the IAC closes at 150F water temp
and IAC flows zero air now and up to 180f+, (if it leaks hot RPM screams hot)
at this moment the engine idles off the bleed and ISC flows hot, (there are no other air supplies... on working system)
rpm of 650 means the ISC is not working, (or list below) (could be it cant handle, gross rich misfiring or lean bogging )
the ECU sets idle at 800 +-50rpm (coded) 650 is wrong , means engine is misfiring or ISC out of control.
and regulates there, hot, (p/s not overloaded or a/c not on, if on? then hot idle is 1000 rpm.
so the duty can be checked with some meters, on DC volts.
and 7v is 50% if that meter works right, most cheap meters don't, but fast meters do , if it can average a 200 hz square wave, and average 0v and 14v to 7v. (50% point) (set to 20vdc scale)
the bleeds screws purpose is not to set rpm, but to put he ISC in its center of authority, once there, idle servo code, wakes up and regulates to 800.
eg; The ISC might raise RPM 400 or lower it, by same,
for example putting the auto stick in drive from park the ecu opens the ISC real wide, to handle that load.
low rpm 650 is caused by
1: egr leaking
2: engine misfire, egr leaks is misfire too. i can hear your engine, so cant hear misfire, and would if it was present.
3: isc dead.
4: throttle tps idle switch stuck open, no 0vdc
if engine runs good on hills its not a CAT melted so, scratch that off list.
16v can also lower RPM out of control for
lean AFR
if the maf is dirty at idle, and say 02 sensor dead.
the AFR goes lean and idle can drop, (ECU tries to prevent it with ISC actions)
or
if you have any air leaks at all from the MAF to the throttle body, same deal or any vacuum leaks at all , it goes lean.
keep in mind the 02 servo (closed loop) works hard to cure lean.
but may not, for 2 reasons
02 dead
or the leak is extreme.
all vacuum lines on engine are suspect.
my 97 had a metal intake top huge pipe.
the mount at the rear was missing a bolt.
and it beat the pipe mount to death cause the alum, mount to break off and huge hole in the pipe, sucking air like mad. or those silly plastic induction pipes crack at the accordion sections.
all induction paths and hoses must be leak free on all MAF engines. MPI.
all leaks are called un-metered air, and are all bad news.
and IAC flows zero air now and up to 180f+, (if it leaks hot RPM screams hot)
at this moment the engine idles off the bleed and ISC flows hot, (there are no other air supplies... on working system)
rpm of 650 means the ISC is not working, (or list below) (could be it cant handle, gross rich misfiring or lean bogging )
the ECU sets idle at 800 +-50rpm (coded) 650 is wrong , means engine is misfiring or ISC out of control.
and regulates there, hot, (p/s not overloaded or a/c not on, if on? then hot idle is 1000 rpm.
so the duty can be checked with some meters, on DC volts.
and 7v is 50% if that meter works right, most cheap meters don't, but fast meters do , if it can average a 200 hz square wave, and average 0v and 14v to 7v. (50% point) (set to 20vdc scale)
the bleeds screws purpose is not to set rpm, but to put he ISC in its center of authority, once there, idle servo code, wakes up and regulates to 800.
eg; The ISC might raise RPM 400 or lower it, by same,
for example putting the auto stick in drive from park the ecu opens the ISC real wide, to handle that load.
low rpm 650 is caused by
1: egr leaking
2: engine misfire, egr leaks is misfire too. i can hear your engine, so cant hear misfire, and would if it was present.
3: isc dead.
4: throttle tps idle switch stuck open, no 0vdc
if engine runs good on hills its not a CAT melted so, scratch that off list.
16v can also lower RPM out of control for
lean AFR
if the maf is dirty at idle, and say 02 sensor dead.
the AFR goes lean and idle can drop, (ECU tries to prevent it with ISC actions)
or
if you have any air leaks at all from the MAF to the throttle body, same deal or any vacuum leaks at all , it goes lean.
keep in mind the 02 servo (closed loop) works hard to cure lean.
but may not, for 2 reasons
02 dead
or the leak is extreme.
all vacuum lines on engine are suspect.
my 97 had a metal intake top huge pipe.
the mount at the rear was missing a bolt.
and it beat the pipe mount to death cause the alum, mount to break off and huge hole in the pipe, sucking air like mad. or those silly plastic induction pipes crack at the accordion sections.
all induction paths and hoses must be leak free on all MAF engines. MPI.
all leaks are called un-metered air, and are all bad news.
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