POP when turning ignition on (not cranking) and burned fuel smell - Page 5 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 12-04-2008, 02:31 PM   #81
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Flood clear mode this can be set in "More Cranking Stuff" Sometimes you might want to temporarily stop the injectors from injecting fuel during cranking to clear a flooded engine. This is achieved by holding down the gas pedal during cranking. The MegaSquirt needs to know at what point of gas pedal deflection it should turn off the injectors and a good starting point would be just before floored.
To get this value, go to Tools, Calibrate TPS, and push the gas pedal almost all the way to the floor - about where you think the fuel should be cut off and hit Get Current. Remember this value and hit CANCEL on the Calibrate TPS dialog. Insert this value for the TPS Flood Clear. If this value is set too low then you will not get any fuel during cranking. If you set this value too high, then you won't be able to press the pedal enough to trigger the Flood Clear.
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Old 12-04-2008, 03:02 PM   #82
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Originally Posted by Braineack View Post
Sometimes you might want to temporarily stop the injectors from injecting fuel during cranking to clear a flooded engine.
Good advice. But I think this is an answer to a separate problem.

Iím not trying to stop the injectors from injecting fuel during cranking. Iím trying to stop the single spark event at power-up. If that single bastard spark is eliminated, so would be the cold-start pop. Momentary spark interrupt could solve this, yes?
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Old 12-04-2008, 03:13 PM   #83
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fix your leaky injector.
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Old 12-05-2008, 07:51 AM   #84
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fix your leaky injector.
I don't think it's a leaky injector, mine does this sometimes too, had my injectors tested, they don't leak, period. I still get an intake backfire occasionally
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Old 12-05-2008, 10:26 AM   #85
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tested by whom? I am starting to doubt the practices of IR. Gonna send mine to Witchhunter or Cruzin Performance from now on.
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Old 12-05-2008, 06:28 PM   #86
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tested by whom? I am starting to doubt the practices of IR. Gonna send mine to Witchhunter or Cruzin Performance from now on.
An Injector cleaning company in the UK ASNU Fuel Injector cleaning by post..
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Old 12-05-2008, 06:52 PM   #87
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I don't think it's a leaky injector, mine does this sometimes too, had my injectors tested, they don't leak, period. I still get an intake backfire occasionally
What's your guess, then?
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Old 12-07-2008, 03:37 PM   #88
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What's your guess, then?
it's a 'feature'
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Old 04-03-2009, 04:36 AM   #89
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After reading through this thread, it doesn't appear that anyone figured this out.

So this just started happening to me. Started happening after I went turbo. I installed my 550s and ran them for a couple of weeks without this happening. Not sure if they're related. There is seemingly no ryme or reason to the pops except that it doesn't happen if I rev the engine and kill it at like 3k.

Also along with this, sometimes my car does not crank on the first try. It does like half a crank and stops as if something is in the way. Injectors are 550s cleaned and flow tested by injector rehab.

I am running fairly rich right now...perhaps way too rich? At about 13:1 afr at idle.
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Old 04-03-2009, 04:56 AM   #90
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I get this on rare occasion. Maybe once every 50 starts. Always cold. Twice it's been big enough to foul a plug; car ran like crap for 30 seconds then came back normally.
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Old 04-03-2009, 04:59 AM   #91
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I get this on rare occasion. Maybe once every 50 starts. Always cold. Twice it's been big enough to foul a plug; car ran like crap for 30 seconds then came back normally.
I'm curious if this might have something to do with me jumping FP and GND instead of running the fuel pump wire off the MS.

And I notice this plug fouling thing too. Totally runs like crap for a few seconds.
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Old 04-03-2009, 05:06 AM   #92
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Also along with this, sometimes my car does not crank on the first try. It does like half a crank and stops as if something is in the way.
too much fuel in cranking settings.
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Old 04-03-2009, 05:17 AM   #93
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I don't understand this either. I get it now the weather warming it seems, can be anything between parked for 3 hours and a couple of days. Fouls a plus sometimes indeed.

We need to figure this out dammit.
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Old 04-03-2009, 05:19 AM   #94
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Originally Posted by richyvrlimited View Post
too much fuel in cranking settings.
That would make sense, just loaded a new msq not long ago and didn't change my cranking settings. I will investigate this tomorrow.

As for the popping, no fracking clue. It startles me when it happens, then it smells like someone lit several matches.
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Old 04-09-2009, 05:58 PM   #95
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I had this happen while I was calibrating an o2 sensor and gauge. I had to power up the LC-1 and XD16 a couple of times and when it popped the engine didn't rotate. I assumed it was fuel vapor leaking into the exhaust from an open valve and being ignited in the pipe by the hot o2 sensor.
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Old 04-09-2009, 06:19 PM   #96
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Quote:
Originally Posted by JohnW8 View Post
I had this happen while I was calibrating an o2 sensor and gauge. I had to power up the LC-1 and XD16 a couple of times and when it popped the engine didn't rotate. I assumed it was fuel vapor leaking into the exhaust from an open valve and being ignited in the pipe by the hot o2 sensor.
+1, My car didn't start this until I installed a WB with a heated sensor.
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Old 04-09-2009, 06:33 PM   #97
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Quote:
Originally Posted by wayne_curr View Post
After reading through this thread, it doesn't appear that anyone figured this out.
Not figured out? We know that the MS, when configured as we do, sparks the plugs at initial powerup. So either fuel remains in one or more chambers at shutdown due to the engine not rotating through a full cycle to clear it, or a small mount of fuel drips out of the injectors and finds its way into one or more chambers after shutdown.

Quote:
Originally Posted by wayne_curr View Post
(...) it doesn't happen if I rev the engine and kill it at like 3k.
Which suggests that in your case it is due to the engine not rotating through a full cycle after you shut it off, thus leaving some fuel in one or more of the chambers (said fuel having been injected on the last squirt prior to shutdown) which subsequently ignites.



Quote:
Originally Posted by richyvrlimited View Post
too much fuel in cranking settings.
Cranking fuel has nothing to do with this. The pop in question occurs before cranking begins.



Quote:
Originally Posted by JohnW8 View Post
I had this happen while I was calibrating an o2 sensor and gauge. I had to power up the LC-1 and XD16 a couple of times and when it popped the engine didn't rotate.
Every time you powered it up, the MS squirted priming fuel. If you didn't crank it, that fuel stayed behind and drifted into whichever chamber had open intake valves. Then you turned it off, and then when you turned it on again, pop.



I don't see why this is such a mystery. If you want to make it stop, either make sure that the engine turns a full cycle (two rotations) at shutdown (add rotating mass, or blip the throttle before you turn the key), or wire your spark outputs to be inverted so there's no spark at powerup.

Last edited by Joe Perez; 04-10-2009 at 10:16 AM. Reason: fixed quote tag
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Old 04-09-2009, 08:20 PM   #98
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Ok, it still does it even if I rev the engine a bit before shutdown. I must be dealing with leaky injector(s) issue(s). I dont have a light flywheel or anything and my idle is high to begin with so i'm pretty sure its getting 2 revolutions before shut down even if I dont blip the throttle before killing it.

As long as the pop isn't damaging anything, i'm fine with it. The only adverse effect I seem to be dealing with are fouled plugs making the car a bitch to start sometimes (runs on 3 cyls til the plug comes back to life).

Just swapped out the plugs with some bkr7e's and gapped them to .025. We'll see what happens I suppose.

Quick question: Are leaky injectors due to the injectors themselves being rebuilt improperly, or due to a poor installation by myself? Or are RX7 550s just kinda leaky and shitty to begin with?
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Old 04-10-2009, 11:03 AM   #99
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I had brand new RC 550s installed by a pro, so unless that **** is know to leak I doubt it's that. Joe's explaination about inverted outputs seems correct. The fouling is the only issue I have with it.
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Old 04-10-2009, 11:40 AM   #100
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i still et this occasionally as well. i don't understand what you mean by making the engine go a full cycle after turning it off, how are you supposed to do that? by hand?

the problem is that ms fires the plugs when turned on, is there any good reason for it to do this?
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