1990 tracker isc solenoid test?

[fixkick]

take the air horn (top of TB) off turn it upside down and see what is there, not same on 98/90 gen 1 has no air bleed valve device.

[fixkick]

The ISC on the 89/90 is not documented at all for sure inside, only our 91+ up is fully documented, and 100% dismantled and photos.
nobody ever did a 89/90 I have ever seen. but the valve most close 99% or more, and not leak air. with no wires connected to it.
it is just an air valve, (solenoid operated) with no power the valve is closed for sure just like 91"+
but do know that the valve, this old does leak air , ALL do that old it has rubber seat inside if you saw it it would look like moon craters.
but can be re adjusted, just as the photos I posted imply, same as 91+ only hidden
here it is again
https://fixkick.com/IDLE-AIR/1989-90/ISC...index.html

see that? see frame 5 ,see Re-adjusted? and calibration screw.
we adjust them when this old and leak turning the screw so the leak just no longer leaks or just tiny bit, do not over tighten this screw.
that helps the 91 year too, but is 5mm hex screw or 91+
the valve most close fully or nearly so, most this old will not seal 100% or is that necessary, just mostly. see?

[fixkick]

we do NOT have this photo on any Gen1 ISC

this is my work to teach who it works, yours has no water heater hose.  oops i thing my spring is wrong, for sure it holds the valve closed.
see the rubber seat ring there, that wears?
what is inside yours, I have no clue, but does close and is a valve. same.  note body is missing below just the guts.
springs can rust to nothing inside and now is ISC useless. it must close under spring pressure and seal , mostly not 100% just lightly closes, and lands.
many of these fail and make huge racket on 89/90 only.  very load noise. and are death throws.

[rjm]

Once I find a new isc I’ll dissect the old 1 and take pics. It clearly a simple valve just not clear what is path of flow - 3 holes in valve and 3 holes in TB. With 1 of those being the polygon shape blocked by gasket.
If I shake the old one it does rattle a bit. But the fact that all 3 holes pass air to one another with no power I’m betting this unit is dead and allowing too much air / lean condition.
We will see - soon

[fixkick]

Once I find a new isc I’ll dissect the old 1 and take pics. It clearly a simple valve just not clear what is path of flow - 3 holes in valve and 3 holes in TB. With 1 of those being the polygon shape blocked by gasket.
If I shake the old one it does rattle a bit. But the fact that all 3 holes pass air to one another with no power I’m betting this unit is dead and allowing too much air / lean condition.
We will see - soon

it will not go lean, that valve stuck open is all metered (MAF)  air.  (if that gasket leaked that is unmetered air and yes lean)
it only makes the engine race too fast at idle.

but yes, seems it is struck open or the spring inside rusted to dust.
lots of humid are ran through this for 25 years.
rust happen, there. can be.
good luck with this job, hope you can find parts.easy.
cheers !

[rjm]

once taking a look and reading your replies I understand the gasket covering the polygon shaped hole is no concern. I uploaded a few more pics with notes with the hopes others will find them useful - along with your pics and details.

[fixkick]

once taking a look and reading your replies I understand the gasket covering the polygon shaped hole is no concern. I uploaded a few more pics with notes with the hopes others will find them useful - along with your pics and details.

you can see the new gasket  photos show no cut out, as seen below at "X" (on any year)
the round small hole is open "S" below.
the poly hole is not cut out in the gasket.
as you can see there are 3 holes in the ISC
and in the TB air horn , at least 1 hole , in the ISC sucks fresh air from the air horn. (from air cleaner path.)
the other ISC hole(s), sends this idle air down to  the bottom hole of the TB and this is hot idle air. this one hole in to intake man. plenum box.

the other air hole is the (thermal)IAC, the IAc SUCK AIR FROM A SIDE slot (rectangle) in the  area of the air horn TB juncture. seem below. IAC suck port.


here is the 91, 
it has different things here, so lets try to correct those, I have no photo of your top air horn underside like seen here on 91.+
the IAC suck port is the same , the  99% rule here is not true on any 89/90. at all. ignore that 99 rule.

the gasket at X, is there on all 8valve engine, as see below.
The So called "S" port is what varies. the S port mixes, IAC air and mixes bleed air in the 91.  on the 89/90 there is no bleed port at all nor its screw valve.
I am sure the gasket is same on all 89-96 TB. 
The only big difference is the lack of bleed and the internal mixing of IAC and ISC outputs,deep inside.
the TV valve on 89/90 years only serves as the BLEED path , the 91+ this bleed update makes idle duty cycle adjustments way more easy. (unlike Gen1)


Thanks for sharing !!!!!!!!!!!!!
yours is here found it. the air horn, I can  not see the upper side of this photo, what is the boss there? (top , left side of air horn TB) as seen here.?
that is  a bleed screw valve on 91. why is that here? that BOSS !? I think this only distracts me.. now.
I can now see clearly that 3 holes to ISC 90" and the atmospheric side are the 2 outside holes, the small hole is vacuum side suck hole from phenum
now we know the extra hole is for fresh air side and look again the cut out notches in 2 extra holes (outside suck vacuum hole)
see those notches, that for sure bypass any gasket actions on this side? sure does. the enter hole is round not the bottom.
The bottom hole  poly hole is blocked,  on all years.  I Revised your photo here.  F = fresh air,, Vac is plenum suck vacuum side.
The results of not having the X gasket blocked with normal gasket I do not know, id have to XRay the lower TB to answer that. but is in fact blocked on ALL.


91+ only. below.showing the exact spot of the new idle bleed screw. just to left of FPR port.



SOLVED !

[fixkick]

the 3 tests I do on all 8V for idle problems, vacuum hoses all good and things on the end of them not leaking air.
I block the IAC port on a hot engine to prove it does not suck air hot, if that test fails the IAC is TOAST, (wax pellet inside is DEAD or weak)
there are only 2 ways to block IAC, clay in its suck port up top or the 3 screw cover off and pack clay in there. or a TB base gasket that blocks IAC/ISC air port.
obviously the blocking TB BASE , port, only shows ISC or IAC is bad, or not. and not which one is it fails this test.

the other test is is only for ISC
those 2 tests are , 1: find a way to cut the ISC wire, or pull it pin out of the connector (either of the 2 pins to ISC) kills dead the ISC and is now blocked.
ISC having no PWM 200Hz signals from the ECU goes fully hard closed valve on a normal engine this test causes.
a: engine stall or drops 400 RPM or this act show ISC is mostly working.
b; does nothing the ISC may be leaking. , motivating me to do test 3:
3: This test is to make a new ISC gasket that blocks all 3 ISC ports, this defeats the ISC, 100% and rpm most fall hard, to 400 or stall, if not your air leaks are not in the TB or the TV valve is set way too far open,

on this year car the TV is the idle duty cycle calibration point, so we unscrew it to get 800rpm then turn just a tad more that screw for better regulation;'
or do the duty cycle calib now. (correctly)
in all this checking the DASH pot is retracted, not touching screw with same name seen above. yellow arrow.

the testing for too high idle is all about blocking all possible air paths.

[fixkick]

the only tricky part for  me (on topic of  bad idle, way too high)

is those pesky 3 screws on front end of IAC,

that will not unscrew, and fear of breaking them off.

that is why Id clay  block the top IAC fresh suck side of the IAC to prove IAC is not leaking air. hot.

this hold true on all 8v , any year.
if the screws are stuck "at Triad"
the only way to test this thing (IAC) is to clay block-up the fresh suck side up top. marked 'input ' here.  or the hot water test in pan of water. hot.
I use std, drill bit shanks , 1 to 60 drills set to use them as round feeler gauges.  40f is .040" gap, TB in refrig next to MILK Jug. see?
150f is hot pan of water submerged.
and  -10f is my freezer next to prime rib. LOL
the ring does spin (threads) and I think has glue on it , to lock in the factory calibration, im sure on flow bench in the factory.

[fixkick]

once taking a look and reading your replies I understand the gasket covering the polygon shaped hole is no concern. I uploaded a few more pics with notes with the hopes others will find them useful - along with your pics and details.

they will, the car is rare for Gen1. super rare. how many 90 cars are on the road today, we see none down here. at all.
when I do see one, i run over gander at it , like a kid and go GOB smacked. , wow. (face palm)
My wife then looks at me, and goes, "it's just like your old GEO Cracker" that is her words.

one again thanks for sharing any 90s photos for sure engine bay, with the gen1 TB, ....

one guy here had freeze damage in side the IAC, and not easy to find or prove, with out lots of hard work.
anything can be possible, for sure ice damage. 31deg F is worst, just as it freezes, bam. huge damage.