90 tracker distributor vacuum advance bad idling issues

[Banned]

Hi all. I have a 1990 Geo Tracker 4x4 5sp ac convertible 197,000 miles. Am experiencing bad idling issues, for the past 3 months, MPG at 17 and rpm's at 2000 - 1500 and then surges adn drops between 1700 rpm and 1000 rpms. Going one by one found a bad IAT, missing gasket (3 screw one) for the air valve (wax thing) bad spark wires which I replaced today with some Bosch, replaced dizzy cap and rotor (china) w good quality and seems to be improving but since I was at the dizzy, I checked the vacuum advance mechanism with a vacuum tester and could not get the advance to HOLD any vacuum. Could not even get it to hold the 400mm that FSM calls for. It bleeds in air back immediately. Question is should this unit be replaced or did I do something wrong testing it. Also, this bad MPG has been since I got the car 5 years ago and 10k miles later. Replaced fuel tank, muffler system and have never gotten over 23 MPG hiway miles with the wind behind me. Compression reads when hot 1=170 2=172 3=178 4=187
#2 spark plug was dark and not beige like the rest but probably due to the bad wires. Also, this bad idling used to come around once in a while and then it would be fine, but like I said hte last 3 months I hardly use the car and idles like a mongrel. THoughts please.

[fixkick]

welcome banned! lol (G16a, gas hog, burns fuel like Huge V8 Chevy Blazer)
17mpg , is horrible 28 normal. 24-28 range. (is air cleaner clean and fuel filter, completing the tuneup)

Surge is the ECU telling you it lost control of hot IDLE.
bad IAT is very rare, G16a (1990) is a one wire, Intake air temp. sensor, that ? ECT fails 10x more that that,becauses runs 10 times. hotter, but both are robust. unlike say 02 sensor.
3screw is the IAC, Idle air, controller , 100% thermal. and must close above 150f. gasket missing sucks air, and all vacuum leaks cause fast idle. (if over powers iSC)
The vacuum advance has a diaphragm and all must hold vacuum or they are cracked, this is a standard test on all such vacuum actuators. pump 8 inches, hg. and hold, if not its bad.
15 is peck 400mm-GH, but i use 8"HG (200mm-hg) as its more gentle on very old parts.
first test the tool, with hose. put finger or a screw on end and see that the tool holds a vacuum, many dont'. then test any diaphram, there is. for leakdown test, its called.
one also looks to see the vacuum advance plate moves and holds,
compression is very good for 27 year old engine, amazing really.

MPG, good takes this:
CEL lamp on key, out running. if not, get the codes, (diag jumper) if not out the ecu is in limphome (failsafe) and will suck fuel like mad.
1: engine good, seems ok, check.
2: engine coolant reaches and holds 180f or more. must hold. or ECU goes nuts. IAC nuts and ecu never leaves cold start mode, sucks gas like mad.
3: good spark seems it is now, but does it advance like the book shows, gunning throttle. vacuum and mechanical advance, (ECU only does fuel not spark)
4: fuel pressure at spec , 34.1 to 39.8 PSI. (high end at sea level, pressure is based only on altitude.) see test port at fuel filter ,6mm screw.
pressure holds, at idle or cruise or gunned throttle. (unlike G16b)
5:fuel injector leaks, (air horn off TB, key off see it drip?, at the moment of key off (2man test)?
6: 02 sensor stuck at 0v all the time, runs rich bad 02 or exhaust leaks near it.
7: using a timing light test vac, advance and mech. advance if say the mech is rusted and stuck it will burn way to much fuel... advance exceeds 30degrees (left of scale ) or more gunned to high rpm parked, in Neutral. and see it advance aggressively.


AIR , is complex.. (only to point that so many possible)
fast idle is air leaks (aka, vacuum leaks) and all leaks cause fast idle, (ISC lost control) all do natural leaks or unnatural leaks ,all do.
its not cause of 17mpg, its just one more problem, as all do this old. many problems.
ISC leaks (aka stuck open), IAC leaks (both natural and wrong) by natural i mean air that was filtered at the air filter. IAC leaks when coolant never reaches spec,180f.
Un natural leaks are gaskets bad, like you just found and vacuum hoses cracked sucking air, even the brake booster can fail and let air suck in, vacuum will find any leak fast and easy.
TB base gasket leaking, some times the ISC on the TB is bad and leaks, its got gaskets there that can fail. or was molested at its rear screw.(hidden)
fast idle can be Gunk holding the TV open.
one of 3 throttle cables , 2 on MT. not set with 10mm slack spec, throttle cable or the cruise cable (option)
idle calibration set wrong. (throttle stop) causes ISC to loose control of idle, the ISC does this, via ECU commands. the ISC has 20 rpm, 800 and 950? the latter is idle up mode.
on 90,idle up is A/c on, heater blower on, head lamps on, or defrost on (option for rear glass, i bet is missing or dead)
800 rpm is spec,at all accessories OFF. all .

finding a working iSC on any 89/90 is an amazing site, and takes hard work to cure if out of control , the ecu is programmed to 800 rpm in a servo closed loop
'if it can get 800 ,it hunts (illegal today, ask Toyota the cost of that billions. fines)
hunting is unsafe it should close the ISC and hold it closed, but does not, it hunts in the blind and wrong attempt to gain control, (evil on a/t boxes never m/t) on m/t driver is always in control.

end air.
high mpg , can be brakes dragging or drive line bad, (bad bearings in trans,/axles/wheel bearings, etc) which Ill assume all is ok. so above is just answering for engine issues.

[Banned]

Thanks so much for a very detailed answer and this is what I've done so far:

[Banned]

Thanks so much Fixkick for a very detailed answer and very much appreciate what you do for us,
this is what I've done since:

Replaced distributor w/remanufactured, for kicks applied vacuum 400mm and held.
Not able to do timing since idle's all over the place. The dizzy I replaced also had something loose inside, one of the
weights (springs) seemed to be loose, broken. Also the rotor spring back did not go back smoothly as does the new one.
After a few test drives the surge seems to be faster than before and after car warms up.

Yes the MAT (not IAT) was bad, had a big crack just like in the pictures you have on your site, vacuum is a pretty and mighty powerful force, no? and these are the chracteristics I recorded
in hot water: 70° = 2.34 Ω
104° = 1.63 Ω
140° = .77 Ω
176° = .38 Ω
212° = .21 Ω
ohms spiked severely at least once as water temperature rose between 140 and 176
MAT was replaced, also seemed to not have been tightened by previous bad guy and had a steel corroded washer that did not fit very well on center.

Today I was in hot water again as I've had suspicion of the ECT sensor or possibly the bad guy that installed the thermostat did not do it right:
ECT sensor test
Key on/motor off
Result: Voltage 4.71v Visually: ok
Characteristics:
Laser digital Thermometer
32° = 5.89 Ω
68° = 2.05 Ω
70° = 1.95 Ω
104° = 1.00 Ω
140° = .46 Ω
176° = .27 Ω

Analog Thermometer
32° = 5.88 Ω
65° = 2.66 Ω
104° = 1.36 Ω
140° = .59 Ω
176° = .35 Ω

Also today: Checked thermostat for proper installation, position and visual inspection.
Result: hot water test begins to open at 178°, full open at 180° degrees, weep hole to front and visually looks like a new part.
Also replaced wires with Bosch, nice fitting, the previous had corrosion even though they were replaced a few years ago, yeah some off brand junk, dizzy cap and rotor also new with good quality type.
CEL never goes on except when ignition on/motor off.
CODES: 12, 12, 12... all day and all night long for the last 5 years I've owned it. Never throws anything else even though it idles like a mongrel from hell.
ISC at 6.6 ohms and sealed nicely. ISC is only a few years old.
PCV test. at idle, placing finger over nipple, ticks and sucks replaced a few years ago..
Cleaned vacuum nipple at manifold for dashpot vsv vacuum supply and replaced vacuum hose
(nipple to vsv)
Re-grounded fuel pump ground at L tail lamp. Oiled fuel pump terminals at rear lamp housing and ground.
Checked engine grounds and ECM ground for positive contact.

Will test for fuel pressure and injector drip next after I reinstall the coolant thermostat and ECT sensor.
I tried the timing light on the injector with motor idling but could not see any fuel spray pattern...
also will try timing the darn thing if I can get it to idle at 800 for a few seconds which it does after warming car up and turning it off for about 10 minutes, it idles nicely but then it starts gaining speed until it reaches 2000 and then it starts its surging.

[fixkick]

lots of progress ! and the double failed, distributor, wow. great work there.

Thanks so much Fixkick for a very detailed answer and very much appreciate what you do for us,
this is what I've done since:

Replaced distributor w/re-manufactured, for kicks applied vacuum 400mm and held.
Not able to do timing since idle's all over the place. The dizzy I replaced also had something loose inside, one of the
weights (springs) seemed to be loose, broken. Also the rotor spring back did not go back smoothly as does the new one.
After a few test drives the surge seems to be faster than before and after car warms up.

I SUSPECT YOU HAVE THE DECIMIAL POINT WRONG IN EACH OF THE BELOW.
THE METER I GUESS, IS AN AUTORANGER AND WITH LCD DISPLAY AND ON OHMS THERE IS "K" SYMBOL YOU MISSED SEEING? JUST LIKE CARS TACHOMETER.

Yes the MAT (not IAT) was bad, had a big crack just like in the pictures you have on your site, vacuum is a pretty and mighty powerful force, no? and these are the characteristics I recorded. ,,MAT IS OLD NAME AND IS OK TO USE.
(DECIMAL POINTS WRONG) BUT I CORRECTED 176 FOR YOUR, THIS IS IAT, INTAKE AIR TEMP IN PAN OF HOT WATER IT'S WINNER.

in PAN OF hot water:F 70° = 2.34 Ω
104° = 1.63 Ω
140° = .77 Ω
176° = .38 Ω (380 OHMS IS CORRECT NEVER, .38) (LCD SHOWS .38k = 380 OHMS)
212° = .21 Ω
ohms spiked severely at least once as water temperature rose between 140 and 176
MAT was replaced, also seemed to not have been tightened by previous bad guy and had a steel corroded washer that did not fit very well on center.
BOTH SENSORS NORMALLY READ THE SAME, THE IAT (MAT OLD NAME) READS SAME AS ECT. ONLY THE AIR SENSOR , IAT IS FASTER, (LESS MASS)
http://www.fixkick.com/sensors/ECT/my-plot-ect.JPG

http://www.fixkick.com/ECU/temp-sensors.html
Today I was in hot water PAN again as I've had suspicion of the ECT sensor or possibly the bad guy that installed the thermostat did not do it right:
ECT sensor test
Key on/motor off
Result: Voltage 4.71v Visually: ok
Characteristics:
Laser digital Thermometer
32° = 5.89 Ω 589 OHMS IS CORRECT NUMBER, DECIMAL POINT IS WRONG . mine reads exactly same
68° = 2.05 Ω
70° = 1.95 Ω
104° = 1.00 Ω
140° = .46 Ω
176° = .27 Ω VERY NORMAL 270 OHMS, 300 IS PAR.
THE DATA SHEETS ARE HERE FROM SUZUKI AND GEO.
AND MINE.
http://www.fixkick.com/ECU/temp-sensors.html
KEEP IN MIND THE SENSORS ARE NOT PRECISION, AT ALL, -+10 or +-20% accuracy, says suzuki or GM depends on year what they said.

Analog Thermometer
32° = 5.88 Ω
65° = 2.66 Ω
104° = 1.36 Ω
140° = .59 Ω
176° = .35 Ω 350ohms , the DP is wrong, sorry.

Also today: Checked thermostat for proper installation, position and visual inspection.
Result: hot water test begins to open at 178°, full open at 180° degrees, weep hole to front and visually looks like a new part.
Also replaced wires with Bosch, nice fitting, the previous had corrosion even though they were replaced a few years ago, yeah some off brand junk, dizzy cap and rotor also new with good quality type.
CEL never goes on except when ignition on/motor off.
CODES: 12, 12, 12... all day and all night long for the last 5 years I've owned it. Never throws anything else even though it idles like a mongrel from hell.
CODE 12 ONLY ,MEANS (SENSORS DIDNT FALL OFF, OR SHORT OR OPEN) CODE 12, IS GOOD, BUT TELLS LITTLE. BUT GOOD TO KNOW.

ISC at 6.6 ohms and sealed nicely. ISC is only a few years old. (GOOD , I DIDNT KNOW THAT, GOOD )
PCV test. at idle, placing finger over nipple, ticks and sucks replaced a few years ago..
Cleaned vacuum nipple at manifold for dashpot vsv vacuum supply and replaced vacuum hose
(nipple to vsv)
Re-grounded fuel pump ground at L tail lamp. Oiled fuel pump terminals at rear lamp housing and ground.
Checked engine grounds and ECM ground for positive contact.

Will test for fuel pressure and injector drip next after I reinstall the coolant thermostat and ECT sensor.
I tried the timing light on the injector with motor idling but could not see any fuel spray pattern...
also will try timing the darn thing if I can get it to idle at 800 for a few seconds which it does after warming car up and turning it off for about 10 minutes, it idles nicely but then it starts gaining speed until it reaches 2000 and then it starts its surging.

LIVE TESTS:
THe ect read live 0.65vdc hot 180f engine (across its pins ,running, black probed) or
stall engine, key on , pull ECT plug, measure ECT pins, 300 ohms (or on LCD meters .3K means same thing)

OK YOU GET A BETTER STATIC TIMING BUY CRANKING WITH FUEL PUMP RELAY PULLED. (KILL FUEL)
THIS PREVENTS IT FROM STARTING AND YOU CAN BALL PARK THE DISTRIBUTOR NEAR SAY 10DEG BEFORE TDC. (what ever spec is)

And you are correct getting timing exact (spark) takes a hot engine and 800 rpm, regulated.


what is next well the idle switch, on this car its a horror to set,
on this year the crazy TBI is devoid of the AIR bleed screw.
so one must do 2 things at once, not easy.

the one fiddles the idle stop for 800 rpm, and then adjust the TPS for[b] 50 to 300 ohms[/b]. on the idle switch pins, (its a carbon switch thus the odd readings) 50 to 300 is the sweet spot (my data)

the details are here. the goal is to get 0v on the idle switch at HOT idle, this is first or there will be no idle regulation;
link : (my page just for this 89/90 TBI engine) has factory data there too.

http://www.fixkick.com/All-Pdfs/M89/TPS/...ation.html


2000 RPM hot, (and that hellatious. suzuki illegal hunting,)

here is what id do if saw that. (first make sure idle switch reads ,0.0vdc, at hot idle, it must, if not fix that now, TPS cal)

1: is the DP retraced, I look next at end of DP shaft there must be and air gap at the end of the dash pot shaft, (PD end to bell crank stop) 1
OK DP is working , retracted 100% and passes vacuum leak down tests. as does distrib now.

2: I'd grab the throttle bell crank in the end of the TBI shift (cable bell crank) (if it moves there is something blocking it)
I now force the throttle by hand at the TB shaft and force it closed hard, man handle it. idle ok now? NO.
3: I then turn the idle stop CCW (counter clock wise) out, and see RPM drop, oops, it does, and magically when i get ear 900? the ECU takes over
and with ISC drops idle to 800 and it now regulates.at 800 now.
4: Ok its till screams. RPM. so i pinch all hoses, to finder the leaker,
one trick is unplug ISC, wires, (difficult) rpm must drop to 400 or even stall , if not there is a huge leak of air.
AKA: vacuum leaks, MOST vacuum leaks do 4 things, HIGH RPM, and surging and no 800 regulation
The iSc can in fact hide small leaks, but if excessive , it goes out of control as yours does
and all old suzuki hunt idle, (illegal today) it trying to find 800 and can't, it closes the ISC and 800 can not be reached so the silly thing hunts.
on newer cars, its shuts the ISC fully , no hunts allowed, and then sets DTC errors. for idle out of control but not back in 1989 to 1999

my answers wildl drift off to other vectors, as , for other causes depending on what you find above.
for example all small vacuum hoses do not leak
we check brake booster for leaks.
or check TBI base gaskets for leaks. (it has water path too)

I can be as simple as previous owner played with the stop screws. (there are 3) TB stop screw, DP stop screw, TPS calibration screws)
the 4th is ISC screws are hidden, and is new.

one trick on 80/90 is to add a switch on the ISC wire.
open switch, see 400 rpm, if not huge leaks, (400 is not a spec, its ball park , one way to say this , is idle 800 drop about 1/2)
this trick kills the ISC dead, (hARMLESSLY)


LINKS
tps cal 89.

http://www.fixkick.com/sensors/tests/TPS...only-calib.

spark timing 89 with factory pages,.
http://www.fixkick.com/IGN_timing/89-timing.html

[Banned]

April 26, 2017
TPS calibrated.
TPS Test Results:
CD idle = 0 ohms
CD full open = infinity
AD idle = 5.5k
BD idle = 0.5k
BD Full Open = 5.5k
Did not do live test can't find probes that don't damage wires. Where did you get yours Fixkick?
TPS seemed to have been fully clockwise, possibly P.O.?

Timing set 8° @ 800 RPM hot. Vacuum advance now operating.
Pointed laser thermometer at thermostat housing when hot = 180° - 200°

TBI throat is very clean and moves freely, nothing blocking it.

Brake Booster did 300mm and held, however I could not make it go higher since my hose hook-ups are crude.
Should I re-test or the above number or good enough?

O2 sensor was replaced about 5 years ago, but, in the mean time I ran the car with a bad cat. for 4 years, last year I replaced complete exhaust system (manifold back) including the cat. Did the no cat kill the o2 sensor and now the o2 sensor is getting even with the cat? (my apologies for the bad humor)

This morning test drove it and started out at 1600 rpm and slowly climbed to 2100 rpm and then the surging began, 2100 to 1600 to 2100 to 1600 and so on. Should point out that the previous years when it did surge was about 40° humid and especially after running on the expressway but only did it a few times, this time since December of last year it hasn't stopped except when it gets over 70° then it behaves somewhat.
When it ran "right" it went through start up motions well, 2300 rpm after 7 seconds down to 1900 and slowly to 800rpm after a few miles. Lights raised the rpm by 100 or so, ps raised it another 100 or so and ac raised it up 400 rpms. I do have to set idle after winter and after summer by about 100 rpms if that kind of info helps.
I live in Chicago but hardly drive it in the winter or at least when there's no salt on the ground.

[fixkick]

April 26, 2017
TPS calibrated.
TPS Test Results:
CD idle = 0 ohms
CD full open = infinity
AD idle = 5.5k
BD idle = 0.5k
BD Full Open = 5.5k
looks ok, there,
the TPS calibration on any 89/90 USA with the NO WATER ISC actuator is very difficult the suzuki pages are on my site covering this
the reasons its hard, no bleed screw, so you have to adjust idle to 800 then set tps calib (with feeler gage) the set idle then the feeler gap over and over until its right, a ROYAL PAIN!
the main page is here
http://www.fixkick.com/sensors/tests/TPS-testing.html
the page from suzuki is here
http://www.fixkick.com/All-Pdfs/M89/TPS/...ation.html




Did not do live test can't find probes that don't damage wires. Where did you get yours Fixkick?

This is called back probing, one can use, 10cent leather sewing needles in a jam or buy them from Pomona, co. or
https://www.youtube.com/watch?v=AizTcrU5Egk

http://www.fixkick.com/INJECTORS/NOID101.html#probe

with a set of alligator clips needles work.
you buy full meter probe kits with needles all ready there, at all time lead makers, like Pomona makes.. (oldest co. in calif that i buy from for 50 years)



TPS seemed to have been fully clockwise, possibly P.O.? (thats wrong)
if tps set wrong ,the car will hesitated at tip-in throttle. or idle speed regulation is dead.

Timing set 8° @ 800 RPM hot. Vacuum advance now operating.
Pointed laser thermometer at thermostat housing when hot = 180° - 200°
GOOD

TBI throat is very clean and moves freely, nothing blocking it.

Brake Booster did 300mm and held, however I could not make it go higher since my hose hook-ups are crude.
Should I re-test or the above number or good enough?

O2 sensor was replaced about 5 years ago, but, in the mean time I ran the car with a bad cat. for 4 years, last year I replaced complete exhaust system (manifold back) including the cat. Did the no cat kill the o2 sensor and now the o2 sensor is getting even with the cat? (my apologies for the bad humor)
love this humor, its great
the cat (if no smog tests) only needs to not be missing nor rodded out. it must have back pressure for EGR to work if EGR not needed then no cat needed.



This morning test drove it and started out at 1600 rpm and slowly climbed to 2100 rpm and then the surging began, 2100 to 1600 to 2100 to 1600 and so on. Should point out that the previous years when it did surge was about 40° humid and especially after running on the expressway but only did it a few times, this time since December of last year it hasn't stopped except when it gets over 70° then it behaves somewhat.


When it ran "right" it went through start up motions well, 2300 rpm after 7 seconds down to 1900 and slowly to 800rpm after a few miles. Lights raised the rpm by 100 or so, ps raised it another 100 or so and ac raisedt up 400 rpms. I did have to set idle after winter and after summer by about 100 rpms uf that kind of info helps.
I live in Chicago but hardly drive it in the winter or at least when there's no salt on the ground.

normal is 800 hot, and regulates there, its very accurate 800 the ECU actually counts crank turns, but can be 50 rpm off.
the dashpot fully retracts, so cold can be 2000 rpm or 1500 summer. (IAC rules)
at first start the Dash pot runs very fast RPM, then retracts in 3 to 7 seconds usually, longer in alaska.
the RPM is then dictated buy IAC util 150f water temp
when 150 or tad more is hit , ISC goes on line for 800 rpm.

that is how it works when working correctly
hot starts, 3 second Dash pot race then 800 now. all hot starts.


The ECu must see hot engine over 150f
the ECU must see idle switch closed.
all accessories off, or goes to race mode, 950? or 1000. no PS overloads. no AC or race mode is activated, (called idle up mode)
if those conditions are set idle is 800, rpm, near.
and will regulate. there,
if no regulation , then the ISC is bad or or you have vacuum leaKS.


YOU SAY SURGING,

SURGING MEANS ISC IS CONFUSED (or engine gross lean) there are only 2 causes. mostly.
WHEN DID THIS HAPPEN, FOOT ON THROTTLE OR OFF
IF ON , THEN THE TPS SWITICH IS FAILING.
WHEN YOU STEp on the throttle , the TPS idle switch goes to 5vdc.

the tps gap set is .086" and 0.094" on the automatic trans
so when you step on the throttle in .09" about the idle regulate ends at the speed of light (electron flow) and no surges possible after that .09" of foot motion. if it surge now the engine is grossly lean.

[Banned]

surging happens foot off and idling, never when I accelerate or maintain a steady speed, however on slow deceleration with my foot on, it tends to jerk - but not all the time.

[fixkick]

that is the ISC doing that, the ECU is cycling the ISC to find 800 and rpm and cant
my guess, is surging above 800 to why higher.? hotl.

id bet its not surging 700 to 1500, hot.
but is above 800 all the time, when surging
at idle. hot
that means you have air leaks, from somewhere, ever unscrew the throttle stop screw?
back side lower screw, the main stop.

what if PO messed with this?

800 is the target speed, hot.
the ecu on this old car is a tad nuts.
if it cant find 800 it hunts the ISC like mad.
(very illegal today to do that kind of software, on an automatic car , in drive, it is a run away car, (driver, daft, or kid or girl, panic)
IF STICK SHIFT CAR ITS NO BIG DEAL, (PAIN YES,BUT STICK drivers are always in control no big deal.. nor panic
but that is the ISC doing that, and the idle switch is closed, or idle controls be dead, and surging impossible, (isc surge)

[fixkick]

tell me more about the surge
RPM, hot when it happens. ?
good luck to you .