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Logging missfire


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Yea I seem to develop a miss only when the engine is hot, and only under high boost (18psi) on e85. By hot I mean after some hard driving for some time. No DTC are logged. Have replaced plugs in the past with bkr7e gapped to 0.7mm which seems to fix it for a few thousand KMs(2000kms) but eventually comes back. Just tried regapping standard iridiums today which seems to be driving ok. But obviously logging individual cylinder missfire would narrow it down a lot quicker

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iridium will be better. Copper don't last long enough. Also drop the gap lower to 0.6 with a proper tool (or pay them to do it for you) 

How rich are you running? This will make the spark more likely to "blow out". 

Also coils, are they originals? 

I suspect you will be getting a random miss on any of the 6.

Do you have a photo of the old plugs? 

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I'm far from an expert here but from the black ones I pull out at 220,000kms they look brand new in comparison. 

0.78 is quite rich but without a wideband it's anyones guess. I would definitely confirm the afr. Will cost you $50 to get someone to weld a bung in your dump pipe and you can set it up permanently. Make sure it's 11 o clock so no moisture sits in it, also at least 30cm from the turbo so you don't cook it. 

How much timing are you running at peak torque and redline? If it's conservative you could lean it out and see how it goes. 

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  • 4 years later...
On 2/3/2019 at 3:35 PM, Roland@pcmtec said:

They do a misfire test and will log a Dtc if it occurs. This will only pick up a severe consistent miss on the same cylinder though. We might be able to log the actual values used though. 

Are you trying to diagnose a specific problem? 

Does the pcm do anything during a misfire under load?

Or is it just guess the mechanical problem game 

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