Idle speed not raising on heat or headlights

[fixkick]

here is the FSM factory service manual. 1page on top, no idea me what GEO is bucking facts.
Geo i guess flubs up and uses 1990 facts not real per below. 
when you buy the  ECU from GM/GEO the same exact SIDEKICK ECU is handed to you. So this below is fact.

It’s a Geo Tracker, vin 2CNBJ18U0M.  Spark plugs are new.  T stat is new, not overheating.  I am wondering if it is stuck in limphome mode or ISC stuck? It’s an on road vehicle. Nothing crazy,  been acting like this since I’ve owned it several years.  Heater is load/lights are load/steering is load.  Dips to about 500 and holds there.  If I turn off lights and heater and go for a drive, it will idle normal after. As soon as heater or lights come on, RPM drop. If steering wheel is turned left or right at idle, rpm drop.

Great some great facts and evidence.    
you skipped the CEL Lamp in the cluster,  key on, glows, turns off running , all cars in the USA 1998 to now same thing the CEL lamp (aka. SES/.MIL)

that is correct on any stock car (battery not bad)
I told you max alernator load is 50amps ,or 600 watts or 0.8 Horse power,  no sorry he electrical loads on this engine never over that mighty 1HP limit ever, Impossible.;

loads are
1: steering overload, but newer with tires out of lock to lock (max CW or MAX CCW ) turned, only at end forced very hard by your hands does the idle up switch trip if EVER.
2: headlamps. are 100watts only and all other lamps in car 100more watts,
3: no elect. load in this car can exceed 600watts or 1 horse power from engine, all else comes from MR. battery and it alone. beyond 600watts. so is NOT THE PROBLEM EVER HERE.
4: this is no 4speed power sucking automatic here with huge clutch load, your car 5speed stick and it in neutral so zero load there.
5: what else, the rear defogger option use the most power of all and again can NEVER overload suzuki.. ever. if yes the fuse blows in all cases.
6: the BLOWER IS max 12 amps>?or  144watts,  no why on earth can it overload any engine, (the exception is below, and next but is a lie really read on)

key fact told finally.  #1 top clue.
as soon as heater or lights come on, RPM drop.  Means engine is weak or ISC dead and or in limphome mode the ECU , CEL lamp still not told by you. sad really this is. why skip this?
isteering wheel is turned left or right at idle, rpm drop.  (well I can only guess your not into to the 2 steering stops of the steering knuckles , right?)

if the engine misfires all engine made produce less power, like 80HP new, is now 40 or less, if 1 cylinder for 4 misfires,  HP is now 60HP or in fact less, drawing any dead piston  around.

so back to square one I have just 2 questions.

KEY ON , CEL lamp glows, check engine lamp. glows not cranked just key ON. yes/no/
then start the engine the lamp must go out, yes/ no./

when CEL glow running that means something vary bad is wrong,  it means scan me or use the DIAGNOSTIC jumper see if code 12 or error codes now.  (same on same year toyota and gee all cars made)

the code tells you sensor X is dead. 50 codes there are. EGR code 51 is very common but all others are super serious hard errors.

these bad codes means ECU is stuck on limphome mode, just like new cars do to, all do.  at failures.
LIMP means
in no order
huge wasted fuel.
engine runs rich and misfires.
no idle speed controls NOW .
no closed loop 02.
spark is grossly retarded means more wasted fuel more rich and more misfiring.
the CAT overheats.
and more , I will stop here,  LIMPHOME IS BAD BAD place to be....

my page here shows how to do the DIAGNOSTIC jumper 89-95,   96 up need scan tool only