Throttle Body Air Bleed Screw

[fixkick]

REDUX #1
wrong car, not 93 ,8v it is a 97 16valve
apples and orange max different extreme, the EFI totally different on 16v,  
when starting any post fresh tell what car you have, first, I tried reading your other posts and got max confused,  on 93.... etc.

this is IAC, this works only on cold engine not ISC, cold. this sets all cold idle air flow and is thermal and not electric, and closes at 150F, so if thermostat fails. IAC goes wrong.
not the lack of any air hoses, only the TB ports do air. air input is from the TB air horn internal rim. output is seen below  in blue arrow. see rust  there that is water path.


THERE IS NO COLD RPM IDLE CALIBRATION AT ALL , ON THIS CAR,  ONLY HARD FAILURES OF IAC OR VACUUM LEAKS CAUSE failure or wrong RPM cold.
16valve is  Air Density system with MAF that measure mass of air flow to inject fuel that matches that. air.
8v is speed density system that uses , MAP sensors vacuum baro sensor to mix fuel based on vacuum only.
basics there,
8v races fast on vacuum leaks
16v goes lean vacuum leaks unless engine is cold.
the are OPPOSITES in functions air and fuel. basics
so idle is too high cold. you say ,well how high is too high cold and now cold is it there? at 6AM.???
the above device (ONLY) sets cold rpm. it alone (and sure bleed but bleed is hot only calibration)
cold start on the 16v, all air 99%comes from IAC above. so if cold RPM is too high , IAC is bad or there are vacuum leaks or other causes, (even bad mAF)

cold start this engine is rich on PURPOSE to allow cat to warm up fast and go CLEAN. fast.
that means if there is a vacuum leak COLD and you add more air , cold  the RPM will go too high  but how high is your RPM COLD not told 1500 is par but is wide range 1000 to  2000 is my guess;  the wax Pellet seen above SHRINKS more cold, (wax does that) and the valve opens more on colder days. (6AM is max cold , most times) alaska not with standing wild events.

now the bleed screw on the TB up top, my 97 was steel screw and plastic dust cap on top of it.

the bleed screw is for hot only use.
the bleed screw is to set only hot duty cycle, to 50%  across the 2 electric pins of the ISC , electric idle valve HOT only. 180F

to set it easy is uses  needle voltmeter, (old school works best never a DMM unless the DMM has DUTY cycle mode)
we then do this. in short the 96 FSM free book cover this in forum page #1 sticky post.#1.

1: hot engine. 180f to 200f ever below 150f, above it must be or IAC will not be closed wrecking the calibration steps.
2: TPS idle switch pin at 0vdc not 5vdc or the TPS must be calibrated first. (on new cars  all this junk is now automatic with vastly smarter faster PCM)
3: idling engine measure battery voltage first,.  see 14vdc the divide by 2, and get 7vdc, hold that number in your mind or what you read.
4: now put the needle class, voltmeter on the 2 pins of the ISC (back probed with machanics needle probes)
5: adjust the bleed screw for 7vdc.

on  scope we see see a 200HZ square wave in ISC pins and set the bleed to 50%
5mS low and 5mS high and 10mS period on the scope this is the modulation signal to the ISC\
ECU sets HOT RPM NOT YOU only IT does.
all you do  is control its dynamic range and 50% is perfect. this page is cold not hot, but is accurate for signal.
https://fixkick.com/IDLE-AIR/Slide_Show/...ge_35.html




the trouble with 16v and IAC is testing it can be a MAX PAIN DEAL BUT>>>>>>
TB off car in hot pan of water yes (test for closures 100% at above 150F. blow with lips and  rubber hose to ports.


on car super hard to  test  but....
unbolting it like I did above, even snaps the bolts off, rusted. and never good that. a horror that.

but yeah this.. test does work.   (I wonder how many 24 year old IAC are there still good?) my guess damn few.

what  I do is block the IAC ports, at the TB front air horn rim on a hot engine only
IS use thick clean on the rectange horn port (suction) and if restarting the engine rmp hot is good, the IAC IS BAD (at 180f) if at 150 F or lower the thermastat is bad.
or that water hose is clogged to the IAC and the ICA never sees 180f water temp full at all.


here is my page that does that

see the bleed here
https://fixkick.com/IDLE-AIR/Slide_Show/...ge_30.html

see the port suction IAC here
first off the TV must be 99.9999% closed. for sure key off. closed. .0005" gap only if not it was Molested by goons.
the IAC suck port is there.
if you block it on a hot engine RPM does not change but if RPM does change
the IAC is stuck open (bad) or water temps to it are WRONG (bad thermostat or hose to IAC water blockage)









I have the TV blocked open with a 1/4-20 bolt stuffed inside, for better lighting effects.


sorry for long post but  these engines that have many calibration steps. in order.
and are old and most cars this old have 10 things wrong or things messed with wrong, or wrong parts on the car.
THE TV closed is first see the never touch screw, and the paint put on in the TB mfg  final step ?


if the IAC passes tests
we make sure the ISC closes, fully and is not jammed. cleaned with TB cleaner is best,

then vacuum leaks is next. and is very complex this path. nature abhors a vacuum(means on earth only) and loves  find cracks to suck air, nature is not fun here.
even simple gaskets crack or hoses
or the injector rubber cushions leak like mad.  (bottom of injectors) bad and sucks air like MAD.

this ISC can in fact (ecu) adjust for small leaks,. but they tend to add up, or get worse things that leak do that. cracks widen. entropy happens











[url=https://fixkick.com/IDLE-AIR/Slide_Show/images/16v_IAC_w1.jpg][/url]