1.6 8v

[lasthunt]

okay so i have done some research both on the truck and on your tech pages , I must say you have done a excellent job describing the mech functions of all the specific equipment so much that it has left my feeble brain somewhat overloaded to a certain extent.anyway it looks like the PO has installed a motor or at least the intake and throttle body from a auto truck, even the ecu from  serial list you provided confirms this . is this a issue as i am running a samurai manual transmission? trucks runs okay although it has a high idle which i will start trouble shooting using your directions on the tech pages. i do have a spare ecu from a 89 manual truck i could swap out if needed

swaps are not easy.
in then end you must make the ECU happy.
the 89/90 had 3 way idle up pin, too.  via 3 way diode "OR" logic module, that needs to be addressed(happy)
so the 90 harness off the A/T car donor is there,  i bet yes and the harness is A/T and the PRNDL switch is gone and connector just dangling under car?
the A/T things to forget are PTC heater, it is only and output device . (A/T ECU)
the A/T has TCC relay now abondoned, that is ok.
what maters are all inputs to that ECU. for  sure all things that can do fast idle.
in 1990 what are those.?

Head lamps on,
Blower on, (cab heater blower on)
AC on, if old donor had AC it has AC amp and that will tell ECU to idle up to 1000 rpm IIRc 920 is  spec then, not 800. hot. normal.
Defrost rear glass , idles up if present.
PS power sterring over load too. idles up .
hot idle up modes. lots on gen1 kicks, (head lamps is the shocker no?)
what about DRL  if in canada by law DRL, is required, and it too turns  on running lamps . Day light running lamps.  best is defeat it if can. easy really.
The ECU if it detects (non in park/neutral) goes to very aggressive idle profiles.  this is to the A/C clutch dragging in say DRIVE.
how this agressive pans out , IDK
also your car is M/T so has clutch and i bet the clutch switch is missing so the ECU does not know that path of logic, similar to the PRNDL.
there is 5th gear switch too that if missing will confuse any ECU.


All inputs to the ECU must be checked, first before fiddling with IAC or ISC. or duty cycle.
some of these cars are frankenkicked with custom main ECU harness. IDK yours?

ok so you have the A42 ecu. a/t gotcha. ! (it can be made to work even if jumper'ing it (lies) to make it happy in MT car. my 91 was.

good luck to  you!
harness was removed from a donor truck by the look of it,
i have installed my manual ECU and the truck starts i have not taken it out for a test run yet very soon though 
fyi and a heads up i am picking up a 94 supposedly a low miles 1.6 8v with harness and ecu next week im thinking of installing after the hunting season this year , i would think i might have a few questions on the engine controls ....
 

added a picture of the truck