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Old 08-14-2013, 12:58 AM   #1
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Default 1.6L Miata stumble and hesitation problem

I will try to put the problem simply and then give more details about the specific problem.

At my most recent track event and while driving around the streets my motors feels like it just dies, for a split second, then everything comes back normal.

This mostly happens when full throttle in a straight line and it isn't fuel slosh. The car runs on e-85, with 1000cc injectors a brand new walbro 255 and about 43 psi fuel pressure at idle.

It was tuned and driven on the street and track with no problems. Previously this motor used to cut out randomly at cruise and it did it to me the other night on the street. It also will do it during full throttle pulls at 1.4 bar. The turbo will spool, and it will feel like a limiter almost, It comes on and the motor dies, will surge and try to run, die, come back and die, as long as I keep it floored.

I then tried to datalog the runs.

I'm not hitting boost cut (255 KPA, highest i saw was 241)
My CAS signal looks a little "noisy" (the lines for spark angle are not smooth)
TPS seems to be logging smoothly


Also worth noting, my wideband has been reading lean since the problem happened. I don't know if this is unrelated and my sensor is going bad (I've had problems with my gauge reading wrong in the past (fluctuates sporadically)).

I also read that the CAS controls pulse width of the injectors and maybe that's causing this problem?
My other suspicions are TPS possibly
My idle hasn't been smooth the last couple drives lately either it will lope a couple hundred rpm which is unusual.

Anyways I'm trying to figure this out and I don't think its related to the wiring or a loose sensor but the problem has been inconsistent. Literally in the same day that it will stumble and refuse to accelerate smoothly it made several smooth strong pulls at 1.4bar.

Any ideas?
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Old 08-14-2013, 01:37 AM   #2
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post the logs?
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Old 08-14-2013, 01:41 AM   #3
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It's a long shot , but check to see if the battery tie down has come loose. Mine did and every now and then it would contact the positive terminal and the car would cut out for just a second on heavy acceleration or sharp turns.
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Old 08-14-2013, 01:16 PM   #4
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We know nothing about your car. Help us help you. If you have logs . . . .

Sounds electrical.
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Old 08-14-2013, 08:27 PM   #5
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https://www.miataturbo.net/engine-pe...ered-fc-69770/

That engine. I won't have access to my logs until the weekend because its on a different computer. Ms2 ecu
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Old 08-15-2013, 12:48 PM   #6
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I'd look at the logs to see if the MS is resetting. I was also thinking spark blowout, but I see you have COPS from your thread.

Cool car. You should add a link to your sig.
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Old 08-15-2013, 12:52 PM   #7
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Quote:
255 KPA, highest i saw was 241
you were hitting overboost.
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Old 08-15-2013, 10:42 PM   #8
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Quote:
Originally Posted by hornetball View Post
I'd look at the logs to see if the MS is resetting. I was also thinking spark blowout, but I see you have COPS from your thread.

Cool car. You should add a link to your sig.

It's not blow out because everything stops for a split second.

Quote:
Originally Posted by Braineack View Post
you were hitting overboost.
Is this serious? I set the limit to 255kpa but the log only stated that I got to 241. My gauge never went over 1.4 bar. It was only during full throttle pulls though which is why I'm trying to figure out if it was that vs CAS vs something else.
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Old 08-16-2013, 08:12 AM   #9
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you were 2psi away from target, the MS makes sure you don't hit the limit. is it happening at roughly that peak boost everytime?

make sure not to post a log.
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Old 09-03-2013, 01:29 AM   #10
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ok, I've been trying a number of options and I'm still left stuck.

Here posted are 3 logs and my current tune (lame file names I know)

Labor2 and the one dated for 09_02 are the most recent, 54321 is for earlier reference to problems.

So far, I've put in a new fuel filter, new 02 sensor (same LC-1 that we tuned with), new alternator (140A), new battery, new fuel sock, new CAS.

In boost now, it feels like it's breaking up instead of flat out shutting down at 1.4 bar. Gauge and ECU say 1.4 bar but the car never feels like it goes any faster, turbo spools with almost no effort it seems. Obviously the 02 reading is useless, but we tuned with this LC-1 and everything worked great until recently, the tune is the same as it was when the LC-1 was reading correctly. I don't know why it isn't giving me good values anymore, the wideband gauge pretty much only reads either 21 or flashes 7.4 (max/min values), when I add fuel to the table at idle it starts to acknowledge the reading but still jumps all over the place.

I never re-timed or changed the trigger angle for the CAS. I put it in what looked like very close to the same position as the old CAS.

wastegate spring is 1.4 bar, no boost controller, plugs are gapped to .024 with Toyota COPS, 1000CC inj, e-85.


Any new ideas? It will start to go but in boost it breaks up and cuts out and never starts to pull hard, despite the sensor reading 1.4bar.

If there's more info I can give to be helpful let me know
Attached Files
File Type: msl labor2.msl (88.1 KB, 75 views)
File Type: msl 2013-09-02_10.48.23.msl (206.8 KB, 64 views)
File Type: msl 54321.msl (122.9 KB, 75 views)
File Type: msq best ever burnouts.msq (40.0 KB, 83 views)

Last edited by theshdwconspracy; 09-03-2013 at 01:49 AM.
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Old 09-05-2013, 03:06 AM   #11
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No ideas yet?

I got the wideband to read, I tightened my intake manifold and checked the two couplers I have and it started reading OK.

We timed my car and retarded it a little bit, but now my map is 100% on point again for timing, so it isn't that.

We looked at my logs and we noticed that right around peak boost I get this red line of death through my log and the record says "RESET" and secL starts over again.

Any more ideas? grounds? are there certain grounds for the megasquirt pinout that HAVE to be run to a ground that maybe we missed? The whole car has a brand new harness in it (wired from scratch) so we are thinking maybe we missed an ECU ground? Brain?
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Old 09-05-2013, 08:18 AM   #12
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this MS1?
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Old 09-05-2013, 09:16 AM   #13
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An ms2
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Old 09-05-2013, 10:10 AM   #14
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why are your plugs gapped so low?

This used to be common for guys trying to run stock coils over 15psi, I think the toyota coils will start to break up around 22psi or so, it might be ignition related.
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Old 09-05-2013, 10:12 AM   #15
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pins 1,2 7-19 are all ground. Although MS diagrams shows pin 7 as being a signal ground it states that any of the grounds can in fact be used as a sensor ground. Pins 14-19 on mine all run to the engine block. Pins 1 & 2 I used to ground/shield my CAS.

I don't know how much of this changes for a MS2 vs MS3.





wtf is up with your MAP reading? The readings for the sensors on your log don't make sense.
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Old 09-05-2013, 10:17 AM   #16
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on the v3.0 board, pins 1-2, & 7-19 are all connected to the same ground plane.

oh it even says that right there on your diagram
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Old 09-05-2013, 10:22 AM   #17
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Quote:
Originally Posted by Braineack View Post
on the v3.0 board, pins 1-2, & 7-19 are all connected to the same ground plane.

oh it even says that right there on your diagram
And even the words that I wrote!
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Old 09-05-2013, 10:47 AM   #18
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I had them gapped at .028 and it felt
Like ign blowout. It's 18psi with a to4e

I will double check on the wiring, but we followed the best of the diagrams we could find. The guy who did it had done quite a few cars, but I just wanted to be sure threre wasnt something we were missing. The car ran fine for a few days and 1.5 days at the track but after I got home this problem got worse and worse. Any idea on the ecu reset?

What's wrong with my map reading?
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Old 09-05-2013, 10:55 AM   #19
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again, why are they gapped so low? I'm running 15psi at .040"
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Old 09-05-2013, 10:56 AM   #20
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Well in one of your logs it never goes above 93. If that is kpa than you aren't even making positive pressure. Either that or I'm missing something.
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