BurbMan wrote:
carringb wrote:
A weak coil won't set codes until it completely fails.
That makes sense that the coil won't set a code as long as the PCM detects that it is firing, but if it's weak enough to cause a noticeable driveability issue you would think that the PCM would use its other resources like the O2 sensors to detect incomplete combustion or call it a misfire even if it doesn't know which cylinder..
O2 sensors only measure the air/fuel ratio, and not how complete combustion is, at least not directly. The closest it can get is a "slow response" or "slow switching" code, but that can be triggered by other problems unrelated to the ignition system. In reality, a single misfire will just result in more oxygen present in the exhaust (since it isn't combining with fuel), so it simply adds more fuel to the entire bank.
What the PCM is really looking for is a change in crankshaft velocity. The reason the V10 can't pick up misfires as easy is because there's more cylinders firing per revolution, so the change in crankshaft speed isn't as apparent as smaller V-motors. Its basically less sensitive to a misfire.
