Hitachi E coil update....
04-25-2007, 04:34 PM
#11
I don't think the misfires are coilpack faults. ..
The fact that all of the cylinders are experiencing misfires, at the same time, indicates that either there is a fuel quality problem, or the common power supply to the coilpacks is intermittent. I will venture a reasoned guess and suggest that there is a fuel supply/quality problem responsible for the misfires.
Background info:
The misfire event DTC, is recognized by the ECU, when the angular velocity of the crankshaft varies outside of the range occurring during a normal 4 stroke cycle sequence. IE, during the time interval in question, the crankshaft slows down momentarily, more than it should, accelerating again with the next power stoke. Even when the engine is running perfect, the crankshaft angular velocity is constantly increasing and decreasing, plotted on a X-Y graph, the angular velocity (Y axis) looks like a sign wave, rising and falling with a regular period with Time(X axis).
Therefore, a misfire DTC, does not result from the ECU monitoring the ignition system directly, it does that indirectly, by monitoring crankshaft angular velocity. The conditions setting the misfire DTC can be caused by fuel or mechanical problems that prevent proper ignition.
It is unlikely that all of the coilpacks are defective, so it follows that there is something else common with all the cylinders involved with the misfires, like fuel quality or quantity. In addition, at cold start, fuel mixtures are not uniform and are near the lean ignition limit already, any insult to the fuel will worsen this issue, and increase the prevalence of fuel ratios varying between cycles, that can be too lean for ignition to occur reliably.
Background info:
The misfire event DTC, is recognized by the ECU, when the angular velocity of the crankshaft varies outside of the range occurring during a normal 4 stroke cycle sequence. IE, during the time interval in question, the crankshaft slows down momentarily, more than it should, accelerating again with the next power stoke. Even when the engine is running perfect, the crankshaft angular velocity is constantly increasing and decreasing, plotted on a X-Y graph, the angular velocity (Y axis) looks like a sign wave, rising and falling with a regular period with Time(X axis).
Therefore, a misfire DTC, does not result from the ECU monitoring the ignition system directly, it does that indirectly, by monitoring crankshaft angular velocity. The conditions setting the misfire DTC can be caused by fuel or mechanical problems that prevent proper ignition.
It is unlikely that all of the coilpacks are defective, so it follows that there is something else common with all the cylinders involved with the misfires, like fuel quality or quantity. In addition, at cold start, fuel mixtures are not uniform and are near the lean ignition limit already, any insult to the fuel will worsen this issue, and increase the prevalence of fuel ratios varying between cycles, that can be too lean for ignition to occur reliably.
04-25-2007, 04:49 PM
#12
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i blew a coilpack and my CEL just flashed under load..
CEL never stayed lit. went about 1.5 miles in 15 minutes (gotta love the city) and just had a cylinder 4 misfire upper limit exceeded.
how come my CEL didn't stay lit?
how come my CEL didn't stay lit?
you can see my post earlier 
04-25-2007, 05:16 PM
#16
Any determination identifying the source of the problem, involves a process of elimination.
That requires each possible cause be checked and confirmed if involved as the cause or not, starting with the most likely, progressing to the least likely as needed. I missed you post about this earlier, what is the link?
04-25-2007, 05:23 PM
#17
Several options are available, but the easiest, and least expensive, is replacing..
the fuel in the tank with some known good quality gas, and examining any drained fuel for water. Although, defective gas can have issues other than water. Get fresh gas from a different supply chain, if possible. With fresh gas, drive the car like you stole it for a few miles, to "blow it's nose" so to speak, and see how it behaves for the next few days.
04-25-2007, 06:34 PM
#19
As cylinder 3 is involved in both "events", the first with #2, then with the 1,2, and 4,
and now alone, try swapping coilpacks in cylinders 1 and 3, and see if the most actively misfiring cylinder moves to #1.
At this time, one thing I can offer for sure, is the situation at this point, is unclear.
At this time, one thing I can offer for sure, is the situation at this point, is unclear.
