weird hiccup at 5000-6000rpm
 

I just ripped on the car and in 4th and 5th I'm getting a mystery hiccup where the tach drops 500-1000rpm in an instant and it feels like the car misses. 11.5:afr, very conservative spark table...so I'm not really sure what to do next. Its not showing in the logs either (and my notebook decided not to boot today). WTF is going on?

I suspect this is engine management related due to the tach behavior similar to "burning" when using MS.

Thoughts?

new plugs btw

Loss of CAS/CKP signal?

Mine did that last summer, I beefed up every ground I could find, but Joe had offered some other fixes if you search for the thread.

Let's see those logs!

The log shows nothing. I can't post the log because the computer won't boot.

https://www.miataturbo.net/megasquirt-18/losing-spark-tach-5000rpm-under-load-36299/

Joe mentioned this was one of the reasons he went to a trigger wheel.

I can't think of anything that wouldn't be in the logs... Before the plugs it ran fine? The A/FRs don't change during the hiccup?

Edit: The above post/thread sounds logical.

What year miata is this, and is it running a factory-style ignition system?

1991 with MSPNP9093 running savington's cops on the 1.6 cam angle sensor. It did this before randomly...maybe once or twice per month or once or twice per track event. . The plugs are fairly new.

AFR will jump from 11.5 to 12.0 or so during this hiccup.

I'd kill for a crank trigger/hall setup right now. I've wanted one for a long time but I can't do the math nor do I have the brain to design what I need. I can run a hall and trigger wheel on MSpnp, right?

Got a spare CAS? If not I can send one.

Mine went away with a reflash, but the CAS did randomly die a few months later.

I do not have a spare. I may take you up on that offer, but I'm going to bug someone to send me a hall wheel...thanks for the offer.

Yeah, this does sound very familiar.

Cap mod done?

Moar ground wires to head?


If you're serious, I'll PM you a name and a city, it's all I've got to go on right now. Send me your shipping address and I'll ship you my crank trigger setup. Do a good job on this, and some associates of mine may be interested in retaining your services.


You can use any sensor with an open-collector output. Most aftermarket trigger wheel pickups are VR, which would require a little re-wiring, but an NB crank sensor would put out the correct signal.

I have not modified the board because I've never soldered or played with a circuit board and I'd rather not start on a $700 computer that makes my car "work". I guess I could send it to DIY and get the TPS mod done too.

I can add a few more ground wires to the intake plenum and chassis.

Link to details on NB crank wheel? I want to fix this with the most simple method possible because I don't really know what I'm doing with electronics and configuration.

edit: I bought tuner studio.

I guess when I feel better I'll try to improve the grounding points with some cable and rings.

OK, you need to get a datalog of this happening. There very well may be a clue, even if it's subtle. The fact that your tach drops out is very telling, since your tach is driven directly off your coils.

Something like a loose main power or ground connection to your coils would do this.

Does manifold pressure have anything to do with it--can you pull to high rpm at 100kPa without a problem? The other very real possibility is a misfire due to not enough ignition energy. New plugs and/or smaller gap would solve that, or hotter coils.

I'll make another log tomorrow if its dry.

I'll check the connections tomorrow since this is fairly new in terms of frequency.

Yes, it won't misfire at low MAP. I have .045" plug gap and that's worked fine previously even at the track. The plugs are roughly 300-miles old.

+1 for spark blowout

Too much gap for the coils and MAP.

Reduce gap or get LSX/ MSD coils. Sounds like the cops are starting to slowly take a downward turn

OK, I added dielectric grease to the plugs gapped at .040", added 2 10awg GND wires from the intake plenum (MS GND) to the block and to the chassis. It hiccupping at high load where the log stops all together (the end of the log). I tried several times and it keeps killing the log at the hiccup.

thoughts?

I used the same MSQ on both logs. #1 (go to time 570) and there was no hiccup. Log #3 has the hiccup at the end.

I can't run a gap any larger than .35 without getting blow out.
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I've been running .5 and its been fine all along, even at 16psi. I guess I can take them down to .3 tomorrow and see what happens.

With COPS and MS I still never went over .041...

No wonder the DOW dropped 1000 points.

I vote for smaller gap too.

Too much gap. The misfire is killing the log. You'll need to run less gap or more coil.

In for your $268 worth of race coils...after all, size matters.

+ a few! Re-gap your plugs, if for any reason, just to find out what happens. It wont cost anything. I cannot run more than a .022 gap with COPs without blowout @ 18psi.

Screw that, I'll smash teh plugs back down today...I'm in the market for a Kayak ATM.

I'll put them at .3 then try .2 if I must. Those DIY coils are sexy-time but I don't care to spend any more money on the car, nor do I have the brain power for that.

You shouldn't have to go much below .035, but I know you are moving a lot more air than most of us.

What kind of kayak? Recently did a lot of research, ended up with a decent SOT, but highly recommend splurging on a Hobie after getting out on the water. Mine doesn't track well, and I ended up making my own custom dual bladed skeg to cover more ground with less corrections.

This is only 11psi at 250whp.

I'm looking for a POS on craigslist. I'm not dumping stupid money into a kayak.

So why would spark suddenly blow out when its been fine for over 1-year?

And why would a misfire kill the logs?

In that case the Pelicans are the best bang for the buck. I found a $400 one for $250 that had been used twice, and the guy threw in a decent paddle (worth paying for).

Good luck paddling, it's a lot of fun, and great exercise weakling.

I can't see the logs at work, but maybe take a look at your voltage. Charging system issues can cause this, and it may be an early symptom of a weak alternator.

I have extras if so, including one that was "rewound" and may put out a little more amperage. Yours for the usual favor...

I run the BKR7E gapped to .032 IIRC... whatever they come pre-gapped to, I just make sure they are all identical before installing. This is at 22-23 psi with a single MSD coil and a distributor, 8.2:1 compression. No blowout ftw. Upgrading to DSM turbo coils shortly, and hopefully opening up my gap a bit as a result.

Misfires of this nature will create all sorts of awful electrical noise, which can do weird things such as cause a datalog to terminate.

Ignition coils degrade over time. They are consumable like a belt or tires, and they'll wear faster the harder they're pushed. Big gaps through lots of boost is pretty hard on coils.

If it weren't for DIY and the braintrust here, I wouldn't have a car like this. I'm going to attempt to stay out of the bars tonight and close the gap.

Bring the plugs with and gap them at the bar. Problem solved!!!

Plugs are gapped at .022 and still hiccuping, here's the log:

This is at 123.953s? Can you post your msq?

Its the same .msq I ran before (trey 5-10-10). I can't see the log at work, but the hiccup is at the end of the log, where it dies.

Thanks for taking the time to deal with my problems and ignorance.

like i said before, i think your coils are taking shit. i bought my ls2 coils from this guy

http://cgi.ebay.com/ebaymotors/GM-LS...Q5fAccessories

If my coils are dying I'll just take the summer off, chill, then buy the DIY coils when someone makes a kit to wire them up with a mounting plate. I'm too dumb to figure out which resister goes where with all the other electronics that I don't understand and don't care to experiment with considering the cost of an engine or at the least $300 in coils when I screw it all up.

You could stand to run some more dwell. Try 3.0ms instead of 2.0ms of running dwell that you have now.

You could also try a DSM ignitor with your stock coil pack. Should be PNP and a pretty healthy upgrade over the Miata ignitor. The Miata 1.6 coils are ok; it's the stock ignitor that's weak-sauce.

Ummmmmm, so I'm a total idiot. It seems that the COP mounting plate was loose and vibrating in the front. I tried about 3-times to recreate the hiccup and can't seem to do it and I'll try more today.

I really feel like an idiot. Thanks for the help everyone.

Haha, glad you found out what it was.

I was experiencing blow out recently on the track. Turns out my OEM coil pack was loose. Those parts don't like vibration.

Ok, I went from head to toe through the wire harness and every wire looks "good enough." I went from the cops, to the igniter, to the fire-wall, to the computer. I drove the car today and its still blowing out and I've noticed the tach dropping out when shifting at redline almost every time. I will try the new to me CAS and 4-new to me Toyota coils. Any thoughts before I start my quest?

I'm really looking forward to DIY coming up with a how-to on wiring their coils.

Are you still on an MS1? The MS2 can significantly help debugging shit like that.

Mspnp 9093...so yes, MS1.

Ok, I have a new-to-me CAS, coils, and plugs and this thing is still dropping spark and backfiring at the "highest RPM". I've chased the wires from the CAS and the cops all the way back to the computer and they all look good with good connections. I have a track weekend starting in 24-hours, wtf else can I try?

If the tach on your dash is dropping down, but not on the MS its a problem with the coils

I'm definitely losing spark/power/bang-fire. The event also kills the log.

do you have stock coils/ignitor to test?

I lack an ingniter...unless I can use one from a 1.8.

What are the chances that something is screwed up in the computer?

Wirelessly posted

Any chance I could modify dwell settings? I don't have access to a pesonal computer ATM.

what is it at now? optimal would be 2.5ms running on a MS-I.

I just have a feeling one or more of your cops is bad.

Wirelessly posted

I replaced all 4 of them last night, again. I have a box of 16-Toyota coils, lol.

Wirelessly posted

I wonder if te dielectric grease could have warmed up and dropped down to cause a short to the head like my window switch? I thunk it's going to be a long night.