Cold idle when hot?

[Deadduck]

I have just finished doing a full rebuild on my g16b started it runs and drives fine timing ect all good when warm it was idling at 800-850rpm as normal but after about 30min of driving I stopped to change into 4wheel drive and the idle was at a constant 1500rpm where it normally sits when fully cold after turning off letting it rest for 30min and starting again still the same would this be the Engine Coolant Temp ECU Sensor or is there something else that would cause that?
Thanks

[fixkick]

94 Vitara not in USA>
and is 5speed
and is 80c.
but what is the drive line, stick or auto(3/4speed)
4wd?
can i have photo of engine so i dont need to decode your market code? (i can but, photos are magic as is a chassis tag , photo)
some markets run CARBs. up to 2001 and beyond. so.....

some G16 (ave 5 class types of engine and fueling)
tell me it 16valves,,,,,
got a tag like this, if yes, what is your 24?(market code)
the above line tells what engine it is and drive line. that i can decode easy.

would like photo of engine
as there are many parts that vary
egr, intake man. throttle body types and 3 carbs.
ive unique motor driven ISC, more that 2 wires)

[Deadduck]

It is a 94 vitara 5 speed manual yes hot 80°C sits there perfectly (have aftermarket gauge) all throttle cable set correctly all happened on same drive was working fine now not working fine no cel on I will check the ect when I drive it next

[fixkick]

HOT idle failure...s
rpm wrong. hot. lots..... (less if i can SEE THAT ENGINE !)
engine not at 180F or more. 82C up.
throttle cables set wrong. up to 3 cables. must be set loose.
ECU in limphome , mode, and when so,,, cancels all idle controls now. scan it or get the flash codes.
ECU idle up pins true, (a.c on, p/s overload) and more.
on 8v engines, (ONLY) aNY AIR LEAKS,, ON 16V AIR leaks cause lean and RPM DROP, so... id love a photo of your engine..... sure would........???????
ECT reads wrong, if it read like 150F? , 1500 rpm is normal as that is cold idle speeds, dictated by THIS VALVE.
hot water not flowing trough the IAC (location not same on 8v as 16v but work the same way)
air leaks on 8v give full engine power
air leaks on 16v goes lean, and low engine power, and RPM.
so..... what engine is there, i need a photo outside usa, as inside USA it has only one 16v MPI engine. just one, but other countries, 2 engines, and 3 or more fueling systems.
more... sure, isc leaking air.
more, iac leaking air at 180F, (82C)
if rpm is 1000, then ECU is in idle up mode
there is no hot 1500 modes, ever.

does the engine flash code 12 on demand?
the DLC jumper clip?
test?
this is first and most easy.
ignore comments on NAG lamp features. it's a USA EPA bs feature.
http://www.fixkick.com/CEL/CEL.html#OBD1codes

[Deadduck]

That's the best pic I got ATM of it it is mpi 16 valve

[Deadduck]

I used it today and rpm was still high when i got to work how ever I went out for lunch and i stopped and it was back to normal and is now acting all normal when i drive it. so not to sure any more

[fixkick]

that engine can NOT run, with like 10things missing. must be very very old photo...
what if the current photos , i saw something wrong.???
and i need your blue chassis tag , codes. on fire wall , or what country car was bought new, or present now?
i see your DLC connector on the left why not jumper the 2 pins and see the DTC errors? why not use the jumper wire and see if you have errors first?

i shrunk the photo to fit, THIS TIME CURRENT



ok it is a 16v, with MAF, and MPI EFI injected.
and is at 80C (tad low but gauges always lie, a bit)
but is above IAC closure point.

my 97 did this.
i grabbed the throttle body throttle bell crank (see cable, no cruise no , a/t) and turned it very hard by hand , if it closed more the butterfly TV valve is gunked up.
if it dont turn and is bottomed out, then the TV dont leak.
easy no?
there are only 4 air paths for idle,
1 TV, (is 100%closed)
2 bleed screw path on top under a cap
3 the ISC (electric powered ) unplug the conn, what is RPM now, when rpm was 1500, ????????
4 and IAC, thermal. if the 2 water hoses are clogged or in the valve, it will stick open and idle races. this air valve is always closed hot , (mine was not and had to replace it)

rule 1, the engine can not run with zero air. a fact.
this one fact makes diagnose simple (in theory ) but not in practice due to the many paths that can leak, and if there are 2 or 3 more failures, as most seem to have this old.


here is what you have, off my bad idle pages,,, (extensive info)
http://www.fixkick.com/IDLE-AIR/fastfix.html

this is all there is to normal air. see my red arrows here and letters?

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first things first.
go to the DLC, diag, link conn.
insert the paper clip, best is with engine running, (inserted keyon, is old errors, then start and new errors flash out)

the steps are here, its like 5min work.
http://www.fixkick.com/CEL/CEL.html#OBD1codes

we do that to be sure the ECU is working, and not in limphome or worse backup mode.
its always step one any time the engine runs bad, on all cars, made with EFI and even 2016 cars.
step 1.
is the ECU unhappy, we are its slave.... for sure.

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many times, the IAC has the 2 water hoses packed in crap.
input hose,
output hose
or the valve itself is packed, in junk, gunk,etc. so the valve never gets 80c full flow of water.
if that happens the thermal device inside, sets in the cold position and valve is now stuck open hot.
lucky for me , i have $15 IR, pyro thermal gun, i point the laser at the isc base and see, OMG, its 130f./ 54c that be dead wrong, water path is blocked.
super easy to do with tools... no?
btw IAC closes 100% at about 150F. or 65C

ever seen this?
http://www.fixkick.com/IDLE-AIR/Slide_Sh...ge_25.html
gunk can in fact block open the TV.
and will leak air, and race and be intermittent too....

im not guessing here, just showing some common examples.
i dont test, I test. i do the simple tests and proves whats wrong.

what is rpm with ISC unplugged, electrically, (the connectors on VIT are all locked, and buying a new one is near impossible..) so go easy.

here is the IAC

see my slide show and ignore 8v parts. only 16v parts look,

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more sure
the idle switch must be closed at idle, 0v on idle switch pin
if not idle regulation will be dead, and idle random..
my TPS page covers this.

this switch is part of , the TPS.

if the TPS idle fails, the ECU tells you this fact.
but that is step one , the DLC jumper, mention above first.

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what country?
or if car bought in other country, where?
each country runs different ECU and some other parts.
some Vit have no , CAT< no EGR< and no 02 sensors.
see?

i see you exhaust is not stock
does car still have an oxy (lambda) sensor on end of exhaust header?
does car still have a CAT.?
are there any other things missing? the photos shows vast things missing, why?

[Deadduck]

Old photo yes here is a new photo yes still have o2 sensor cat cut out egr blocked with headers market code is 24 all pipes and coolent gallires are all clean done a full rebuild cel is code 12 which is normal now seams to be intermittent

[fixkick]

good code 12 (happy ecu) its not in limphome, nor backup mode, good.
i see no missing major parts., all look stock
no idea at all what that silver object above and rear of Valve cover.?
sure market 24 is Australia.

so test one (TEST 1)
when at 1500
open hood and see TB see throttle top in photo push firmly the crank to your left, this closes the throttle 100 % if it has gunk inside.
then if that does not lower idle (agood sign), we then...
1500 rpm still.... hot idle wrong.

TEST #2:
un plug the isc connector. engine will stall or run super slow rpm 400 or less.
if not you have a leak,
(on a hot engine here are only 2 air paths, isc and bleed) no others, with isc closed, only the bleed path is open, (if at all) and engine stalls.
one exception is some 'BAD GUY" unscrewed the bleed screw 10 turns, to fully open.'
this screw is idle duty cycle setting and not idle speed. (ECU controls speed only)
when you see 1500 rpm that means the ECU lost control of idle, a fact.

just 2 tests, and we can reduce the list of possible greatly.
CAN YOU DO THOSE?
JUST 2 TESTS.?

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I SHRUNK your photo again,.

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TO FIND FAST IDLE, TESTs MUST BE DONE.
guessing is hopeless ,
on a good 16v, there are only 2 air source hot, this is a fact. (BUT NOT YOUR CAR)

if test 1 passes
and test 2 fails, I'm sure it will
but if test 2 fails, we then do test 3

TEST 3 is.
PINCH TEST is #3
pinch the ISC air line (2 are hot water) 1 is air, pinch air hose. (keep isc unplugged)

if RPM falls to 400 now or stalls, that means the ISC is bad.. (stuck open , clean it) test it. its leaking air way BAD.
if RPM screams pinched, this means the IAC is stuck open. (if lucky and not H3LL mode and end of this page)
see this logic path >? note how i make zero assumptions, as most of them are dead ends. wits ends.

id say engine i ok. if it has full power, ill guess yes its ok.

test 4: is next,

the IAC test. (we first make sure it fully hot, some way, or prove the water tubes to it are not blocked, end to end ever inch free flowing water)
IAC is 100% a thermal acting device.
the IAC has 2 hoses. both can block, end to end, even the source to said hose can block, we back flush all these parts. to test them for flow.
The IAC itself can water path clog, and make it fail.
the ISC has a water path if blocked can block water to the IAC, because they are in SERIES.
see on my annotated drawing here.
http://www.fixkick.com/Cooling-engine/16...aths2w.JPG

those are all pretty simple tests, so far almost no tools. but owning and IR pyro gun saves huge labor. for sure testing radiator cores.>>....

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(point and shoot, ah 170f t0 195f here)
bad guy #2, failure seems like every day we get this guy. (who are these persons....,? )

my page
called screwed again, covers this lil' horror , someone played with the TV stop screw.... again...
http://www.fixkick.com/IDLE-AIR/screwed-again.html

btw the bleed duty screw is here. (fiy here it is)
http://www.fixkick.com/IDLE-AIR/16V-Tbody1w.jpg

back to screwed again...
The TV has and idle stop screw that must never be touched. (same with ISC calibration screw)
if found molested, ( many unknowing mechanics, turn it to raise idle speed, (like carbs of old) but is bad news that. all bad news.
The fix, covered on my page on topic. is. (this does work)
i set them to 0.0005" gap, or 0.0127 (.0130mm) using feeler that size, note the leading zero there, in front of 1. NO TYPO.
this gap is about size of mums, kitchen aluminum foil , cheap box size, super thin )<<< poor mans feeler gauge it is.

the ECU can not deal with huge errors, or added (stacked) up.
bleed screw fiddled open. (this is ok to play with)
TV gunked up, blocking proper snappy closures......
TV stop screw, hell. done by Mr. bad guy..... simple fix.
ISC leaking, clean it, test it with 12vdc battery, 12v=open ,0v = closed, its spring that closes it, and mag, field opens it.
IAC leaking , (i have a test, ask) (i use a clay tests) removing the 16v IAC can be near impossible, i dont try, i test it with TB as ONE !
ISC water path blocked.


what is happening when you see 1500 on the clock hot. parked.
1: ECU has lost control of idle, is a fact.
2: why we don't know, yet, only tests prove why.
3: personally i pinch the ISC hose, like wild man,. bam, pinched. (rpm drops, only a tad,? or , rpm to 400 stalls) ???????????
if rpm falls super low and or stalls, then ISC is stuck open., (so much is learned here in 5min work , no?)
if rpm only drops a bit, say 1500 to 1000>? then you have IAC stuck open or TV stop screw molestation, or bleed was unscrewed 10 turns.
i screw in the bleed, and rpm drops a tad. oops, we do have some leaks for sure.
Keep in mind, I have no idea from where. Im only checking legal paths there, the 4 legal paths.


now the bad news. what i call H3LL MODE:
on some engine,(seems common on old engines) there are 2 problems. that in a sick sick fate of bad luck , help each other. and that is what?
Not saying this is it.

1: engine in limphome or fuel pressure at 60 PSI (FPR fails hard, on all these old cars , many now)
and it's super rich running, ECU can NOT control fuel mix right, now..... ECU can not know fuel pressure is 2x normal, its just LOST.
then
you get and illegal vacuum leak, this illegal , unmetered air supply ADDS to the illegal fuel flowing and engine races.
this is A DUAL failure. and does happen.
so keep and open mind, and is why i check the easy stuff first.


keep in mine good 16v go lean , with vacuum leaks.
and run slower. not faster
but in H3LL mode, the opposite is true.
on a good engine you can create a vacuum leak (small) and ecu corrects the mix, using closed loop.,
if you add more vacuum leaks the ecu looses control and slows, RPM.
on rich engine, the opposite happens.

[Deadduck]

I haven't been able to test it yet as it has come right idling normally 1500 rpm cold and 850 hot that silver thing is my starter bypass solenoid as I have gone through many solenoids on starter