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944 cold start issues


PORSCHE951

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The problem happens when reving at idle or driving under load. Honestly cant remember the peak voltage of the signal however I know it was more then the arming voltage, constant strong signal that never dropped out. I also dropped the arming voltage to as low as 1.5v across all rpm range and the problem still existed... Should probably mention the crank sensor has been replaced and gapped properly due to the old one being damaged from previously touching the flywheel/ reluctor teeth. (The problem has existed before and after sensor replacement).

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I have had a sensor touch the trigger wheel and get chewed by about 2mm -it had come loose at Kyalami-. Still worked perfectly but changed it out for new.

Not sure of your trigger setup but if it helps, mine was loosing the sync at about 7k.Just garbled info to the ecu and would cut dead.Tracked it down to a too small a trigger plate within the 360 sweep.ie: signal was marginal to start off with and then was lost.

Simon suggested a 180 deg "raised lump/trigger" on the cam and that solved my problem.

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Yeah I can try. I'll take the car into my work Wednesday and scope the crank signal again with the Snap-on Modis.

I'd like to make this work rather then using an alternate trigger wheel... especially since the wave form would remain flawless on the Modis screen even when errors were counting at ~4800 rpm and the engine was missing.

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  • 2 weeks later...

So I scoped the crank sensors and monitored them at idle and high rpm and did not see any drop outs.. had a problem uploading the scope data to the cpu so all I have is a lame pic of the triggers at idle. I did make a log and monitor it where I found the dwell time is cutting out when my misfire happens while trigger 1 and trigger 2 voltage and signals remain ok. also noticed a limits flags word 1024 which displays shortly before and after the misfire / ign cut event... no idea what that means.

I tried to upload the log but it says the extension llg is not allowed?

post-1679-143450215695_thumb.jpg

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