on and the exhaust cam looks off

Well, regardless of what exactly was off - I dug into the engine and reset the static timing (crank, cams, tension, etc) - I put everything back together, warmed up the engine and re-checked compression.

First check gave me 50psi - this was because I had forgotten to wire the intake WOT.

After fixing that, I tried again - I got +/-100psi, straight across the board. :mad:

This was pretty frustrating, and I was doubting my timing reset - so I removed valve cover / timing belt cover and re-verified static timing. Everything looks spot-on.

Camshafts/Lifters/Springs had good movement, no damage / defects, everything looked good (hand turning the engine).

So, at this point it looks like a full removal and tear-down is in order.

https://cimg0.ibsrv.net/gimg/www.mia...bad3f80738.jpg


https://cimg2.ibsrv.net/gimg/www.mia...0ab1ab57af.jpg


https://cimg8.ibsrv.net/gimg/www.mia...9346dabae5.jpg

You said a leak down test was planned. Where are the results?


I've used 3 different compression testers on the same engine and gotten readings that varied by 50psi.

This company makes the compression tester, and other gauge sets for snap on. If you can afford it this set is worth it. Their leak down tester is $85 on amazon, worth the premium over harbor freight for peace of mind.
SKU : TU-30A - Compression Tester Set - Lang Tools

Nothing yet on leak-down info - borrowing a tester today from NAPA, will use tomorrow. I'm hoping I ran into a bum tester. If I don't get good results with the NAPA unit tomorrow I'll just pull the whole things and start a tear-down - just to get my eyes on things, then go from there.


Thank you for the tip - looks legit!

Decided to check ignition with a timing light - my light I reading spark from cylinder 2/3 but not 1/4.

The car does start and run, which pretty much rules out ECU issues.

I double checked grounds, as well as 12+ to the 1/4 coil pack - I do have switched power.

Then I ran the car again, noticed that the coil pack for 1/4 was getting EXTREMELY hot - after running 20/30 seconds?

So I swapped coils - same problem - then I swapped in a back up set of coils - same issue - whatever coil is plugged into the 1/4 harness is getting SUPER hot, and I'm still not getting spark at cylinders 1/4.

Thoughts? (Found out no local autoparts store loans compression or leak down testers - so that's delayed - spark is my foremost concern right now)

I would replace plugs and wires, just to rule out.

Plugs / Wires are new, less than 300 miles on them.



Alrighty. Didn't make much more progress over the weekend from my previous update.

Some Info:
The ONLY wiring on the car that isn't 'stock' is the old Flyin Miata Link ECU.

The Link ECU interrupts the signal from the stock ecu to the spark plugs - (2) stock wires and the 12+.

Seen in this install image:

https://cimg6.ibsrv.net/gimg/www.mia...bce97d7279.jpg

Attachment 227995


SO, I've verified that the 12+ wire is installed correctly, supplying voltage only with the key in the 'run' position. I then double-checked the connections between the Link wires and the stock ECU wires (Brown/Yellow, Black/Yellow) - everything looked good.

I don't believe it's a wiring issue - I think it make be an ECU / trigger issue, possibly turning the injector on ALL the time, therefore over-driving it and overheating the coil. Need to check those supply wires.

Sounds like your Link is fried. I say ditch it asap, there is a reason they are so reviled around here.

100%

Actively looking for an MS3 - suppose the smart route would be Squirt the car, get it running and happy, then look at engine internals.

I've posted on other forums, consensus seems to be the Link - need to verify that the coil trigger wire is seeing constant voltage - that would suggest bad signals from the Link.

Hate to say but with those compression numbers (repeatedly)-- its probably not gonna be "happy" until it gets some new rings and a hone.

Welp, some more progress:

Decided to disconnect the Link ECU entirely. Did so, checked spark with my timing light - still no spark in 1/4 cylinders.

So, I'm poking around now trying to determine if anything out of place - hoping it's not the stock Miata ECU.

After getting the Link uninstalled I took some measurements at the coil pigtail connectors. I did the measurements with the ECU connected / disconnected, and with key on / key off, here's what I got:

ECU connected, Key On
Inj 1
BR/W, 1.86 - B, 4.1 - B/W, 12.24
Inj 2
B/Y, 32.8 - B, 4.0 - B/W, 12.16

ECU connected, Key Off
Inj 1
BR/W, 2.2 - B, 0.0 - B/W, 0.0
Inj 2
B/Y, 2.2 - B, 0.0 - B/W, 0.0


ECU disconnected, Key On
Inj 1
BR/W, 0.0 - B, 0.0 - B/W, 12.3
Inj 2
B/Y, 0.0 - B, 0.0 - B/W, 12.3

ECU dissconnected, Key Off
Inj 1
BR/W, 0.0 - B, 0.0 - B/W, 0.0
Inj 2
B/Y, 0.0 - B, 0.0 - B/W, 0.0


One observation:
When checking Inj 1 (runs coils 2/3) when taking a reading on the BR/W wire with ECU Connected, KEY ON, I got the 1.86 reading (was 32.8 on B/Y wire on Inj 2), AND I got the red "X" lit up on the Battery Load Test function of my multimeter (not illuminated for B/Y wire on Inj 2 which runs 1/4, the "problem" coil)

To add, the Green "check mark" lit up on the Battery Load Test function of my multimeter when checking the B/W wires for BOTH injectors, ECU connected AND dissconnected, KEY ON

Thoughts?

Well, an update:

Double checked - Coil 1 (cylinders 1/4) still gets hot to the touch after 10-20 seconds of operation.

Also double-checked the voltage at each coil pig tail - these are the readings I got (ECU connected, Key turned to "run"):

Coil 1 (Cylinders 1/4)(No spark)
Br/W - 1.6v, B - 0.0v, B/W - 12.0v

Coil 2 (Cylinders 2/3) (Has spark)
B/Y - 25mv, B - 0.0v,. B/W - 12.0v

The only difference seems to be the Brown/White wire and the Black/Yellow wire. I believe this difference is what's causing no spark and overheating in Coil 1 - thoughts?

Didn't read word for word: let me summarize my thoughts.

1) Timing lights aren't how you check for spark. Use a test light connected to ground, or an inline spark tester.

2) Confirm good 12volt input at each coil, it should be constant with key on, engine off. Use a test light, or load the circuit in someway. Open voltage with a meter tells you little; although this is doesn't sound like your issue, since they have a shared power feed. Unless you have an issue between the splice and coil connectors.

3) Swap coils between 1/4 and 2/3. If your spark moves, you have a coil failure. Why? Well either random failure, or environmental. I've had defective plugs out of the box; wires too. No output for 10k volts and higher means dead coil. I would be performing all spark/no-spark testing with the COP unit bolted down, testing from the output of the coil body where the wire connects. Of course, you could have a single dead pole on one coil. Again, doubtful. Swapping the coils eliminates this possibility.

4) ECU switches the ground to control primary side of the coil. If your readings are different at the control wires, you have 2 options.




A) You have an open or voltage drop between the connectors at the PCM/Link/Coils. 12 volt input supply can be load tested at the connectors for the coils. However the other two wires need checked between the coil, and the ultimate source of control. Disconnect all players, Input 12 volts through each relevant wire, ground a test light at the output. This confirms ability to move sufficient current to operate the coil. ALL inputs from PCM to coil connector, Coil connector to link, and link back to PCM need checked. If you want to be lazy, remove the Link piggyback (eliminating it), and check from PCM connector to coil connector

B) You have a failed coil driver (my suspect), which is not fully pulling the coil to ground. I assume pins 3I and 3F are the ECU coil driver grounds on your diagram? If this is the case, I would be replacing that ignition coil before replacing the ECU.

Well, some good progress:

Grabbed a complete ECU/Immobilizer Box/Ignition Ring/Keys from a friends ride, swapped them in, started right up. Verified spark at all (4) plugs, everything looked / sounded good! Took her out the next day for some pulls - ran just like she used to, tons of power, great sound.

After about an hour or two (or three?) of gunning it through canyons, the car just stalled and stopped, temp spiked. She wouldn't turn over quickly enough to fire the engine, requiring a tow. After getting her home, I started going through the whole 'air, fuel, spark' tests.

Pulled spark plug #1, smelled faintly of gas and spark checked out.
Pulled spark plug #2, didn't smell much gas. Went to verify spark and got a mini 'Old-Faithful' out of cylinder #2. (Same for cylinder #3 btw).

Attachment 227993

Attachment 227994

The liquid was watery slippery. Smelled slightly of fuel, but not much. Had a green tint to it, obviously coolant.

SO

Pretty sure the head gasket blew. Maybe I should have seen it coming with compression numbers being so low? IDK. I don't think it's a cracked block/head (fingers crossed), and this kind of failure wouldn't be from any of the other coolant / seals. OEM Miata gasket kit is in the mail, I'll update when I get into things farther.

Change the coil that was an intermittent no-spark. If I'm correct on my hunch the ECU driver was at fault, that coil may have been the cause. Coils are relatively cheap, and if there is a coil issue which killed the previous ECU driver, the new ECU (and its driver) will also fail.


My preferred head-gasket test is using a leak down tester, if you have access to compressed air. If there was significant coolant in the combustion chamber, I would be concerned of a bent connecting rod from hydrolock. IF the pistons can be cleaned enough to be totally carbon free on the crown, a machinist straight edge and a feeler gauge should reveal any significant rod length changes.