review of facts:
that 1900 is the key number, in that that may be too high, for even a perfect 50% duty cycle to control.
many of theses cars have bad parts this old. and some are even hacked up. (TPS set wrong, idle stop violated, ISC screw violated ,etc)
finding out which is bad is not easy, but i have a rote path that i follow.
I work the 4 paths is legal air.
hot engine tests:
what is RPM with ISC unplugged?
what is RPM with IAC blocked (no change?> the IAC is GOOD)
those 4 legal paths are: (seen in the drawing above clearly, all other paths are illegal, and i will skip PCV as its tiny.)
1- The TV (throttle valve) and TPS is closed signalling Idle is true.
2: the IAC
3: the ISC
4: Bleed.
what i do is block each one by one to see what happens, ??
Begin testing:
what is rpm with bleed screw all the way in. still way too high? OVER 800 IS BAD.
what is RPM with TV 100% closed, (if it looks closed it is. but it must be. 99.9% closed. (gunk behind it holding it open, or throttle cable set wrong?)
what is RPM with IAC blocked, (no change means its not stuck open, ) this valve is closed 100%# hot.
now we are at the ISC (electric):
we can do 2 ISC tests here, pinch the hose (air hose not the hot water hoses) and see if engine near stalls. like 400 rpm is normal pinched
if that fails that, means you have gross intake leaks. (which can change with air temperatures sure)
if that test passes, super low RPM , then the ISC is open for some reason.
so unplug the electric connector to it, it must now CLOSE 100% (some leak tiny amount , that we can adjust for with the bleed)
it must close, if not, it stuck open. if the pinch test passes. see why, i know that?
I know this because the pinch tests blocked all air supply to the engine, in fact the 1 steps above blocked all air to the engine now and must stall.
this is my tricky but easy way to find the air leak sources.
The hunting is just the ECU cycling the ISC to get to 800 rpm (a goal) and can not get there, so just hunts it , it has no other choice,
it just keeps trying.
btw on new cars it dont hunt, it just slams the system to limphome, or if too bad stall the engine,.
on some kicks/Vitara's the ECU just closes the ISC 100% and prays it will close, (varies by year, engine type and country)
once you prove , say, there is an illegal leak to the plenum (large air box behind the TB , throtte body)
then my pinch page finds the cause.
http://www.fixkick.com/IDLE-AIR/leaks/Hi...-List.html
why 15F?
that is the magic temp that causes the 50 % idle duty cycle to lose control.
The ISC can NOT control idle with vary bad air leaks. it can not.
either kind, measured air or unmeasured air.
it can not.
the best place to have the natural idle is 400 to 1200 rpm. 800 is the center point, at 50% duty cycle.
so if you get leaks say, that cause 1201 rpm the ISC cant correct that, because that is outside its COMMAND authority, range.
lets look at this another way, idle is bad.
so you jump in to the FSM and check idle duty cycle, and find its way off and railed. it's out of control, because of leaks.
back in 1995 the Suzuki shops., tech1 tool shows Duty is railed....oops...
The ISC is not for leaks, its for normal conditions, (hot or cold air, , extra accessory loads on the alternator, power steering stiffer cold,etc)
not for air leaks at all.
I use the nature hates vacuum thing.
The plenum is PULLING 19 inches of HG vacuum. and is 1600 CC strong pull. against a closed TV.
it will find leaks easy, if things go wrong.
if the leaks is from direct atomosphere the engine goes lean (slower) but the hot engine EFI will try to correct lean, but may lose that battle too.
the legal leaks are from the MAF. path. those ALL cause RACING.
the legal leaks are ISC stuck open, IAC stuck open, TV stuck open, and bleed unscrewed (open)
if all my tests fail to find the leak cause
that means the plenum is breached. gaskets seals , hoses, or even cracks.
the process of elimination proves that.
conclusion
there are leaks. but the ECU dutycycle hides them until the air temperature is very very cold.
or might be just duty cycle set wrong.
1: iSC hex screw set wrong, its a factory setting.
2: TV set wrong, same deal.
3: bleed set wrong, in the factory the above are already set, so they do the Duty cycle steps in the FSM. they set it to 50% and 800 happens by
magic. that magic is ECU controls.
The fSm shows using a factory tool to set Duty, and is true. and very hard to do, with wrong tools.
what i do is very crude,
hot engine, 800rpm perfect idle (dont prove its right)
i pinch the ISC, if the idle drops only 100 rpm the duty is wrong. 800 to 700. bad.
if it drops to 400 to 500, its right.
the ISC is bipolar, it must be able to drop 400 or add 400 RPM , if it can do that , all is happy/
Quote:only cold air surge (air temp , not engine temp.) only below 15F or so....the magic temp to me, is obvious. the idle speed is too high for the ISC to gain control ( due to air leaks or duty cycle set wrong)
RPM range is 1500-1900 (16v OBD1)
and only after the engine is warmed up fully
that 1900 is the key number, in that that may be too high, for even a perfect 50% duty cycle to control.
many of theses cars have bad parts this old. and some are even hacked up. (TPS set wrong, idle stop violated, ISC screw violated ,etc)
finding out which is bad is not easy, but i have a rote path that i follow.
I work the 4 paths is legal air.
hot engine tests:
what is RPM with ISC unplugged?
what is RPM with IAC blocked (no change?> the IAC is GOOD)
those 4 legal paths are: (seen in the drawing above clearly, all other paths are illegal, and i will skip PCV as its tiny.)
1- The TV (throttle valve) and TPS is closed signalling Idle is true.
2: the IAC
3: the ISC
4: Bleed.
what i do is block each one by one to see what happens, ??
Begin testing:
what is rpm with bleed screw all the way in. still way too high? OVER 800 IS BAD.
what is RPM with TV 100% closed, (if it looks closed it is. but it must be. 99.9% closed. (gunk behind it holding it open, or throttle cable set wrong?)
what is RPM with IAC blocked, (no change means its not stuck open, ) this valve is closed 100%# hot.
now we are at the ISC (electric):
we can do 2 ISC tests here, pinch the hose (air hose not the hot water hoses) and see if engine near stalls. like 400 rpm is normal pinched
if that fails that, means you have gross intake leaks. (which can change with air temperatures sure)
if that test passes, super low RPM , then the ISC is open for some reason.
so unplug the electric connector to it, it must now CLOSE 100% (some leak tiny amount , that we can adjust for with the bleed)
it must close, if not, it stuck open. if the pinch test passes. see why, i know that?
I know this because the pinch tests blocked all air supply to the engine, in fact the 1 steps above blocked all air to the engine now and must stall.
this is my tricky but easy way to find the air leak sources.
The hunting is just the ECU cycling the ISC to get to 800 rpm (a goal) and can not get there, so just hunts it , it has no other choice,
it just keeps trying.
btw on new cars it dont hunt, it just slams the system to limphome, or if too bad stall the engine,.
on some kicks/Vitara's the ECU just closes the ISC 100% and prays it will close, (varies by year, engine type and country)
once you prove , say, there is an illegal leak to the plenum (large air box behind the TB , throtte body)
then my pinch page finds the cause.
http://www.fixkick.com/IDLE-AIR/leaks/Hi...-List.html
why 15F?
that is the magic temp that causes the 50 % idle duty cycle to lose control.
The ISC can NOT control idle with vary bad air leaks. it can not.
either kind, measured air or unmeasured air.
it can not.
the best place to have the natural idle is 400 to 1200 rpm. 800 is the center point, at 50% duty cycle.
so if you get leaks say, that cause 1201 rpm the ISC cant correct that, because that is outside its COMMAND authority, range.
lets look at this another way, idle is bad.
so you jump in to the FSM and check idle duty cycle, and find its way off and railed. it's out of control, because of leaks.
back in 1995 the Suzuki shops., tech1 tool shows Duty is railed....oops...
The ISC is not for leaks, its for normal conditions, (hot or cold air, , extra accessory loads on the alternator, power steering stiffer cold,etc)
not for air leaks at all.
I use the nature hates vacuum thing.
The plenum is PULLING 19 inches of HG vacuum. and is 1600 CC strong pull. against a closed TV.
it will find leaks easy, if things go wrong.
if the leaks is from direct atomosphere the engine goes lean (slower) but the hot engine EFI will try to correct lean, but may lose that battle too.
the legal leaks are from the MAF. path. those ALL cause RACING.
the legal leaks are ISC stuck open, IAC stuck open, TV stuck open, and bleed unscrewed (open)
if all my tests fail to find the leak cause
that means the plenum is breached. gaskets seals , hoses, or even cracks.
the process of elimination proves that.
conclusion
there are leaks. but the ECU dutycycle hides them until the air temperature is very very cold.
or might be just duty cycle set wrong.
1: iSC hex screw set wrong, its a factory setting.
2: TV set wrong, same deal.
3: bleed set wrong, in the factory the above are already set, so they do the Duty cycle steps in the FSM. they set it to 50% and 800 happens by
magic. that magic is ECU controls.
The fSm shows using a factory tool to set Duty, and is true. and very hard to do, with wrong tools.
what i do is very crude,
hot engine, 800rpm perfect idle (dont prove its right)
i pinch the ISC, if the idle drops only 100 rpm the duty is wrong. 800 to 700. bad.
if it drops to 400 to 500, its right.
the ISC is bipolar, it must be able to drop 400 or add 400 RPM , if it can do that , all is happy/
http://www.fixkick.com