Cold start misfires

dzenno · 03-09-2010, 06:30 PM

I've had cold start misfires for a while now and the car is in service being looked at but the last few days that the weather was above 0 celsius (above 32F) car wasn't misfiring in the morning and I thought this may have been the reason

BUT

I remembered that I actually ran the car with leaded race gas last weekend (don't worry, i've got no cats on my exhaust line and o2 sensors won't get damaged beyond use from 2 gallons of leaded race gas)...

I'm on original spark plugs (waiting on the bmw spark plug socket to arrive and then i'll replace them) at 37k miles (60k km) and the car was misfiring regularly every morning on cyl 1-3...dealer already replaced coils on cyl 2 and 3 as at the time it was misfiring on 2 and 3 only...

The question is could it be that leaded race gas (vp116) has done something that would cause cold start misfires to go away? Now that this happened, I seem to recall that this happened before as well (misfires going away after 2-3 gallons of race gas)

OpenFlash · 03-09-2010, 07:01 PM

If anything, running your car hard (dyno testing a race gas map) might have cleaned off your plugs a bit. But that's a stretch. Other than that, running leaded race gas should usually have the opposite effect. Definitely time to change your plugs. I'm sure the misfire will come back if you give it a few more changes at start-up.

Shiv

03-09-2010, 06:30 PM	#1
dzenno Banned 273 Rep 5,876 Posts Drives: Join Date: Feb 2006 iTrader: (1)	Cold start misfires - gone after running race gas?? I've had cold start misfires for a while now and the car is in service being looked at but the last few days that the weather was above 0 celsius (above 32F) car wasn't misfiring in the morning and I thought this may have been the reason BUT I remembered that I actually ran the car with leaded race gas last weekend (don't worry, i've got no cats on my exhaust line and o2 sensors won't get damaged beyond use from 2 gallons of leaded race gas)... I'm on original spark plugs (waiting on the bmw spark plug socket to arrive and then i'll replace them) at 37k miles (60k km) and the car was misfiring regularly every morning on cyl 1-3...dealer already replaced coils on cyl 2 and 3 as at the time it was misfiring on 2 and 3 only... The question is could it be that leaded race gas (vp116) has done something that would cause cold start misfires to go away? Now that this happened, I seem to recall that this happened before as well (misfires going away after 2-3 gallons of race gas)
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03-09-2010, 07:01 PM	#2
OpenFlash 1736 Rep 17,960 Posts Drives: A Lot Join Date: Sep 2006 Location: SF Bay, CA iTrader: (0) Garage List 2018 Ducati Panigal ... [0.00] 2016 Mazda CX5 [0.00] 2017 Aprilia Tuono ... [0.00] 2019 BMW M2 Competi ... [0.00] 2015 BMW M5 Competi ... [10.00] 2016 Ducati XDiavel S [0.00] 2016 AMG GT S [0.00] 2011 Ferrari 458 It ... [0.00] 2017 Charger Hellcat [0.00] 2015 KTM Super Duke ... [0.00] 2016 KTM RC390 [0.00]	If anything, running your car hard (dyno testing a race gas map) might have cleaned off your plugs a bit. But that's a stretch. Other than that, running leaded race gas should usually have the opposite effect. Definitely time to change your plugs. I'm sure the misfire will come back if you give it a few more changes at start-up. Shiv
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