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?

post the logs?

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.

We know nothing about your car. Help us help you. If you have logs . . . .

Sounds electrical.

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

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.

you were hitting overboost.

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

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.

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.

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

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?

this MS1?

An ms2

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.

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.

https://www.miataturbo.net/attachmen...ine=1378386769



wtf is up with your MAP reading? The readings for the sensors on your log don't make sense.

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! :D

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?

again, why are they gapped so low? I'm running 15psi at .040"

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.

what's your O2 in? voltage? you're hitting 0v? what's that like 7.3:1 AFR?

that with your small gap, you're blowing out.


I feel like you need to calibrate your TPS too.

Il try to post a better log tonight. I recalibrated tps, got the 02 reading again, notice it only goes to 21 or 7.4, and my map goes to 200+ in all my logs when I've looked

so are you or are you not at 7.3:1 AFR (0.02v) in boost?

Not, afr are roughly 11:1 in boost

Hrmm.. wtf is up with my viewer.. this is what I see: Max: 93

https://www.miataturbo.net/attachmen...ine=1378421727

Two new logs.

That log you are looking at is correct, these two are hopefully more telling of what's going on.

I'm literally down to: fuel injectors (clogged), and grounds. If someone has another idea, let me know. I honestly don't know where to go from here.

I had the timing locked at 10* for the first log and that time it pulled better until ~1bar.

I decided to only post one map.
First strange issue, when we first tuned the car, the duty cycle of the injectors maxes out at maybe 75% DC. During this log it hits 99% which isn't correct. I checked the injector screens, but they looked clean. I cleaned them more anyways.


Notice when scrolling through the time line, it says record 500 of 887 and if you advance "frame" by frame, it counts up. At record 534 it's fine and at record 536 it's fine. Where record 535 should be is says MARK 003 RESET.

So, why is my ECU doing that? I cleaned up my current grounds so hopefully they look/work better.

After that I'm out of ideas.

I dont have MLV here, but that above screen shot. That spike in PW is not cool, do you have trigger happy accel enrichments?

here's a picture of it. There is a red line straight through everything (where the blue line is currently) where the record says RESET

have you tried to open the gap up to at least .035"

also, why so retarded ignition timing?

and isnt' 11:1 like super rich considering e85?

Tuning issues aside, it ran well like this for a number of days and then all of a sudden stopped working.

That's a little rich, we tuned it to be around 11.5-12:1
Plugs are still closed up (should I try iridiums?)
My friend has been tuning SRs forever so this is probably based on his experience with those, which I know aren't Miata motors. How much more can I run safely? Trying not to max my cylinder pressures because of how fragile those rods are said to be

Just a thought . . .:

Do any of your outputs go to relay coils? I've had these types of resets before and they were caused by flyback voltage. If that's the culprit, there are several ways to address the problem.

We added 3 more grounds to 7-19. We resoldered any connections on the board that might have been questionable, I put in .032" plugs (brand new) and still got resets. I took one run with .024" gaps after the soldering and I had no resets just break up. So I thought maybe te gap suggestion was right, but it reset again with bigger gap. We are thinking mate the coil drivers are overheating and causing a shut down? We just reduced the dwell but haven't had time to test yet. We are thinking maybe these drivers are weak/dying so if this doesn't fix it I was planning on replacing those and going to a 4 bar map sensor just for the extra room since I am nearly maxing this sensor out.

Reducing dwell didn't help

I think you should listen to braineack and go into the Acceleration Wizard and set map threshold to 500 and/or the tps threshold to 4.9v. See if that helps. It has with me multiple times when a TPS wire was grounding out occasionally.

I've tried everything anyone has suggested to this point. I seriously have no clue anymore. This isn't a check your plug gap kind of problem though. For some reason the ecu resets and the log shows a reset condition several times during the course of every pull at 1.4 bar. It's only resetting at full boost not rpm related. The log and data show this

Have you tried increasing your over-boost setting?

ExtraEFI.co.uk HOME

Tuning Your MegaSquirt-II™ (or MicroSquirt®)

Are you guys fucking joking?

I think I might have a similar problem so hope that some ideas come forward from this thread.

Car runs perfectly 99% except at high load/boost in 4th, 5th and 6th when it momentarily hesitates (feels just like the rev limiter sometimes, others a lot softer version), the AFR spikes to 16-18 for a split second then car keeps going.

I think the AFR spike is a side effect not the cause.

I also get random resets in my logs, which I believe occur at he same time...

Does this sound similar...?

Also, did you click the MS2 tuning link?

It provides good info on grounding issues which I haven't ruled out as part or total cause of my issues....

AFR will spike anytime there is a misfire for any reason because O2 is present. Definitely a side effect.

That sounds like boost cut. This is a hard shit down/hesitation and if I keep flooring it it just keeps resetting.

Car used to pull hard until the reset but now it breaks up then resets so it's a decaying problem that has gotten worse over time

Unplug the TPS and try it

I'm very hopeful for the above two suggestions of unplugging the TPS and upping the boost cut.

An uneducated thought occurred to me, have you considered a faulty or randomly failing coil or perhaps your wiring to the C.O.P.S..?

I tried loading new firmware but couldn't get it to work. New coil drivers and map sensor are on the way. Tomorrow those will get installed, I will unplug the tps and try again. If that doesnt work I will replace the cops, I have a full extra set and have been trying them as I go, not scientifically. Next step after that is to ohm the wiring harness to check for loose wires/resistance. (The whole harness is brand new high grade wiring, engine harness uses an automotive grade bulkhead connector, all crimp connected with brand new connectors to each sensor.)

Like I said, everything did work, so something in the system must have failed

So, I installed a new map sensor (map daddy 4 bar) in the ECU and loaded new firmware (MS1 029). I rebuilt my old map and the car won't idle. Do I need to retune because it's a new map sensor or should my settings still be good?

I figured out the problem. Getting AEM, that will fix it. AMIRIGHT?

no.

So I guess here are updates, not that anyone has a clue any more but maybe someone will chime in with something I've missed.

I had two sets of toyota COPS. I put all the original cops back in the car and another GOOD CAS and it worked. briefly. I drove it around town, boosted it (1.4bar), did burnouts and beat on it. Took it to the track, drove 5 laps and it started to reset and break up again.

The original cops are loose and can lose connection by popping out which is why I swapped them out. Soon as I put a new (second set) coil in it would make the problem worse.

It would work for half a lap with the original ones in and then start resetting and stumbling again.

Problems/Solutions

I was having alternator charging issues, the over driven 140A alternator creates a lot of drag and slips if the belt isn't super tight. I've been tightening it to help my problem.


I've also never installed the 10k MFD Capacitor in my system. However I'm not entirely convinced this is my problem, because a week worth of beating on the car (after it was built and tuned) and I didn't have a single problem while tuning or at the track without this Cap. The wiring is all brand new mil-spec.

All my sensor wiring runs through a bulkhead quick disconnect, idk if that is creating any kind of problem, but it is an automotive grade connector and shouldn't cause that kind of problem.


Ideas? I did decide to ditch the Megasquirt (Found out it was an MS1) and I bought an EMS4. I want to make sure that I can fix this problem so that my new ecu turns out to be a worth while purchase, and not an expensive toy in the middle of a headache problem.


Thanks for your help if you read this whole thing