Cold start quirks, possibly MS related.
 

It happened again today, so I thought I'd ask about it.

1. Turn the key to on, hear a small POP, like a small backfire. Comes from the engine bay somewhere.
2. Try to start engine, motor turns over 1/3 as much, and it sounds like the starter motor isn't engaging
3. After the 2nd or 3rd attempt, the motor will turn over and catch, but then run roughly for about 30 seconds. It will then run fine for the rest of the day.

I have also had issues with the motor turning over, and then ceasing to turn over, like the battery is EXTREMELY low on juice. The car has never failed to start, though, and it is intermittent. Initial spark angle is set at 10 degrees.

Any ideas? The small pop and rough running worries me the most.

see our "cold start ftl" thread. it will lead you to your fix.

betcha you have prime on power up, so that's causing the pop. the odd start is too much fuel being dumped in while cranking.

what are your cranking settings, exactly?

Attachment 215582

Stock internals, stock head, req.fuel is 6.6, 460cc Rx7 injectors.

Daymn, that's what causes it! Mine is more than a pop, the Boost guage blips to 8psi :eek:

if you get a blip on the boost gauge then it's most likely blowing out the intake.

pull your coils and try to recreate, i have a feeling on startup the MS is igniting a spark.


Savington, you gots too much fuel on cranking.

try this:
https://www.miataturbo.net/~web1_bra...king_table.jpg


prime > 0, means it doesn't prime the fuel pump untill it seeings PWs. After 2 means, it takes two seconds before it will prime. Standard prim of 0.0, means I don't need a prime.

I've tuned my PWs for 460cc injectors, working great for me.

those cranking pulses might be a little on the high side for 460's. even with 305's i'm lower than that at 40*, for instance. granted it's a 1.6, but i can't imagine it would need THAT much more fuel to start a 94.

try switching the priming pulse to "standard prime" and make it a low value, below 1. and switch "fire priming pulse" to "after two seconds" since it looks like that seems to be what people have had the best luck with.

then i'd probably use the calculations in the megamanal to calculate some new cranking PW's:

find a datalog with a good idle, and record that PW. subtract 1 from it, divide the result by 4, and then add 1 back in. that should be your 160* value. subtract 1 from that again, and multiply the result by 10, and add the 1 back in, which will give you your -40 value. take the difference between those and divide it by 10, to get a rough increment to scale from 160 to -40 linearly and fill in the rest of the cells.

((idle PW - 1.0) / 4) + 1.0 = hot crank PW value
((hot crank PW - 1.0) * 10) + 1.0 = cold crank PW value
(cold crank - hot crank) / 10 = increment to work up for remaining bins

chances are, that'll produce values a little on the low side. at least, it did for me. i found i had to move the 130 and 160 bins up to a value close to my idle PW to get it to start when hot.

and brain caught me sleeping at the tree...

only by a few minutes, and i gave the abbreviated version.

I like Scott's version better. :bigtu: I'll throw those values into the car and do a start at every coolant temp and datalog them all to see what's up. Thanks Scott.

less work i suppose :gay:

it may not be perfect for you, but it's dead on for me now.




let me know about the pop.

Someone's rockin the Vista.

I tried for a bit, couldn't get that fucker to let my USB>serial adapter to talk to the system, overcontrolling waste of space!

taken me months to get the internal Bluetooth adaptor going, and even now I still can't drag and drop files, it insists on some gay-ass conjoined link file.

the same procedure works flawlessly in XP

Weird. My shit has worked flawlessly from day one with Vista.

vista = colon blow, according to savington...

:eek: next time I feel bunged up I'll boot the fecker back up :bigtu:

Attachment 215570

That is dialed for 100° and up for a 1.8 on 460cc injectors. Brain, your stuff was pretty low, and the car wouldn't start above 130. I guess it's just the difference between 1.6 and 1.8.

I am having EXACTLY the same problems with the same car and 550 rx-7 injectors. When I hear that pop it smells like either a huge electrical arc or exhaust??? It REALLY worries me. Any idea how this could happen with the coils????????

Kyle, post your cranking settings.

(this feels like a bad Bill Murray movie)

The 'pop' is likely nothing to be concerned about, when the MS powers up the ignitor fires a single time, if there is a combustible mixture in the cylinders (like if you just had a failed start attempt and there is fuel in there) then it can ignite if you shortly thereafter power the MS off and back on. It's nothing to be concerned about...