broken93

Dunno man, the current harness (the brand new one) still has the black box and a harness for it. So I assume that the black box was made permenant to avoid having to re-code the ECU (I assume it was easier to change the wiring harness production line and build black boxes than it was to scrap thousands of ECUs and change the ECU production line).

Engine is stock. Good compression.

I live in Huntsville. Feel like taking a day trip? Beer's on me.

I agree with you. I am going to check the CAS stuff one more time, just to be sure. Just to confirm, which sensor (white or gray) goes on the outside/inside?

I do agree that what I am seeing is consistent with a major timing problem, like the timing being 90 degrees out of phase, for example.

The TPS is reading fine, I carefully calibrated it to the specs given here:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/fixed-my-idle-problems-backfiring-bucking-more-170731/

One thing I have been wanting to do is swap ignitors/coils. I unfortunately don't have access to any, and I'm not about to spend another random $100 on something that I can't verify even might be the problem... if I had a buck for every time I took apart the UIM and swapped injectors in the last month, I'd have, well, about 25 bucks. lol.

Thanks guys for your help.

broken93

One more question... what does your fuel thermosensor read cold with the ignition on (not running)? I am seeing 4.1V or so; this seems a little high when the air temp and water temp are reading 2.7V or so.

I think perhaps the ignitor has failed?

J.S.J

I would think you could get a good idea of how the ignition timing was working by using ether a timing light or observing the ignition spark action. Since its clear the engine doesn't start you could mark TDC on the eccentric shaft/pulley and crank the engine using a timing light or just rotate the engine via the eccentric shaft and view the ignition spark. This should help you determine a run or no run situation. This does not speak to the fuel injector pulse or fuel volume. I view the fuel temp sensor is a "trim" input sensor to the ECU and could not cause the type of over-fueling you are experiencing.

scotty305

iTrader: (2)

To run the engine needs air, fuel and spark. You have chased down a lot of fuel problems, but how about air? Is it possible that you're not getting enough air? I'm guessing this because the car ran with the intake manifold removed, providing more air than you needed. You might try opening the idle adjustment screw completely, or removing the intake pipes after the throttle body (and maybe even the entire intake manifold if needed).

If none of those attempts work, then it sounds like you're back to chasing spark or fuel problems.

Good luck,
-s-

broken93

Throttle body is open to atmosphere. AICV is opening fully during cranking, reading 0 vacuum. There's plenty of air.

I think I am going to look into the timing light approach. Thanks again, guys.

broken93

Eureka. I hope.

I got a timing light. I put a timing light on the leading coil, and cranked the car. The timing light did not light. This is strange, since I have often pulled the plug wires off and checked for spark and always had spark.

I pulled the leading plug wire off the front leading plug and left it close to the block where it could jump to ground. Cranked the car. Got a nice blue spark, and the timing light lit. Put the wire back on the plug. Cranked the car. No timing light activity. Interesting. Moved the timing light to the rear trailing coil. Same result.

Pulled out a plug and measured the resistance from ground to the wire post. 20k +- 10k Ohms. Pulled another plug and checked that too, that plug was within about the same range.

I hypothesize: the resistance is there between the terminal and ground to limit the gap voltage prior to breakdown to some manageable level, since the voltage drop across the insulator during spark set-up (coil voltage rise on the pulse leading edge) would be finite and fairly large. This is probably in place to either save the coil or the plug from premature failure (for example, erosion of the metal from ionization). From what I have read in the last few minutes, most plugs will achieve breakdown at about 7kV, so there's probably little point in going much higher, except to account for the higher ionization energies of the fuel/air mixture versus just air.

Of course, this is unrelated to the resistance of about 1-4k Ohms/ft present in plug wires, which is in place to increase spark duration (by limiting current flow while dissipating a finite amount of energy from the coil).

In this case, it is likely that the ignition system can't provide enough power to initiate a spark when there is a current path to sink to ground through the insulator, but there is enough power for a spark when the resistance is infinite and the wire is not connected to the plug. On both my leading and trailing coils, front and rear, it appears that I have no problem getting a spark with just a plug wire jumping to ground (the block or UIM) but I have no spark when they are connected to a plug. This is further evidenced by the fact that the plugs are wet but not carbon fouled (they look new), like they have been soaked in unburned gasoline (hence, my consistent flooding problem).

Since I feel that it is unlikely that

a) Multiple (new) NGK BUR9EQ plugs from possibly different batches have the same defect - high resistance from the terminal to ground, and roughly the same (very low) resistance from the terminal to the tip.
b) Multiple ignition coils are failing in the exact same way. Possible, but unlikely.

What's the commonality? The ignitor. Looks like it's time to replace the ignitor, (and probably the plugs too for good measure) and I bet the problem goes away. Anyone have an ignitor for cheap?

Sorry about the extensive engineering analysis, but I am caffinated and excited. Comments welcome.

J.S.J

Try something first,
Remove one of the leading plug wires from the coil and just let it sit on the coil tower with the wire just inside the rim of the tower. Make the system throw a hot spark to the plugs. Try this with the plug dried off, (not flooded) In my view the igniter is just a set of points or a basic electronic ignition. An on/off switch. Typically it just stops working at all, I don't see effecting coil output other than not working at all. The amount of ignition spark or KV is a product of the circuit attached. As you said it in the post, both having said that the sum of the output by design should be enough to fire the plugs/mixture. I have worked with thousands of engines most with DIS ignition and have see some odd things happen with the waist spark system. Just give this a try it might make the engine do something different for a change.

broken93

Just in case anyone was wondering, I got it running correctly for the first time this weekend.

- I had a leaking rear secondary injector. I temporarily bypassed the secondary fuel rail completely, and that problem went away.
- Due to inadequate crankcase vacuum, I was getting some oil leakage from my rear turbine oil seal. Fixed that.
- The main problem: Bad plug wires. I replaced the leading wires with a new set of stock wires from Malloy and it suddenly sprang to life the right way, stopped stalling, decent vacuum, noticable power, etc, etc.

Quite the revelation to realize that all the time and money I spent replacing other parts was a $9 o-ring and a $34 set of wires.

Anyone need a spare ignitor, secondary injectors, um...

J.S.J

The truth is Sh*t happens. Some years ago I replaced a timing chain set along with a battery and starter on a V-6 which just needed a battery cable. The journey along the way has hurt your bank account but improved your knowledge. Great news. John St John