cylinder 1 misfire

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Ken Hibbs

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Occasional 301 code, here are the symptoms

2008 V8 110000 miles, replace plugs and 3 coils about a year ago.

Sometimes get a rough idle and misfire after about 2 miles, bad enough that the CE light blinks.

almost always happens when there is a big change and temperature from warm to cold, like 70 degree days to 30's to 40's at night. Once I pulled over, turned it off, the restarted and it didn't return that day. Never happens with the opposite temp swing, that is the morning that it occurs it never happens in the afternoon. Did a couple times in the spring, and now that it is colder, it has happened twice in the past 3 weeks.
 
Sounds like it might be a coil pack again. I replaced all 8 at once after I got tired of trying to determine which one was giving me my issue (I could feel the misfire, but it wasn't enough to set off the CEL or show up in datalogging). After spending lots of time looking at the options and the tons of no-name coils out there for cheap, I bought an 8 pack of Accel coils from Amazon. I think this was back at about 70 or 80k miles. I'm at 121k and haven't felt the misfire again. Plugs were changed at 104k on my V8.



I don't recall which one in Cyl 1 (Driver side?) If so you might check your thermostat housing so see if it's leaking/seeping. If you park facing uphill it may be dripping back down along the head and dropping into the spark plug there in that position. Might be cool enough now that it isn't evaporating out as quickly.
 
With the problem happening with temp change I'd be looking at a vacuum leak on that cylinder that goes away once the engine warms up.
 
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