89/90 sidekick idle speeds 800/920rpm

[spiritofr]

Fixkick, I'm getting 0Vdc on the ISC pins and I've backprobed both sides of the connector while connected, I even pierced the wires with the needle probes to make sure I was touching metal, and I tried two different DMM's at 20Vdc. What do you think is going on? My idle seems pretty good and stable, always 750-850, and 900-1000 with accessories on. Earlier this week I turned the TB screw until 800rpm and calibrated the TPS with 0.086" gap (5 gauges stacked) turned to 250-350ohms, the throttle feels pretty good. I recently cleaned the EGR and installed a new fuel pump so the car starts great on first crank when cold, RPM goes to 1800-2000 for a few seconds then quickly down to 1500-1600 and then very slowly down to 800 so I assume the dashpot, IAC, and temperature sensor are working.

Thanks for your help!

[fixkick]

yes, the dutycycle is a factory tool (a current meter of some kind , a suzuki secret)
but any scope does this easy, (child's play really seeing the wave form there) turn throttle stop till it goes 50% (half high , half low; done)
with DMM they are not all the same, vast designs of DMM inside, make things harder. ( i always try)
using the DC scale.
some show 7volts at 50% real well.
what is key is this.
the faster DMM work best, (not long slow 1second sample rates) it need to be 2 times or more faster than 0.005 seconds, say .002 seconds for faster samples....we need to digitize the ups and downs.... see?
some DMM have filter that blocks AC signals, (fails) some are just blind to A.C signals on DC range. (Filters inside, etc)
others report peak DC only.
others report the average of DC samples. (bingo)
when the average of 14.7v is at 50 % it reads 1/2 that.
but all this is tedium,, just connect up and see if it works. if you see like 6v, and you turn the bleed (91+) or on early kicks turn the throttle stop and can get 7v , all is good.
it it shows 0v or 12v or 14v all the time, try another dmm. or is not responsive to idle air changes.

when done and at 50% the engine will never lose control of idle ever.
in park or drive, or all accessories ON, or all things loading engine or none.

---

it helps to have 4 hands,
2 for needles
and 2 more to fiddle DMM ...
my bud calls this jiggery pokery.... funny that..

[zukitrek]

Ok Fix. thanks for showing the how to. Will let you know.

Cheers!!

[fixkick]

one more way
the analog voltmeter with needle might work more easy.
one more thing to try, $10 at walmart, in cars and in the electrics isle too.

[spiritofr]

Thanks Fixkick, this helps a lot!

But besides duty cycle, how do I know the ISC is getting any power? You said the blue/black to red wire on the connector is 12v, and the green/black to green is ground, but when I probe just the blue/black or red I don't even see 12v, it shows 0v, does this mean the ISC is not getting power?