11-22-2010, 11:20 PM
getfast Wrote:CEL code was showing for O2 sensor, cleared it, it hasn't returned. Slight misfire is at half-throttle from about 1500rpm to 2500rpm. Cleaned out the MAF and the throttle body, those didn't fixit. 50 miles of driving with STP fuel injector cleaner in half a tank didn't fixit (although it does seem to be improving?) Coilpacks look original, the one plug I pulled was a BMW OEM dual-tip dealio but definitely kinda old looking. Probably gonna see about swapping in some known working coilpacks, and new plugs, this week.
Installed new OEM NGK plugs today. The ones in there were worn but not wasted. More importantly there are several ginormous oil leaks from the valve cover gasket, especially down into spark plug holes #1 and #2. Both those plugs were pretty much soaked and sitting in 1/3" deep pools of Wal-Mart 20w50.
Good news: new plugs and related oil cleanup fixed the intermittent misfire.
Bad news: it came right back 12 miles later.
So tomorrow I'm gonna replace that valve cover gasket set, because oil leaking down into the plug tubes isn't good for anything, whether it's got something to do with the misfire or not. And now I'm pretty sure the miss is coilpacks. I think when I changed the plugs (and reversed the coils front to back) I fixed something that then broke again. Hopefully. So, I'm gonna swap in a set of known good coilpacks from another car hopefully tomorrow and see what happens. If that doesn't fixit, I'm stumped... for now.
Filled up today with Shell 93 octane and a can of STP gas treatment, then discovered that the average mpg on the prior tank was 26.4. That was from like 150 miles of Dave commuting and 200 miles of me test-driving in the city and on the highway and fiddling with stuff while it idled and performing a few italian tune-ups. A new Bosch O2 sensor is like $70 and it only has one (unlike my M3/4 which had four and they each cost more than that), but I think I'll wait. 26.4mpg is certainly around normal for one of these, and the CEL still hasn't come back on.
Next up: figuring out the suspension/steering shudder, and figuring out the clutch related noise. Both are annoying but the car is still plenty driveable (I've put ~225 miles on it in ~30 hours.) Stay tuned for details...
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