1989 /90 only, Idle speed problems.   G16A  TBI  EFI fuel injected engine  in USA/Canada                    

The ISC system is failing , The Idle Speed Contoller ISC , device.         
Idles too fast or  the ISC will not REGULATE speeds.   (jump to easy way)

This page covers Generation 1 Sidekicks  dash  -60Axx ECU's  never 1991 and newer. Hit the back button for other years.
If you have air leaks, hit the back button, and find them.
Same rules,  the ECU sets idle not you,  it's hard coded to 800 HOT. (acessories off in park or neutral)
What we do is set the duty cycle and the  ECU does idle controls (servo action)

The 1989 and 90 fail for the same exact reasons as say the newer 1991 + do..
This page below is only for dutycycle setting and how to do it better than the poor FSM shows in 1989 below.
This  ISC is  missing parts (hot water to the ISC) early car has more idle up features
The  unique 89/90 features.   These 2 years varies greatly form newer 8v.
Has no air horn (TBI) AIR bleed screw, as all 1991 and newer cars have.
The Throttle body only as 1 adjustable throttle plate stop screw,  to set duty cycle.
Rule1: You must get the idle switch closed first, then set duty cycle, and then LAST set the idle switch using the TPS feeler gauges, This is because the stop screw , changed, causes both to be wrong.
First duty set, then TPS calibration.
ONE EASY CHEAT: (Ignore the TPS for now)

What cures this pain, is to jumper clip, the idle switch, to ground, first.  (forcing the ISC ONLINE Full time, connect the dutymeter to the ISC 2 wires (back probed) set duty to 50% then set the TPS idle switch. (most be done it THAT ORDER)
Once the DUTY is at 50% , we then calibrate the TPS using the TPS mount screws. (follow 89 links)
The early cars 89./90 have extra idle up modes only these 2 years,  A/C on, P/S overload, then adds,  Headlights on and blower and defrost. So if not at 800 rpm idle hot or 800 in DRIVE, then turn off all accessories! to get 800.. First.
Idle up is 920 RPM.
Cold idle is near 1500 (air temperature dictate this not the ECU at all, cold)
This ISC is noted for its getting loose 89/9 , rattling like mad and sticking.  26 years of it beating itself to death , 200 times a second,.

The engine must hold  closed loop status if not it might be too lean run slow or too fast richer . See scan tool oxygen sensor  data here ,see OBD1 section.

The real 89/90 setup lacks a bleed screw. (the  stop screw is the device used to set duty cycle and nothing else)


This  motor and EFI (electronic fuel injection) is unique, to newer models 
Top differences are : Unique ISC ( hard to test) the IDLE UP, DIODE BLOCK and UNIQUE idle spec rules for A/C , Head-Lights and Defrost and FAN turned on.

DUTY CYCLE IDLE CAIBRATION (done before TPS calibration, it must be)
The idle setting procedure from OEM FSM is directly below seen as photos: (Original Equipment Manufacture , Factory Service Manual)
Never use this  page for newer cars 1991 and newer. (go back and hit home above)  SEE FASTER WAY HERE
  1. Hot engine.   180f minimum. (ECT measure 300 ohms (about) unplugged. or scan tool reads 180F min.
  2. Engine runs perfectly, and up to 3 throttle cables are all set slack to Suzuki spec...= 10mm play,  (cables throttle, cruise and A/T kick down cables can stick too and wreck idle)
  3. All accessories OFF (or pull  the diode block, if car has wiring faults to same ! )  The block allows many things to raise idle. (A/C, HL, Defrost,FAN blower (heater))
  4. Air cleaner not dirty.
  5.  If the engine plenum has vacuum leaks all these  steps are useless.  (or IAC in base of TB is stuck open? for ANY REASONS)
  6. If the IAC valve is stuck open , all of this page is just useless words. or  if the engine plenum has vacuum leaks all these  steps are useless.  
  7. Ground the  TPS idle switch  using a ground jump wire and backprobing pin,  4 pin TPS connector pin C,  Blue-white connnected to ground. (this keeps the ISC active under all conditions)
  8. Connect a Duty meter to the ISC pin pair, I use this meter. (costs $25 on ebay and works great)
  9.   FSM States, Raise idle to above 1500 RPM and let it slow down to idle speed (800 RPM)

  10. The Dashpot vacuum device must be fully retracted (it does this automatically in 3 to 30 second (faster hot) but if not , you must tie it back some why, and fix the bad DP later.... ok?
  11. Check that idle is 800 +- 50 RPM  (with Car Tachometer or better hand held optical tachometer.)
  12. ADJUST the throttle stop screw.  to 50% DUTY {never do this, on any newer 91+cars} if you can not reach 50% then YOU HAVE AIR LEAKS IN THE PLENUM.
  13. Wit  any failure of the idle controls hot, do the pinch test here to find the culprit.  or  see this page on the  89/90
  14. The 5 idle up devices to the ECU are falsely sending, Idle up commands, will make setting duty impossibe.
  15. You are done,  at 50% you are, now set the TPS calibration, with jumper above removed.

Calibrate the TPS, last.  but do not touch the throttle stop screw when doing those TPS steps!

If the idle speed race, that means the ISC has lost control.
There are many reasons to race.
Hit the back button, as racing on this engine is the same on all engines.
Short list of causes, (setting duty cycle under these failure modes can be useless)
  1. ISC bad. (most are this old)
  2. IAC stuck open hot.
  3. vacuum  leaks
  4. vacuum hose leaks
  5. vacuum diaphragms on any hose leaking.
  6. ECU in failsafe mode.
  7. DTCs stored, (errors ) found in scan tool or DTC flash codes, a good code is on code 12
  8. Any of 10 gaskets on the plenum or throttle body leaking. (cracked)
  9. ISC gaskets sucking air.
  10. EGR gasket sucking air  or the EGR main body cracked, sucking air.
  11. Spark timing in spec.
  12. Cam timing in spec, (not slipped tiiming belt retarding the cam and spark all at once)
  13. A lean running engine, or misfiring for ANY reasons.
  14. Flooding engine.

Only a fully good and tuned engine will idle correctly. (and allow setting Duty cycle accurately.
Any factors that over tax the ISC will cause the ISC to loose control, even setting the ignition timing, too far OFF, can cause that.
If the ECU can't control idle , It can HUNT the ISC and cause surging. (a stuck Dashpot will cause ECU to HUNT the idle up and down , surging)
 This hunting is a SUZUKI bug, and illegal on todays  cars. Is dangerous to drive any hunting engine.
All engine that are gross lean will hunt naturally, even with the ISC OFFLINE.


After setting DUTY , you need to its check ISC regulation.
On this car when you put on electric loads, the idle raises to 920 RPM.  (via the diode block logic, plug it in, if removed before now.)
Same with A/C.  (Idle rises to 920 RPM)
But putting car in DRIVE , the ISC will hold RPM at 800.

PHOTO REAL #1 Below:  Notice the ISC has no air  hose nor the 2 water heating hoses. (just 2 wires one green) below. ISC is above IAC.

Photo1: Real TBI here, 1989/90.

The 89/90' Throttle valve adjuster is for hot idle only. see red arrows below. 
60Axx ECU's only

The FSM PAGES  1989/90 (only)   , Step 4 below is wrong, I think Suzuki thinks shops down have a duty meter or  nor a tech1 scan tool and can read parameter 17 seen here from FSM books.
Use the below steps only if lacking propert tools like this.
A working ISC will fight you with any changes to that screw.  If the ISC has lost control this screw can in fact bring the ISC back in to ECU control.  (like falling off a cliff, turn in, and in, and bam 800 rpm happens..)

The ECU :
The ECU can not crank or run right or regulate idle with air leaks, stuck air valves or with inputs telling big lies.

The critical pins on the 89/90 -60Axx ECU are:
FAST IDLE COMMAND PINS:  A= Y  B = G , Suzuki to GM pin number changes, colors never  change.
A3 = 0 vdc fast idle from diode module,  (fan,defrost,headlights are on, any or all)
A2 = 0vdc,  A/C is on, activates fast idle mode.
A13= 12v , if 0v your P/S is in  overloaded , fast idle feature
A14 = 0v  the TPS idle switch,  if not 0 then TPS is signalling off idle ,bad TPS or maladjusted.
B12,  0v ,  A/T PRNDL switch signals. only this signals I'm in drive if not 0v.  0 means park or neutral.  This pin if at 12v, cause ecu to NUTS in PARK or Neutral, for sure. (m/T cars this is not used or 0v)
B11, 0v , if not at zero the ECU thinks you are cranking endlessly.  that be real bad.
There are more inputs to mess up the ECU,  the ECT sensor below 180F , IAT reading grossly wrong. MAP sensor way off. and more.  (only a scan tool can see all sensors working, and that all things are ok.)

If running an A/T ECU in a M/T car, make  sure B12  is grounded or at 0v. running.
See the Schematic   here.

ECU PIN LOGIC:   Called an ECU PIN OUT drawing...

Dumb things that can be wrong, usually caused by a mad , or crazed, PO (previous owners):
The TPS can be installed wrong, it can be mis-Indexed. 
See the mount at TPS here?   the TPS must be carefully indexed to the COUPLING or the TPS will jam the throttle open , do not be like a Toyota driver. LOL !
Photo 2: shows how the 1991 IAC really works, and with secret data..... all IACs work this way,  150F rule , the 89/90 IAC is the same.

The above coupling prongs fit to the below. Photo 3:


Next is a real 89./90 body  
Do not fiddle the Dashpot screw below fuel port. unless the 15 second dash pot idle is way too fast. (they all are , it seems to most) just leave it alone or do the DP calibration later.
 The Idle set screw bottom right, really is duty cycle set.
Photo 4: real 1989/90  the dash pot in the photo must be retracted for the stop screw below right can work correctly. (on a running engine it is fully retracted automatically)

The TB has 5 small holes on the bottom base.  all 5 must be blocked with the gasket or the engine will never every run correctly.
On the base there is 1 water port, and 2 air ports.  large. Those ports must not be blocked, use the correct gasket.

  1. Last after idle DUTY CYLE IS SET  perfectly hot,  we do the TPS calibration for idle switch closure. (after removing my above ground test jumper) My $50 scope.
Photo 6:  This is not a hot engine, below but shows the wave from 200Hz. and when the high = low time,  duty is 50% turn the idle stop screw until the 2 traces top and bottom lines are equal distant (time)
The 1989/90 ISC coil measure 6 ohms, and draws about 2 amps. current, never use this ISC on any  1991 or newer car. or boom. happens in the ECU.
The high voltage will be 13.3 to 15v , the Alternator spec. The ECU transistor that drives this is very powerful. The repetition rate does not change, only the duty cycle changes. (a ratio of high to low)

A real duty meter that works. BEST OF BEST. $25 solution that did not exist in 1989.
This meter works 100%    and is only $25 from ebay.  
Jump the TPS idle switch pin to ground.
  • Hot engine!  180F or more, is hot.
  • Diagnostic jumper shows code 12s, no DTC errors stored or live.
  • Idle switch closed, 0 volts D.C. (see jumper)
  • Engine not misfiring,  or running poorly. (setting duty cycle is the last step after an engine tuneup)
  • Using 2 back probes , back-probing(verb) the  ISC connector pins (any polarity works here)
  • The meter , is set to DUTY mode, seen in yellow below.
  • Running at idle, turn the Throttle stop screw until, the meter shows 50%, you are done. "easy  peasy, japanesy"? 
  • If you can not hit 50%, there are air leaks (aka: vacuum leaks) for sure. (or ECU idle up pins in the wrong state of logic see below for 1 example set)

rev 9, 3-4-2013  (revised 12-1-2015)