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Old 05-12-2016, 12:12 PM   #1
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Default Low RPM misfire

I will upload a log here shortly once I do one but here is a general overview of the car

Ms2e
Fm big spark kit
Fresh plugs

Started a few weeks ago as a rare miss, pulling out of parking lots in 1st gear would stumble a bit and then pick back up. Fast forward to now:

Standing in traffic or just driving around town and trying to move, it will misfire around 2000-3000rpm and then be fine. Soon as I shift to the next gear it starts missing again and sometimes will clear itself up and other times will keep sputtering. If I just romp on it in 3rd gear or higher it still pulls great. Misses during light load and low rpm.

Put in fresh spark plugs and no change. Tuner told me to try driving with TPS unplugged, no change. Tuner told me to disconnect my o2 gauge from its harness to try and turn off the sensor, no change. I tried to swap out my coil packs but the FM location is such a PITA that lots of swearing and cut knuckles later I got nowhere with removing the old stuff.

So in short, what could cause these misfires down low at low load but not up high in boost? I do have Singular louvres that sit over a few connections, which I took apart and saw no water in. AFR during misfire dips to 16:1-17:1 range. Normally I am around 14-15 just cruising around down. Sometimes I can feel it start missing at idle and watch the AFR dip, then it will steady itself back out.

Hopefully the log later will help. Just posting now to see if anyone has ideas off the top of their head. Log will be up by 2pm today
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Old 05-12-2016, 01:41 PM   #2
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Default

Quote:
Originally Posted by Mazdaspeeder View Post
I will upload a log here shortly once I do one but here is a general overview of the car

Ms2e
Fm big spark kit
Fresh plugs

Started a few weeks ago as a rare miss, pulling out of parking lots in 1st gear would stumble a bit and then pick back up. Fast forward to now:

Standing in traffic or just driving around town and trying to move, it will misfire around 2000-3000rpm and then be fine. Soon as I shift to the next gear it starts missing again and sometimes will clear itself up and other times will keep sputtering. If I just romp on it in 3rd gear or higher it still pulls great. Misses during light load and low rpm.

Put in fresh spark plugs and no change. Tuner told me to try driving with TPS unplugged, no change. Tuner told me to disconnect my o2 gauge from its harness to try and turn off the sensor, no change. I tried to swap out my coil packs but the FM location is such a PITA that lots of swearing and cut knuckles later I got nowhere with removing the old stuff.

So in short, what could cause these misfires down low at low load but not up high in boost? I do have Singular louvres that sit over a few connections, which I took apart and saw no water in. AFR during misfire dips to 16:1-17:1 range. Normally I am around 14-15 just cruising around down. Sometimes I can feel it start missing at idle and watch the AFR dip, then it will steady itself back out.

Hopefully the log later will help. Just posting now to see if anyone has ideas off the top of their head. Log will be up by 2pm today
I'll upload logs soon but when we went out it decided not to misfire. The only thing I noticed before we went to log was that the db9 cable had come out of the back of the Megasquirt box. I doubt that had anything to do with it though but who knows. Leaving mechanic now, if it starts missing again on the way to work I'll be pissed.

My next step would be to check the coil packs individually. Then maybe I'll try wetting the louvres to see if it comes back with water. Really bummed the logging was kind of a waste
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