I had this problem with my Autronic SMC
in my case it was leaking Injectors
WOLF 3D V500 ECU getting engine sneezes when turning key
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- Russellb
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WOLF 3D V500 ECU getting engine sneezes when turning key
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- Steampunk
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WOLF 3D V500 ECU getting engine sneezes when turning key
My car never did this before, but over the last couple of weeks it has done it 3 times.
The repeatability is, as you mentioned, cranking immediately after it has failed to start on it's previous crank attempt, ie. within 10 seconds, and igniting unburnt Air-fuel mixture.
It must cause the coils to ignite even on the "ON" position, I can't think of anything else that can cause the engine to kick.
Scared the bejeebus out of me the first time it did it.
I don't think it's harmful though.
The repeatability is, as you mentioned, cranking immediately after it has failed to start on it's previous crank attempt, ie. within 10 seconds, and igniting unburnt Air-fuel mixture.
It must cause the coils to ignite even on the "ON" position, I can't think of anything else that can cause the engine to kick.
Scared the bejeebus out of me the first time it did it.
I don't think it's harmful though.

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WOLF 3D V500 ECU getting engine sneezes when turning key
Russellb wrote:I had this problem with my Autronic SMC
in my case it was leaking Injectors
Yeah that's what I was thinking too or perhaps the injectors have started firing before the engine has cranked.
If you had access to a car like this, would you take it back right away? Neither would I.
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WOLF 3D V500 ECU getting engine sneezes when turning key
I literally just read a thread on this while googling for some info on injectors... It seems that some ecu's will fire an injector or two when the ecu is powered up and if you have a leaky injector or injector seal thing that it sits in, there can be enough fuel vapour in the cylinder to ignite. They were talking about changing some delay setting in the ecu, though that thread was about Link ecu's
- timk
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WOLF 3D V500 ECU getting engine sneezes when turning key
Some ECUs have a "fuel priming pulse" setting that needs to be disabled. My supercharged NA with a MegaSquirt had this enabled and the pressure from the combustion (the sneeze noise) blew the crossover tube off into the plastic radiator top tank and cracked it open!!
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