...or tell me who can.

Symptoms: 1988 Rx-7 nonturbo appears to get breakup up top from 5000-7500. AFR's on the dyno were kinda bouncing up and down. On the street the wideband fluctuates as I get up into that RPM range. It feels like it gets more noticeable right around 7000. I've replaced the plugs. That helps a bit. The wires are carquest 7mm stock replacements with like 5000 miles on them. zxappeal put a timing light on it recently and made sure it's on the mark.

The ignition system on these cars consist of a crank angle sensor and for our purposes a coil pack with a coil unit and an ignitor unit. How do I tell which one's bad? I could get a coil w/ ignitor used for like $40 or something, but how do I know that that's in spec? The factory service manual has a spec for resistance, but I've been told that the resistance doesn't tell you all that much (part could be in spec but still be bad). A friend said I could find someone with an ignition oscilloscope who could help diagnose it. Anyone know anything about those?

A brand new OEM coil is $236 and an ignitor is $287. I'd get them used, but once again how can I be sure that the part is ok? Btw, this is running on the stock ECU. I've got the Megasquirt, but I'm only running on it occasionally b/c the basemap sucks on it and tuning is proving difficult. I don't think the car is leaning out either. AFR's drop to the 11's around redline.

7/13/2006 8:27:24 PM

Quote :

"A friend said I could find someone with an ignition oscilloscope who could help diagnose it."

Ray...that's really the only way yer gonna know for sure. Gotta make sure you got de waveform.

Now, on another note, it's possible to use an inductive pickup on a plug wire and jack it to a recorder of sorts through the mic jack. Upload it as an audio file and then scrutinize it with some kind of spectrum visualization/analysis software.

7/13/2006 8:30:27 PM

um so who do I go to that won't charge me $200. At that point I might as well just buy a whole coil pack (someday) for $480ish

I just want to know what's wrong and your suggestion about using a mic jack reveals your proverbial African ancestry

7/13/2006 8:35:47 PM

Sure...I mean, where do you think I got my curly hair?

7/13/2006 8:38:25 PM

ordered an MSD box for $160 shipped. that seemed to be the best option to hopefully fix this thing. All the shops I called wanted $75 for diagnosis, and I'm not gonna mess with used parts unless absolutely necessary.

7/14/2006 4:16:44 PM

DONT SHIFT THAT HIGH

[Edited on July 14, 2006 at 4:57 PM. Reason : .]

7/14/2006 4:57:15 PM

yeah, i got a solution, don't drive like a jackass

7/14/2006 5:03:28 PM

Wankel, man. You should be able to tach to 10k.

And how do you know that it's ignition breakup?

Oh, and BTW, there are resistance values published for coils in repair manuals. I believe I have the details in my big book at home. I should have thought of this earlier. That's the FIRST thing to check.

Ray, I gotta say that 160 dolla for an MSD box (I'm presuming 6AL) is quite a bit more than for an hour of diagnostic time. I was thinking that my pal Rex over at Happy Jap's might actually have some insight into the matter (without needing to charge you an hour for labor right off the bat).

Here's another thing: you need two MSD boxes for those cars, if I'm thinking correctly. Hold on, that's for the 12A true distributor engines. Actually, how in the heck do you even wire an MSD box in? For all intents and purposes, your ignition is distributorless, and the coils receive individual impulses via individual leads from your ECM.

7/14/2006 8:43:07 PM

I've had ignition problems before on the dyno and I could never figure out what it was. I'm tired of messing with it. Honestly, I'm getting impatient. I've decided to take the car to Carolina Auto Masters for tuning. They will road tune and dyno tune for $400. They suggested I get all the bullshit out of the way before I try to take it in.

http://fc3spro.com/TECH/HOWTO/CDI/cdi.html

Actually, this car would technically need 3 boxes (I bought one regular 6A). The leading uses one and the trailing uses two... the leading ignitor fires both plugs at the same time so that's why it only needs one, and there's something about the trailing that makes it have two separate ignitors. But the trailing is practically useless for performance purposes. Hardly anyone runs 3 boxes unless they are retarded enough to try and use the rev limiting feature.

I've already checked the resistance on the coil per the factory manual, and it is in spec. It turns out that Mazda has a special tester for the ignitor which (hopefully) tests the waveform, but they want $75 for that test. At this point I feel that if I spent the time and money necessary to check the waveform I would only find out that I need a better ignitor, and a brand new one is $280.

If this doesn't fix it I may take you up on your offer to talk to Rex.

7/15/2006 2:02:45 AM

this car better be fast when it's tuned ! that's a lotta cash!

7/15/2006 10:48:00 PM

It won't be that fast. If I keep it at full weight like I am right now the best I could ever hope for is a car that could hang with a bone stock FD that's running right. This is pretty much the last naturally aspirated power mod I could do without tearing the motor down and doing a full bridgeport.

7/16/2006 3:31:12 PM