Redtruck-VA
05-11-2011, 07:05 PM
Some of the folks with cams install get the "Misfire Code". I came across this in the manual and it might help understanding what is causing the code. I was curious as to how the PCM determined if the engine misfired as I couldn't figure out what parameter it was watching to determine a misfire. Turns out to be somewhat over simpilfied, the PCM detemines the engine misfired by watching the the crank speed sensor. If it changes speed outside a predetermined amount it is considered a misfire.
If a cam lopes it may very well cause a misfire code.
MISFIRE MONITOR
Excessive engine misfire results in increased catalyst
temperature and causes an increase in HC emissions.
Severe misfires could cause catalyst damage.
To prevent catalytic convertor damage, the PCM
monitors engine misfire.
The Powertrain Control Module (PCM) monitors
for misfire during most engine operating conditions
(positive torque) by looking at changes in the crankshaft
speed. If a misfire occurs the speed of the
crankshaft will vary more than normal.
If a cam lopes it may very well cause a misfire code.
MISFIRE MONITOR
Excessive engine misfire results in increased catalyst
temperature and causes an increase in HC emissions.
Severe misfires could cause catalyst damage.
To prevent catalytic convertor damage, the PCM
monitors engine misfire.
The Powertrain Control Module (PCM) monitors
for misfire during most engine operating conditions
(positive torque) by looking at changes in the crankshaft
speed. If a misfire occurs the speed of the
crankshaft will vary more than normal.