first off setting idle is the last on the list of all things to fix , tune or correct.
and if you have illegal leaks now, they will only get worse, and setting idle speed (duty) is just chasing the tail. (like catching a monkey)
(imagine 4 leaking injector cushions.... they will get worse)
My comment on 600 is when you have no way to set Duty Cycle (tools). it's a shade tree fix. (ball parking it)
if the scan tool works right, you can set DC with it.
I have the Tech1 page for that here, see all those PIDS?
http://www.fixkick.com/ECU/Tech1/full_scan2.html
see parameter 17? that is DC, i think, im no expert on obd1 scans, i have no tools for this. they are very very rare here. in the USA. most tech1 are now lost ,or broken....here....
but in theory you could set the duty cycle DC with this, PID 17, the number in the box is how far open the ISC , is now.
In theory you could close the bleed, screw, and hit 50% (the number there is the error in RPM and the ECUs correction via ISC dutycycle. ) at 50% the ISC pulses at 0.0025 seconds. 1/2 way.
so lets say you close the bleed 100% oops cant hit 50%
so you find air leaks. and fix them. I blocking all normal paths lets you find the abnormal paths, (normal are a,b,c,d) per my drawing.
NO scope, no Duty meter, no scan tool way. next. my goofy 600 hack.
Shade tree way:
unplug the elect line, if the isc works ok? "trust"?, (closes) or pinch the tube air if , unsure. (keep in mind, old bad ISC can in fact leak)
if you pinch it, you effectively kill all air to the engine,
why?
(IAC is proved not to leak hot ,first), TV is not stuck open with crap or cable set too tight , leaving only one supply of air left the bleed.
my engine drops to 400 rpm it the iSC pinched, some may stall..... depends on the totality of air leaks. and engine health , new engines, can idle real slow, not old.
id do that tests, all the a,b,c,d tests, see my intake drawing there, and all air paths,
you can prove they are all closing, and prove that there are other illegal air leaks, easy.
good, having a real scan tool, is very good idea. closed loop is a goal, as is the long term fuel trim.
Scan tool.
1: does the 02 work?
2: does it hold closed loop status at idle.?
3: if yes, then what is LTFT. ? +40 , -40% or near zero ,, ideal is about -5% (this means the FAM runs a touch rich, and the 02 , servo pulls out -5% fuel to compensate)
if say the injector cushions, or the booster leaked air, the reading would be like +20 to +40.
the reading are POLAR, they can add fuel or subtract fuel,
modern cars use % , some other old cars and these old sidekicks use a binary scale.
parameter 13 long.
0 lean, 128 perfect, 255 rich.
the fsm shows 118 is normal, for hot closed loop. idle.
i think lean means it was rich actual and the ECU went 118 leaner. (tricky huh)?
what is the RPM hot, with each path proven to be blocked, a,b,c,d.... ?????
keep in mind, the LTFT will warn you of fresh air leaks (unmetered air , buy going + xx % )
and that DUTY cycle way off warns of illegal metered air , leaking, by GOING LOW.
low duty is sign of , leaks , a,b,c,d paths.
high + LTFT is a sign of, fresh air from any place. the ECU adds fuel to illegal leaks, until it gets out of control, the bogs.
metererd leaks do not upset, fuel balance. only way high RPM, if the ISC loses control at 0% (0 means im closed)
I adjusted the fuel air and everything seemed to be working ok
what does that mean? you touched what?
ill do a duty cycle session, with scan tool
i see, closed loop fail. bam, idle means nothing now, AFR is BROKEN. fix that first.
ok , my o2 was bad (pretend,) or the exh crack made it lie, i fixed that and CL , is true , at idle. Closed LOOP is CL flag a binary single bit.
CL =ture
I look at LTFT its at -5% that is a good sign but mine is +30% oops, that is bad. (its adding huge fuel)
so this is a classic sign of a huge air leak. (or even a weak MAF) the ECU dont know why , it only know what the 02 servo loop shows. its lean.
I have and atmospheric leak, not a stuck open isc or TV stuck open or the bleed set wrong, this is REAL air, called UNMETERED AIR.
I test my MAF carefully , i clean it and its showing the correct grams /sec, at idle. (its not the maf)
so I uses any of the 5 ways to find air leaks. (liquid fuel spray, water, propane, or smoke machine, or total dismantling & inspection'ouch")
the can happen from the trailing edge of the MAF all the way to the intake valves in the head.
all seals, all gaskets, are suspect,
1: i find the brake booster hose , when pinched, or blocked, solves the huge LTFT offset. sure, its bad.(diaphram crack)
2: the injector cushions died long ago. and leak air.
3: my 1997 the rear of that huge , alumin. induction tube. mount , in the rear, not seen was broken off and the casting had a huge air hole in it. sucking illegal air all the time. bam.
4: the intake boots are bad. cracked. (the huge AIR pipe main Induction to air cleaner +MAF)
5: intake gaskets bad.
6: TB gasket bad.
7: a vacuum hose somewhere is cracked, many.
now only DUTY Cycle is way off, not 50% (LTFT is normal)
A: SET WRONG.
B. TV STUCK OPEN OR or someone fiddled that factory screws, on TB , bad boy.
C: the bleed is unscrewed 100% or missing.
D: the IAC leaks. air, hot. or the hot water never makes it through its guts.... oops, bad water flow.
E: the ISC is leaking, the rubber ring looks like the moons surface, "craters" so i recal it ,using my Barnyard ways, i set the no touchscrew so the cone just does close it. 99%
i correct those then set the bleed, hot, CL, at 50%, im done. the ECU sets RPM not me, i can only change the DUTY.
and if you have illegal leaks now, they will only get worse, and setting idle speed (duty) is just chasing the tail. (like catching a monkey)
(imagine 4 leaking injector cushions.... they will get worse)
My comment on 600 is when you have no way to set Duty Cycle (tools). it's a shade tree fix. (ball parking it)
if the scan tool works right, you can set DC with it.
I have the Tech1 page for that here, see all those PIDS?
http://www.fixkick.com/ECU/Tech1/full_scan2.html
see parameter 17? that is DC, i think, im no expert on obd1 scans, i have no tools for this. they are very very rare here. in the USA. most tech1 are now lost ,or broken....here....
but in theory you could set the duty cycle DC with this, PID 17, the number in the box is how far open the ISC , is now.
In theory you could close the bleed, screw, and hit 50% (the number there is the error in RPM and the ECUs correction via ISC dutycycle. ) at 50% the ISC pulses at 0.0025 seconds. 1/2 way.
so lets say you close the bleed 100% oops cant hit 50%
so you find air leaks. and fix them. I blocking all normal paths lets you find the abnormal paths, (normal are a,b,c,d) per my drawing.
NO scope, no Duty meter, no scan tool way. next. my goofy 600 hack.
Shade tree way:
unplug the elect line, if the isc works ok? "trust"?, (closes) or pinch the tube air if , unsure. (keep in mind, old bad ISC can in fact leak)
if you pinch it, you effectively kill all air to the engine,
why?
(IAC is proved not to leak hot ,first), TV is not stuck open with crap or cable set too tight , leaving only one supply of air left the bleed.
my engine drops to 400 rpm it the iSC pinched, some may stall..... depends on the totality of air leaks. and engine health , new engines, can idle real slow, not old.
id do that tests, all the a,b,c,d tests, see my intake drawing there, and all air paths,
you can prove they are all closing, and prove that there are other illegal air leaks, easy.
good, having a real scan tool, is very good idea. closed loop is a goal, as is the long term fuel trim.
Scan tool.
1: does the 02 work?
2: does it hold closed loop status at idle.?
3: if yes, then what is LTFT. ? +40 , -40% or near zero ,, ideal is about -5% (this means the FAM runs a touch rich, and the 02 , servo pulls out -5% fuel to compensate)
if say the injector cushions, or the booster leaked air, the reading would be like +20 to +40.
the reading are POLAR, they can add fuel or subtract fuel,
modern cars use % , some other old cars and these old sidekicks use a binary scale.
parameter 13 long.
0 lean, 128 perfect, 255 rich.
the fsm shows 118 is normal, for hot closed loop. idle.
i think lean means it was rich actual and the ECU went 118 leaner. (tricky huh)?
what is the RPM hot, with each path proven to be blocked, a,b,c,d.... ?????
keep in mind, the LTFT will warn you of fresh air leaks (unmetered air , buy going + xx % )
and that DUTY cycle way off warns of illegal metered air , leaking, by GOING LOW.
low duty is sign of , leaks , a,b,c,d paths.
high + LTFT is a sign of, fresh air from any place. the ECU adds fuel to illegal leaks, until it gets out of control, the bogs.
metererd leaks do not upset, fuel balance. only way high RPM, if the ISC loses control at 0% (0 means im closed)
I adjusted the fuel air and everything seemed to be working ok
what does that mean? you touched what?
ill do a duty cycle session, with scan tool
i see, closed loop fail. bam, idle means nothing now, AFR is BROKEN. fix that first.
ok , my o2 was bad (pretend,) or the exh crack made it lie, i fixed that and CL , is true , at idle. Closed LOOP is CL flag a binary single bit.
CL =ture
I look at LTFT its at -5% that is a good sign but mine is +30% oops, that is bad. (its adding huge fuel)
so this is a classic sign of a huge air leak. (or even a weak MAF) the ECU dont know why , it only know what the 02 servo loop shows. its lean.
I have and atmospheric leak, not a stuck open isc or TV stuck open or the bleed set wrong, this is REAL air, called UNMETERED AIR.
I test my MAF carefully , i clean it and its showing the correct grams /sec, at idle. (its not the maf)
so I uses any of the 5 ways to find air leaks. (liquid fuel spray, water, propane, or smoke machine, or total dismantling & inspection'ouch")
the can happen from the trailing edge of the MAF all the way to the intake valves in the head.
all seals, all gaskets, are suspect,
1: i find the brake booster hose , when pinched, or blocked, solves the huge LTFT offset. sure, its bad.(diaphram crack)
2: the injector cushions died long ago. and leak air.
3: my 1997 the rear of that huge , alumin. induction tube. mount , in the rear, not seen was broken off and the casting had a huge air hole in it. sucking illegal air all the time. bam.
4: the intake boots are bad. cracked. (the huge AIR pipe main Induction to air cleaner +MAF)
5: intake gaskets bad.
6: TB gasket bad.
7: a vacuum hose somewhere is cracked, many.
now only DUTY Cycle is way off, not 50% (LTFT is normal)
A: SET WRONG.
B. TV STUCK OPEN OR or someone fiddled that factory screws, on TB , bad boy.
C: the bleed is unscrewed 100% or missing.
D: the IAC leaks. air, hot. or the hot water never makes it through its guts.... oops, bad water flow.
E: the ISC is leaking, the rubber ring looks like the moons surface, "craters" so i recal it ,using my Barnyard ways, i set the no touchscrew so the cone just does close it. 99%
i correct those then set the bleed, hot, CL, at 50%, im done. the ECU sets RPM not me, i can only change the DUTY.
http://www.fixkick.com