Throttle Body Air Bleed Screw

[Peter Wood]

G'day,

Looking at trying to adjust my idle speed and reading your posts, I found my idle air bleed screw is mangled beyond adjustment, and looks like fully srewed in.  It's some kind of plastic?

I haven't tried to shift it, is there a replacement or workaround?

[fixkick]

G'day,

Looking at trying to adjust my idle speed and reading your posts, I found my idle air bleed screw is mangled beyond adjustment, and looks like fully srewed in.  It's some kind of plastic?

I haven't tried to shift it, is there a replacement or workaround?

1993 8v ,MT.
8 has plastic cap cover (day 1 new) on frong of the TB, throttle body.
once removed cap the screw valve is  steel valve, treads and cone valve inside, like see on old houses, sink water valves (brass) it adjust air flow (bleed) for Duty cycle.
if screwed in fully that is CW, to unscrew it turn CCW.
there is not idle speed adjustment COLD engine  that is the job of IAC, valve on the bottom of the TB. (a thermal valve only based on water temps only) and closes fully at 150F deg.

hot idle speeds are ECU controlled only (based off Engine RPM only)
the bleed screw is to calibrate idle duty cycle of the ISC valve, that the ECU modulates.

if the bleed screw screwed all the way in , is proof that lat person had failng idle speeds and that idle controls are dead.

so idle is racing too fast hot? engine fully warmed up RPM Is 800 +/- 50  RPM  750 to 850RPM is spec, the ISC does that at the commands (modulation) of the ECU.

at hot idle 800
you cam turn on head lamps and heater and the idle holds at 800 and not drop lower RPM and hang low, this is regulation happening via ECU.
rpm raised to 1000
for PS overload, power steering turned in to the rails, hard. or a curb.
A/C turned on or blower.
electric rear glass defroster turned on. 4door car with glass rear and is and option, what car is this you have.

and lots more. I need full symptoms of failure to be accurate.

[fixkick]

i still do not know what car you have, or if you work on 2 kinds
1993 16v
doors 2 or 4 or as in Europe 2 is 3 and 4 is 5 doors.
4wd or 2wd, ?
3,4speed auto tranny. (AT)
5peed stick shift tranny? (MT)
AC or non AC. (factory AIR)
rear glass heater rear glass door? with wire heater in glass called rear Defrost.
got power steering yes some had none, or 4 wheelers love to remove it.
I need to know what car you drive to know how the ECU controls work for sure IDLE.
some cars have a wrong ECU in them and this wrecks IDLE controls for example using AT ECU in MT CAR .

OK found this.
1993 Geo Tracker, 8v, MT (5sp), 4WD, 123K miles (door count) got factory air?AC, got PS? (rag top no rear defrost heater?)

it is not 16v so the bleed screw is center front of TB not top
how many doors on the car. guess 2 doors , as that is mostly true sold in USA , but in canada they had vast variats of trackers , sidekicks and Sun Runners sold.

[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]

[Peter Wood]

i still  do not know what car you have, or if you work on 2 kinds
1993 16v
doors 2 or 4 or as in Europe 2 is 3 and 4 is 5 doors. 
4wd or 2wd,  ?
3,4speed auto tranny. (AT)
5peed stick shift tranny? (MT)
AC or non AC. (factory AIR)
rear glass heater rear glass door? with wire heater in glass called rear Defrost.
got power steering yes some had none, or 4 wheelers love to remove it.
I need to know what car you drive to  know how the ECU controls work for sure IDLE.
some cars have a wrong ECU in them and this wrecks IDLE controls for example using AT ECU in MT CAR .

OK found this.
1993 Geo Tracker, 8v, MT (5sp), 4WD, 123K miles (door count) got factory air?AC, got PS? (rag top no rear defrost heater?)

it is not 16v so the bleed screw is center front of TB not top
how many doors on the car. guess 2 doors , as that is mostly true sold in USA , but in canada they had vast variats of trackers , sidekicks and Sun Runners sold.



1997, 4 door, G16B 16v, auto, 4WD, running a bit fast at cold start.  When it warms up idle drops down, no problem with running aircon when warm.   IAC valve passes the 'pinch test'.

The cold idle, Bleed Air adjustor looks exacty same as yours on your 95 model video.  I think you've answered the question.  The broken up bit I'm seeing is probably just the black plastic cap, it had a Phillips type head that has simply crumbled away.  I can dig that out and I guess I'll find the metal screw below to try to adjust the cold idle. 

Good to hear that the effective screw is steel, further inside the throttle body.

Many thanks!  

[fixkick]

1997, 4 door, G16B 16v, auto, 4WD, running a bit fast at cold start.  (well the IAC does all the cold, and is not 8v, so you have 2 cars? one 1993"?)
what is too fast in RPM? tell that? 1500 is possible
the colder it is at 6am p (sailers say coldest just be for dawn)  the colder it is  the higher the IAC RPM will  the IAC is 100% thermal device, pure mechanics no electrics here)
have you ever owned or driving perfect sidekick/tracker/  or only the 1/2 dead?


When it warms up idle drops down, no problem with running aircon when warm. 
IAC valve passes the 'pinch test'. The 16v engine ,the IAC block is bolted to the Bottom of the TB<
the ISC has no vacuum hose at all just water hose
https://fixkick.com/IDLE-AIR/Slide_Show/...IAC_w1.jpg

I guess you meant ISC this is electric and has water and 1 air hose vacuum.

The cold idle, Bleed Air adjuster looks exact same as yours on your 95 model video.  ( that is 16v)
the 16v is not at all like 8v, your other post show mention of 93 8v. so I got confused, to start  any post here fresh tell what car you have thank you.


I think you've answered the question.  \
The broken up bit I'm seeing is probably just the black plastic cap, it had a Phillips type head that has simply crumbled away.  I can dig that out and I guess I'll find the metal screw below to try to adjust the cold idle.
what is on your 97 for a cap or screew I do not know, suzuki for sure put in tons of plastic in 1998 even the intake huge air pipe went plastic
and gee cars this old have vast engine swaps, so what is under your hood, is anyones guess lacking photos

wow 97 so I will delete my first post or edit it max.

again the BLEED screw is for hot engine only, and is not any kind of idle speed adjustment at all.

it is for hot duty cycle calibration,  it in fact puts ISC electric modulation into the center of its range.
the bleed screw should never be touched on any cold engine ever .







Good to hear that the effective screw is steel, further inside the throttle body.

Many thanks!

[fixkick]

order matters here, on 16v and 8v.
1: no vacuum leaks. or main induction leaks mAF to TB. air horn.
2: MAF must not be bad and many are now. for sure china clones new, 100% POS, pieces of Squat. those, get CARDON rebuilds.
3: IAC bad is common now, 2021. 20+ years old. vast things fail.
4: FPR dead. and fuel mixtures way to high. now like this.
5: ISC needs to be cleaned.
6: EGR bad stuck open or love to at ever stop sign. (landing )

unless all that is good the calibration steps can fail.
and PCM idle up pins at the wrong voltage , any, means those input things are failing like bad PS overload switch etc.
ECT bad, will cause richer running and then add vacuum leaks wow engine screams.

the 97 is obd2, ever do full scans?
see all DTCs
all pending DTC
the look at all sensors to be sure al read correctly for cold and hot engine
is hot RPM 800 not , scanned.
is water them 180?>
is MAF working right scanned
is engine in closed loop status , hot idle?
we check it all first before calibrating anything.

cases in point
TV must be closed fully and not molested
the do TPS calibration steps.
Bleed screw can not be calibrated until all illegal air leaks are cured. or just wasted effort.
if the bleed screw is CW max in out, closed, that means PO had hot idle failing hard and this was his nasty fix. (his bogus bandaid)
the ECU sets RPM HOT , not owner of cars and is by EPA laws infact this.
yes we do to Dutycycle calibration say ever 10 years, to adjust for natural changes in the engine, loser engines make more power for example.
keep in mind the engine even runs at 15,000 feet altitude. thin air , engine as less power so ISC opens more.
if the bleeds screw is set wrong the engine fail at low or high altitudes.Hot engines,
or super hot days, or more humid days, on humid days engine makes more power and ISC closes a tad
if the cars electric load goes to full Alternator current flow, 50amps. or 700watts or a bit over 1 HP taken off the engine crankshaft and ISC opens
or shifting from park to drive , ISC opens way more. for that load.
the ISC and PCM form a servo loop, closed loop servo. regulating RPM.

[Peter Wood]

order matters here, on 16v and 8v.
1: no vacuum leaks. or main induction leaks mAF to TB. air horn.
2: MAF must not be bad and many are now. for sure china clones new, 100% POS, pieces of Squat. those, get CARDON rebuilds.
3: IAC bad  is common now, 2021. 20+ years old. vast things fail.
4: FPR dead. and fuel mixtures way to high. now like this.
5: ISC needs to be cleaned.
6: EGR bad stuck open or love to at ever stop sign. (landing )

unless all  that is good the calibration steps can fail.
and PCM idle up pins at the wrong voltage , any, means those input things are failing like bad PS overload switch etc.
ECT bad, will cause richer running and then add vacuum leaks wow engine screams.

the 97 is obd2, ever do full scans?
see all DTCs
all pending DTC
the look at all sensors to be sure al read correctly for cold and hot engine
is hot RPM 800 not , scanned.
is water them 180?>
is MAF working right scanned
is engine in closed loop status , hot idle?
we check it all first before calibrating anything.

cases in point
TV must  be closed fully and not molested
the do TPS calibration steps.
Bleed screw can not be calibrated until all illegal air leaks are cured. or just  wasted effort.
if the bleed screw is CW max in out, closed, that means PO had hot idle failing hard and this was his nasty fix. (his bogus bandaid)
the ECU sets RPM HOT , not owner of cars and is by EPA laws infact this.
yes we do to Dutycycle calibration say ever 10 years,  to adjust for natural changes in the engine, loser engines make more power for example.
keep in mind the engine even runs at 15,000 feet altitude.  thin air , engine as less power so ISC opens more.
if the bleeds screw is set wrong the engine fail at low or high altitudes.Hot engines,
or super hot days, or more humid days, on humid days engine makes more power and ISC closes a tad
if the cars electric load goes to full Alternator current flow, 50amps. or 700watts or a bit over 1 HP taken off the engine crankshaft and ISC opens
or shifting from park to drive , ISC opens way more. for that load.
the ISC and PCM form a servo loop, closed loop servo. regulating RPM.


Helloo,

Thanks for all your advice.   Here's photo of the offending item, top of Throttle Body view, with the broken up plastic cap? in centre.
If it is just a cap, then I can dig what's left of it out and should find the real adjustment screw below?

[fixkick]

sorry so slow, that cap looks like broken plastic cap to me , just dig it out with ice pick or nail held in Pliers.
the screen is deeper the cap is just a dust cap.

[Peter Wood]

Good Moring,

Just thought I'd share my solution.

The auto-choke module, see above picture (thanks FixKick) was blocked with gunk and rust, as were the inlet and outlet water hoses.  If you look at Fixkicks video on induction hose routing on his 95 Sidekick, you'll see all those hoses, first leading into the IAC then on into the auto-choke module that's screwed into the base of the throttle body, then back into the base of the thermostat housing.  

All I had to do was clean out or replace all the hoses and auto-choke module, make sure the water flow does what it's supposed to and voila!  Fast idle drops down to normal idle as intended after the water heats up a bit.  Confirms the IAC is working as advertised.

I guess there's a couple of learning points, keep the coolant clean and inhibited at all times and don't use the gunk you can buy to stop radiator leaks because it'll probably block those small water hoses.

Good luck everyone!