02 sensors brand new fail (not bad truly, just lies) for any exhaust leaks, (air will suck in there for cracks near by, and engine goes rich. way rich)
im sure yours is ok with low miles... but not sure about cracks.. (scan tool shows 02 stuck at 0v. dead is top clue...)hot
Air leaks near the 02 are unacceptable totally. air is 20% oxygen, and just the smallest amount landing on O2 tips, slams it to 0v. (making it useless)
the mech, said:
" he told me he did the duty cycle in the ECU, not in DLC.."
does that mean? , he has a Tech1 scan tool ?and saw and set the duty turning the bleed? or just looked at it and sees. 90% and thinks that is ok and is not.
Leaks: (isc closed, bleed closed ) what i call test 1.... fails and fails hard, I dont know how to tell you more clearly..
it's not a maybe you have an air leak (vacuum)
it is A a "YOU DO have an air leak."
test 1:
you unplugged the isc elect. connector, this causes it to close 100% (or pinch it, same effect , if not the ISC is stuck open)
then screwed in the bleed 100% , at this time, there is no air supply now, to any new 8v engine, ZERO Air to run.
so it can NOT run with zero air. (impossible and makes test 1 so useful) see why?
so why, is yours running now (test1), answer : not a guess, it has Vacuum air leaks... for sure!
my comment about air and idle above , where its "distraction" only applies to back when the engine ran HUGELY rich.
we fix rich first. not idle ever.... or you or any mech is destracted..
IDLE speeds or DUTY cycle a last step in all repairs, major to the engine. last. never first.
air leaks to the plenum do NOT cause rich.
that is what is detracting. to many. and is why rich is the problem. to cure first.
if spark misfiring is happening then that is first first. (cant burn fuel with no spark or weak, so goes rich. at each misfire, and each misfire cause the O2 to go nuts)
(misfire = lots of raw fuel and lots of oxygen) fooling all 02 sensors. <tricky huh? the ECU does not measure HC, only 02.
if one cylinder misfires. it will send a slug of air (and lots of oxygen) to the 02, and it will read wrong.
PVC only keeps the engine from leaking oil like mad. with it clogged, crank case pressures can rise high ,causing oil leaks sometimes..
the engine will run ok with it clogged, but if the hose is cracked the air sucks in and races at idle.
your ISC is not clogged, it's new.
but pinching the hose, showed, lots of air flowing, from illegal sources.
this is a fact and 2x that if the bleed was closed down. CW.
test 1: HOT ENGINE.
ISC UNPUGGED, OR AIR HOSE PINCHED, i DO BOTH, SEE THEY ARE SAME.
THEN SCREW IN THE BLEED CW.
ENGINE MUST STALL.
THERE IS NO AIR TO RUN THE ENGINE,
NOW.
ZERO AIR...NOW.. TO BURN FUEL, PLENUM VACUUM CAN HIT 27 OR MORE INCHES HG, JUST AS IT STALLS, (ZERO AIR DOES JUST THAT)
OR ABOUT .9 TO 1BAR. VACUUM.
HUGE VACUUM , MAX.
WITH LARGE Plenum air leaks? (that space below the Throttle plate closed 100%) that place the intake valve suck so hard..... and 20"hg vacuum at idle 800.
the ISC gets overwhelmed. with air leaks.
say it's at 50% (with no leaks)
so you add a leak (with a hose pulled (vac) (seen with a duty meter)
the duty % drops. more and more, as you add small leaks of air.
then it hits 0% and the ISC has lost control ! ( cant close any more, ... is why)
and now idle speeds jump above 800 (lost control), and more RPM for each leak added.
same with pinching the ISC hose. (an opposite effect)
the duty goes HIGH way high. (ECU does this but iSC is dead now)
this attempts open the iSC and keep idle a 800 rpm , and will fail.
but we close the bleed and at some point the ISC cannot hold 800 rpm and idle speeds drop (we only have 1 air supply now , the bleed)
as the bleed is closed, the idle goes very low, and finally the engine stalls. as all air supplies are gone. (tiny bit from PCV very tiny)
the engine can not run with only PCV air. impossible. (its half air and half exh. fumes , crankcase blow by)
that is the full answer to how it works.
based on 100% = 12vdc to isc full time.
im sure yours is ok with low miles... but not sure about cracks.. (scan tool shows 02 stuck at 0v. dead is top clue...)hot
Air leaks near the 02 are unacceptable totally. air is 20% oxygen, and just the smallest amount landing on O2 tips, slams it to 0v. (making it useless)
the mech, said:
" he told me he did the duty cycle in the ECU, not in DLC.."
does that mean? , he has a Tech1 scan tool ?and saw and set the duty turning the bleed? or just looked at it and sees. 90% and thinks that is ok and is not.
Leaks: (isc closed, bleed closed ) what i call test 1.... fails and fails hard, I dont know how to tell you more clearly..
it's not a maybe you have an air leak (vacuum)
it is A a "YOU DO have an air leak."
test 1:
you unplugged the isc elect. connector, this causes it to close 100% (or pinch it, same effect , if not the ISC is stuck open)
then screwed in the bleed 100% , at this time, there is no air supply now, to any new 8v engine, ZERO Air to run.
so it can NOT run with zero air. (impossible and makes test 1 so useful) see why?
so why, is yours running now (test1), answer : not a guess, it has Vacuum air leaks... for sure!
my comment about air and idle above , where its "distraction" only applies to back when the engine ran HUGELY rich.
we fix rich first. not idle ever.... or you or any mech is destracted..
IDLE speeds or DUTY cycle a last step in all repairs, major to the engine. last. never first.
air leaks to the plenum do NOT cause rich.
that is what is detracting. to many. and is why rich is the problem. to cure first.
if spark misfiring is happening then that is first first. (cant burn fuel with no spark or weak, so goes rich. at each misfire, and each misfire cause the O2 to go nuts)
(misfire = lots of raw fuel and lots of oxygen) fooling all 02 sensors. <tricky huh? the ECU does not measure HC, only 02.
if one cylinder misfires. it will send a slug of air (and lots of oxygen) to the 02, and it will read wrong.
PVC only keeps the engine from leaking oil like mad. with it clogged, crank case pressures can rise high ,causing oil leaks sometimes..
the engine will run ok with it clogged, but if the hose is cracked the air sucks in and races at idle.
your ISC is not clogged, it's new.
but pinching the hose, showed, lots of air flowing, from illegal sources.
this is a fact and 2x that if the bleed was closed down. CW.
test 1: HOT ENGINE.
ISC UNPUGGED, OR AIR HOSE PINCHED, i DO BOTH, SEE THEY ARE SAME.
THEN SCREW IN THE BLEED CW.
ENGINE MUST STALL.
THERE IS NO AIR TO RUN THE ENGINE,
NOW.
ZERO AIR...NOW.. TO BURN FUEL, PLENUM VACUUM CAN HIT 27 OR MORE INCHES HG, JUST AS IT STALLS, (ZERO AIR DOES JUST THAT)
OR ABOUT .9 TO 1BAR. VACUUM.
HUGE VACUUM , MAX.
WITH LARGE Plenum air leaks? (that space below the Throttle plate closed 100%) that place the intake valve suck so hard..... and 20"hg vacuum at idle 800.
the ISC gets overwhelmed. with air leaks.
say it's at 50% (with no leaks)
so you add a leak (with a hose pulled (vac) (seen with a duty meter)
the duty % drops. more and more, as you add small leaks of air.
then it hits 0% and the ISC has lost control ! ( cant close any more, ... is why)
and now idle speeds jump above 800 (lost control), and more RPM for each leak added.
same with pinching the ISC hose. (an opposite effect)
the duty goes HIGH way high. (ECU does this but iSC is dead now)
this attempts open the iSC and keep idle a 800 rpm , and will fail.
but we close the bleed and at some point the ISC cannot hold 800 rpm and idle speeds drop (we only have 1 air supply now , the bleed)
as the bleed is closed, the idle goes very low, and finally the engine stalls. as all air supplies are gone. (tiny bit from PCV very tiny)
the engine can not run with only PCV air. impossible. (its half air and half exh. fumes , crankcase blow by)
that is the full answer to how it works.
based on 100% = 12vdc to isc full time.
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