Rebuilt ECU, now low idle

[fixkick]

I'm assuming the dashpot isnt working due to not high idle for 15 secs.
But il try and get someone over so I can do the 2 person test. When the m/t ecu was in it would crank up idle to say 1500 or so stay there for 15-20 secs then go slowly go down to normal idle.

the DP lasts from 5-15seconds all ECU math on coolant temps (ECT sensed).  colder the engine the longer the fast idle,  for this short run device, (seconds)
the IAC is 100% thermal device, and takes a long time to get 150F water temp.   this device is not ECU controlled at all, it is pure thermal device , in the the base of the TB,  a cold engine this device if open letting in air ,  for about 1500 RPM cold idle.  (active for a long time.  lets say the water temp is 60F and you start the engine, and the engine warms up, the IAC closes at 150F and for sure 180F (thermostat does the 180F regulation)
the 1500 rpm walks down to a point that the ISC (electric) takes over. at 800rpm. +-50rpm (750 to 850Rpm is spec hot RPM all ISC controlled (+ECU runs this device)
that is how it works.
if the MT can not run the DP, the the transistor is bad in the MT, tha DOES THAT.  (isc DRIVER) TRANSISTOR Q100 RUNS THE ISC IF ISC IS DEAD, and not jammed with gunk as most are this old, the Q100 is bad.
https://fixkick.com/ECU/transistors.html

this is my transistor bad page on the 56Bxx series ECU (usa only)

you skipped test #1 , the ONE PERSOn test.
1: open hood. key in pocket, engine off.
2: look at DP plunger it holds the TV open, with its plunger rod, it holds it open say 0.016" they all do this parked, and stays like that for up to 15 seconds started..
look closely, or use vacuum tool test the diaphragm in the DP, make sure it even works at all.  do the diaphragm leak down test, we do to all diaphragm vacuum devices on all cars.  (cold start fast idle device, DP, is extended by default , key off)

learn that fixing one problem of 5 can un mask other problems.  (one hides the other, is very very common on any car with EFI 28 years old)
on newer cars OBD2 tests are not even done until lower order failures (DTC) are cured first. so are even more complex. (hiding rule)
The next test and next device is MR. IAC, it is #1 device, of cold start air supply and cold idle.  
can 2 wrongs make a right,, sure can in electronics, (casual looking) if the ISC is bad and stuck open you dont know the BAD IAC is there, see?
or old ECU has bad ISC port hiding the fact that the IAC is dead. 2 wrongs = right.  see?   life is full of surprises, looking deeper, (peeling the onion)
what will be , will be....

iAC tests....

the IAC is here.  inside the TB throttle body. " Idle AIR controller" thermal,, (look ma' no ECU)
it is open at all times cold. cold water.   the colder it gets the more open it is, and at 150F it closed and stays closed up to 180F
all data below is MINE this is my work to learn what it does, with a way to measure the distance (#60 drill set shanks used)
using 3 tests cases.  a refrigerator 40f (next to milk ) and -10F freeze (next to steak) and hot water pan, on stove. tests.  I did 3 tests.
the gaps are learned using number drills as feeler gauge. see? checked on 2 cars that ran 100% perfect and no failures  of any kind.


SUzuki has no dreams of this lasting 3 decades, 10 maybe, 20 with luck but 30?
[img] https://fixkick.com/sensors/sensor-icons...ermo1w.jpg[/img]


maybe the other MT ecu has failures too, that hide other failures, like DP and ISC.
we use tools to learn this, it is not ever easy, lacking new spare parts,  used parts can be bad.  there are no new ECU now. zero.
we test the DP at its VSV for proper operation, then check IAC is open, one can blow air in to its air ports and see if they flow air cold.
sure can.


the IAC sucks here from here.
all do. cold,,  we learned all this buying used parts bad,  then we learn to test that on all used parts and if good , we win. (used parts must be tested)
 

the other hole that sucks air for IAC is here (in my slide show TB) as you can see this is harder to do air horn and upper body of TB removed



IAC can fail stuck open or closed,  many do stick open and hot RPM is like 3000 RPM or more.  lots do after 3 decades. if not now soon.
all FALSE leaks cause too fast idle not too low like yours.

TV = throttle valve of fly plate as in Butterfly plate (engineering term latter)

the bottom photo AIR port IAC is for IAC and the bleed air screw, both, so I close the bleed screw counting turns till closed writing that down on paper and then test for air flown in hand, (lips to port) cleaned,  the later put the bleed screw back, to its correct setting, (factory)
the air bleed screw is here this is ISC calibration screw for 50% setting.,.  




this topic is about lack of start up and cold idle air supply.  all cars made now do this, same thing using similar devices, ISC for sure)
most cars use  single valve now, that runs hot and cold air supply (idle air) and is smarter and faster and has no need for this IAC thing nor bleed screw.
the smarted cars (ECU) alto calibrate the TPS, and ISC,  look ma' no screws to fiddle, on new cars and no spark timing either, fixed.
this is the dark ages of ECU, old slow dumb and the mech needs to be smarter  and work harder to solve problems, in fact most shops will refuse to work on cars this old. due to all the above.

good luck find what is wrong.
PS:
Most these cars this old , in 1 hours of labor and testing is see 5 things wrong, some can be very hard to cure lacking SUzuki parts,  many are not sold now. new.
at all.
Suzuki went bankrupt here and in canada. log ago, do not sell cars a all here. USA.
Toyota parts do not fit, not these key parts.

is your ecu refurb , from ebay or top car store from CARDONE 1,  rebuilt the latter is prime the former is a joke.

some fleabay sellers think a refurb is dust off.  they grab it dust it off and sell it as  refurb, ( BS)