stickyRice

Hi all, I am presently absolutely baffled here.

As the title states, I'm not getting a spark on rotor #2. I have switched out the coils, plugs, and wires several times. I got a neat little tool that I can put between the wire and the plug, that lights up when it gets a jolt. This works fine on rotor #1, leading and trailing plugs.

Basically, I feel like I've ruled out plugs, wires, and coils. So, what's the next thing to look at? I've searched and searched, and can't seem to find anyone else with this problem -- where any kind of resolution was posted.

I'm also getting a cel about a problem with the ess sensor, so I replaced it. I also replaced that toothed disk behind the main pulley that communicates to the ess. This changed nothing.

2004 MT, 192k miles

9krpmrx8

iTrader: (46)

So you tested all four coils, wires, plugs? Did this start happening all of the sudden? Did the car drive fine before?

paimon.soror

iTrader: (15)

After you replaced the ESS sensor, did you do the 20 brake stomp to reset the profile?

stickyRice

Yes, all coils, plugs, and wires tested.

Not a simple answer to such a simple question!

It all started on New Year's Day, driving like normal with the whole family in the car, and then all of a sudden I'm driving a smoking tractor that has virtually no power. Couldn't even limp it up a not-very-steep hill a mile from home, and had it towed home. Did the plugs, coils, wires with no change. The plugs out of rotor #2 were really covered in shrapnel, so I figured I finally had it happen... something in there blew up and it's motor time.

Bought a used "longblock" motor out of a 2005 MT, 82k miles. Finally got it all in, and this is what's happening.

I know there's a million things that can cause a rotor not to fire, but I want everyone to know that I'm pretty sure I ruled out plugs, wires, coils, the cat, ess sensor, and even compression.

Could the car's computer fail in such a way that everything else works, but rotor #2 doesn't get his fire?

stickyRice

I did. I've done this a few times now.

CRO8TIA

To further diagnose the issue, have you switched # 2 rotor coils into the #1 rotor position and vice versa. The toothed wheel is installed the correct way, not reversed.

stickyRice

I have!

I really wanted to try everything to rule out coils, because I was really, really hoping the problem was coils. Because this sounds so much like a problem with coils.

stickyRice

From what I could tell, it would only go on in one correct way. Sure, it's reversible, but the screw holes don't all line up perfectly, except for one way that I could tell.

9krpmrx8

iTrader: (46)

How did you rule out compression? You really need to troubleshoot things in a methodical manner as outlined in the FSM. Did you test the actual wiring to the coils? Did you do a rotor balance test?

http://foxed.ca/rx7manual/2003mazdar..._S01_0016.html

stickyRice

The reason I don't think compression is the issue here is that I'm not getting a spark. I have assumed that if the ignition system is sending fire to #1, then it should be sending fire to #2, even if compression is off or rotors out of balance. Am I wrong here?

Just now, I'm reading through the FSM and studying the wires/connectors between the coils and the PCM. I guess my next step is to at least make sure none of those circuits are open, i.e. wires are not broken?

I appreciate your thinking about this with me. I'm just a dude, not a mechanic. Like I said, I make assumptions. We all know about those....

9krpmrx8

iTrader: (46)

Now you are thinking

CRO8TIA

When you used your tool to check spark, you had results on #1 rotor, but not #2, correct ?A compression test won't resolve no spark

stickyRice

Correct. Spark at #1 (both leading and trailing), no spark at #2 (leading, not 100% sure about trailing, but probably not).

I guess I'm hoping for a unicorn. Someone reads this and says something like 'oh yeah, it is definitely the pcm.' Or 'oh yeah, make sure [magical thing] is connected to [other thing], because if that's not right then #1 will work and #2 will not.'

9krpmrx8

iTrader: (46)

You have to check everything, otherwise you end up guessing, assuming, and wasting money. Especially when you have just had an engine replaced.

stickyRice

I did continuity testing on the wiring harness, between coils 3 and 4 and the PCM, and they passed. Also did another exhaustive set of tests on coils, wires, plugs, and definitely rule them all out as culprits. Also did another round of testing to confirm no juice flows to plugs 3 and 4.

As I understand it, if I need a new PCM, it's not as simple as buying one off eBay and swapping it in. Does the Mazda dealer really need to do this because they have to code it to my car?

9krpmrx8

iTrader: (46)

I dunno man, ECU failures are rare. And yes sometimes they require a trip to the dealer for a flash. Tough to diagnose over the internet though.

stickyRice

Replaced the "condenser" (a capacitor in the ignition) and it started right up. All plugs sparking!

And I had read somewhere that modern ignition systems don't even have these...

9krpmrx8

iTrader: (46)

I have never heard of that going bad.

https://www.rx8club.com/series-i-tec...5/#post3806990

Harlan

iTrader: (3)

Damn that is a new one... I never knew those were capacitors, but it make sense. Probably put there to lessen the current surges/emi from the coils charging. If it pops and shorts to ground it could prevent enough charge from getting to the coils. I need take a look at a wiring harness now....

Legot

iTrader: (1)

I just had trouble with that thing being in the way and I was wondering what it was! Weird, glad you fixed it.

TeamRX8

iTrader: (25)

If it was bad it should affect all coils. Seems more like a poor connection or ground contact IMO

stickyRice

My thoughts exactly. Before I switched out the condenser, I had tested for continuity all of the coils' harness wires. Then I used a multimeter to test resistance on A, B, and C (between the coil and PCM), and for 12v on C (with key turned). I had also cleaned and re-affixed my grounds to the engine and chassis. Everything checked out.

I even created a little device that I could hook up to where the coils plug into the harness, so that I could see an LED light up each time the pulse came over A while cranking the engine. From this I learned that the leading #2 was actually getting a pulse (I was expecting to see nothing)! I checked for spark again, and nothing. At that point I was ready to ask the universe what I had done to offend it...

I was curious about the condenser so I started researching it, and discovered somewhere, on some forum, someone was discussing it and questioning it, etc. Someone replied with a single sentence, something like 'if it's not there, you'll get bad misfires.' So, on a lark, I replaced it with my old one. The one I replaced was actually cleaner (the contact) than my old one, so I don't really think it was a grounding thing there.

9krpmrx8

iTrader: (46)

Glad to hear you got is sorted. Persistence and troubleshooting pays off

TapaRx8

Had a severe power loss and the engine just stalled and died, tried putting in new plugs, wires cleaned injectors but I'm not getting spark on rotor number two i even changed the capacitor or is it condensor but still leading and traling both don't fire, idling rough on one rotor.... Initially there was no gas going to the plugs hence i cleaned my injectors now im getting gas but no spark rotor number 2

Help

stickyRice