Spark Plug Help *video*
 

Hello, I'm wondering what you guys would say about these plugs I have here. I've got a trailing plug (T1) that I don't think is firing properly. Plugs are BR10EIX gapped at 0.022.

Check out the video and tell me whatcha think. Right click and Save As....

http://www.zeroglabs.com/rx7/images/sparkplugs.avi

8 megs, divx

Thanks!

Brian

I think perhaps the T1 plug isn't firing at all and getting doused with gas . . . hard to tell for sure but it looks wet and clean (in a bad way) . . .

yeah I mean it does look like it's not firing... but I run with a wideband hooked up all the time and all the AFRs are very normal. The car runs well and makes good power on the dyno too so I don't -think- it could be an injector doing something bad. I've replaced the wire, tried another coil, 3 sets of plugs, checked the factory wiring (not ALL of it, but some) and everything looks right.

Brian

OK I swapped the two trailing plugs and went out for a 20 minute drive with two WOT blasts, and some 3-5000 RPM highway cruising.

Even after such a short time, you can clearly see that the plugs are "reversing roles". The first plug in my video with the black electrode is now turning medium brown and the other plug is turning from medium brown to a black electrode.

hmm. have you pulled that plug and cranked over the engine to actually watch it spark? I'd watch all 4 plugs spark, each seperately and compare to the one that is misbehaving. Perhaps it's not getting a good ground in the block with all that oil/fuel on the threads or something . . . . not really sure, just tyring to think of what it might be.

Right now I think that either my ignitor unit or the wiring is bad somewhere... My guess is that it's not even trying to spark but we'll see...

UPDATE:

Checked the wiring from the junction of the Engine and Ignition harnesses through the coils... ALL GOOD

Checked the wiring from the junction of the Engine and Ignition harnesses through to the ignitor ALL GOOD

Hooked up an oscilloscope to the wires going between the coils and the ignitor unit. Leading gets a nice signal, rear trailing sees a signal... front trailing is dead. Flat. Kaput.

So I'm down to 4 possibilities that I can think of.

1 - Ignitor module is bad
2 - Wiring between the ignitor and the PowerFC is bad
3 - PowerFC is bad
4 - Front Trail coil is screwed. (Unlikely since I already replaced it with a junkyard coil and it didn't help)

I'm hoping it's just a loose or damaged wire between the PFC and the ignitor.....

do you have an idea how long it's been doing this? and if so did it happen after any underhood or ecu work? i know these are obvious questions but every time you overlook the obvious.........

It has been doing this for at least a year, maybe longer (I'm not sure).

Interesting new updates for all those hanging on the edge of their seats on this one.

1 - Tested all wiring between the Ignitor and the ECU as well as re-checking all other wiring. ALL GOOD.
2 - Opened PowerFC and checked through as much of the Front Trailing circuitry as I could without my eyes going buggy. Everything looks/tests OK but I admit I'm not a circuitry expert.
3 - Tested my Ignitor with a digital voltmeter using some instructions for testing transistors on the web. Not sure if this is 100% valid for an RX-7 ignitor, but it seemed to check out fine.
4 - Replaced my Ignitor with a friend's Ignitor and tested.... His ignitor gave good readings on the ocscilloscope at idle! I thought I had found my problem, so I put my Ignitor back in and re-tested to confirm. Well guess what, now I AM seeing a good signal where I am SURE I wasn't the other day.

My current theory is that either all my extensive manipulation of the harnesses and connectors fixed a bad connection problem or a loose wire problem....

OR...

Something (the coil or the Ignitor) is getting HOT and then doesn't work right but it will work OK for a very short "start up and idle" test. I couldn't test it warmed up last night because the neighbors would get mad.

My next action is to test it cold (freshly started) with the 'scope.... Then go out and drive for 15-20 minutes and pull back in and test again. If it is heat-related failure I should be able to see that.