High idle, probably broken IAC, questions

[fixkick]

Hello,



Car Info:

- 1991 Vitara MT, 2 door, G16a, 4wd.

- 242000km / 150 000 miles

 - Plate in engine compartment.

  - TYPE: ETA01V

  - LAK625K17 (SWE, car has actually been sold in neighbor country FIN)

 - No AC




(Rear window defroster broken, cant test idle with that).

- Car runs fine, I think it has almost all horses still as it can get into 130-135 km/h (80-83 mph) on highway (yeah not fun to drive ).
- Fuel consumption is good for its age 29-30 MPG. Inspector said emissions are extremely good considering car's age.
- No CEL codes, no CEL light.

New stuff related to this and other stuff I guess:

O2 sensor, 190F stat, tb hoses, brake booster hoses and booster, radiator, radiator fan clutch, engine head gasket, water pump, camshaft belt, clutch and re-machined flywheel.




 Last summer we discussed about fixing high idle on another thread originally related to replacing blown brake booster. (Done).


( https://fixkick.com/forum/thread-vitara-...ent?page=2 )


After that I have done about every vacuum leak check and fix that can be done without pulling removing the TB. Due to COVID19 and restrictions car has been unused during winter. I have replaced all but 1 rubber hose that connects to the TB, its the short about 1" hose near engine. Could not change it with my fat fingers. So will change it when I remove TB, anyhow all hoses were still air tight after 30 years .



Anyhow situation is this.

welcome back.

DP definetlly works. After startup 3000-3500 rpm for 5-10 seconds and then it drops to 2000+ and starts going slowly down as engine heats up.

There is 1 idle hunting condition.

Just before engine is fully warmed up something goes strange.. it will start hunting idle 2000 -> 1000 -> 2000 -> 1000 .. this last about 30-90 seconds, then idle drops to 1300 and stays there.  (that is easy to answer the ECU wants to control idle at the 150F water temperature transistion point)
that is how this works not fully hot , the ECU knows only 1 thing here, that is to wakup the ISC and control idle at 800 rpm. (digital fast idle inputs all false)
That causes our cars here in USA to do the same thing and hunt (an illegal act that, and cured today) but not in 1991.

that hunt is pure ECU/ISC actions !!! and means the ECU is CONFUSED. and is 100% vacuum leak caused, or IAC leaking.
IAC leaking is also a vacuum leak, on 8valve. as is all others combined (they add up)



If I block my radiator and allow water to reach somewhere around 95C (200F) (approximation from temp gun pointed at stat housing giving ~90C () ) idle is less than 1000rpm (which is the limit for emission testing here, idle 1000 or lower or fail not caring what the tail pipe gives out).

I assume that either some TB gasket leaks, but I am more worried that its the 30 year old IAC and the rubber thingy is giving up.  (what is the rubber?)
2 years ago "normal" idle was 1100, now its 1300. So slowly creeping up. (ECU can not closes a 100% closed ISC, that be impossible so RPM is 1300 from leaks vacuum)
ISC is electric, IAC is 100% thermal only and IAC works just like a thermostat only the IAC is air only  controls)


Whether the car is on normal running temp (190F stat) or overheated with rad blocked, there is absolutely no reaction to adding engine load by turning blower to full blast, high beams on, seat heaters on, or even applying a bit of load via clutch or power steering. RPM goes down, no regulation. ISC does not care or is hacked.
I think you meant rpm falls with loads added and ISC is offline, or simply overloaded, IAC, means it is closed and huge vacuum leaks are the cause.

ISC does care in one situation and you guesstimated that some CARB guy has tampered with screws.
If I apply a little throttle (around 2500rpm on neutral) it will start hunting and RPM's bounce like 2500 -> 2300 -> 2500 -> 2300 and it continues for ever until you let the throttle go.

If forgot to tell you the cars outside USA have more fast idle digital controls. there, like head lamps on ? and other things?

(Tampering is quite probably, someone has tampered with electrics all around the car.. then removed some of them.. there are dead and live wires that are not connected to anything... so I assume the TB is also hacked/tampered).  all these cars have extra plugs not used, for options new 30 years ago never opted day 1.
Id have to see photos in color of each to tell what each does.  wire color codes are useful.




As I will need to anyhow order some parts from rock-auto I will also order new ISC (mine is 30 years old, so if its not bad yet, it will soon be). 2 sets of all TB gaskets in case I need to open the TB twice during fixing this issue. Not sure if I should order throttle valve position sensor. (TPS)
all gaskets there can be cut by hand with an exacto knife and blank gasket material. sure can and is easy and far far faster to do, MAIL and no custom forms nor any VAT.



Hoping I only need to place one order as filling in all the customs documents are nasty and time consuming as about every item has bit different tariff... and our value added tax is 24% 

So now my plan is this.

I will try to return all the adjustment nuts and TB clearance to specs you have on this site and hopefully get normal idle.
show photos  using Imagine link above, (old gallery is now Image) post them there and link them to here.
post back side of your TB. AND FRONT BOTH.
I am in texas our IAC is not like some there, in Europe,  different TB? not same distributor at all, there.

I do suspect my IAC is leaking a bit which causes abnormally high idle and that is something I will not be fixing as it would require new TB and there are none
The IAC IS TESTED EASY IN PAN OF HOT WATER, IAC CLOSES AT 150f  MUST. i EVEN DOCUMENTED THE IAC GAP IN THE CONE/SEAT OF IAC.

So if the IAC is shit:

1) Can I get hot idle fixed if I block the IAC port with clay or even epoxy from the TB. (Need permanent fix, not something that dissolves over time, hopefully clay would do.. easier to remove if needed).
THE ISC IS EASY TO BLOCK, ZERO CLAY AT THE BASE GASKET, BOCK THE IAC AIR HOLE. but saidly kills the front TB air bleed path too.
one guy here , defeated the now dead stuck open IAC doing this.
he defeated it 100%
then added a dash board air valve and vacuum line from it to any intake vacuum ports, on the actual manifold
the set idle using the dash knob. for cold starts he open said valve, by hand, then when water hit 150 closed it and the ISC then takes over. (ends the hunt too)
the human IAC, if you will.


2) Cold start needs to be hacked.
Scraping windows here is a must every winter day so I would rather spend the warmup time scraping instead of manually pressing throttle.

I have 2 ideas for this.

1) Hack a jamming device on the throttle you can use during warmup. Like press a bit of throttle and then jam the pedal / cable there, release before driving / after heating up.

2) Do electronic hack to DP via Arduino or something.. like take control voltage from current DP control voltage and extend DP operating period to NN seconds, or just manual on/off switch.

Question for part 2: Do you have any idea if the DP survives prolonged periods of active usage or will it burn?
the DP is only spring and a diaphragm. it also sends huge air to the engine its only purpose is to burn off cold start huge puddle of liquid fuel pooling up below TB in the manifold plenum.

While writing this.. option 3 came into my mind.. route a cable from cabin to engine compartment and put up old type of choke cable to pull the throttle/DP handle while the car is cold. (Tho I think its quite the same as option 1)

I really don't care how it runs cold as long as it stays running until warmed up and will not run too high RPM while hacked for warmup. This is mostly hobby car or 2nd car so it's not so important that you can hit the road right after startup.

make dash vacuum port.

if the IAC is bad, and finding 30 year old used one  is impossible, a for sure reality there.
here is what I'd do. same boat.
find a spare VSV valve, 12v.

with it in open mode  connect it to intake port vacuum
see if fast idle works with just it open, if too fast use restriction orifice. on the fresh air side of VSV.


using a VSV allows you to use a 12vdc switch to it and VSV under hood not  in the dash

the key here is any VSV (even generic) find one that at least has air flow (vacuum leak) to get
DP timed out, IAC is now 100%blocked, with clay or at gasket, hole missing on bottom of TB (cut a custom gasket)
cold fast idle at say 1300 to 1500 rpm for fast warm up
the throw the switch off when happy windows are now defrosting.

if 1500 can not be attained get a larger VSV, (vacuum solenoid valve 12v)

if the idle is too fast simply make a fresh air side of VSV with restricted  orifice. (using drills and dill the port until 1500 cold is hit.)



parting shot.  if the engine still races too fast with IAC blocked you are barking up the wrong tree and for sure hot pan of water test to TB passes. bark bark wrong tree.

idle too fast. hot.
1: turn the air bleed fully CW clock wise front edge of TB large screw near center line of TB.
this ends bleed air.
2;fails still , make sure TV is closed, even turn the screw on the throttle stop CCW (counter clock wise) intil TV is closed 99.999%) or .001" max gap TV. to bore.
3: still fails to get 800rpm pinch all air hoses. (or plug them) do not plug the map, inspect all map hoses by eye. carefully no cracks allowed,

4: make sure all ECU fast idle pins are at false readings per ECU page pin voltage same.

tradition for fast idle inputs
head lamps on.
PS overload switch stuck active, or wires shorted to it.
wires to rear glass defroster (if ever on car from new ever, must not be active on the wire named that. fast idle up.)
heater blower turned on , fast idle active.

USA 91 does not have HL or blower fast idle ever, some do in Europe. (and some Santana's of Spain)


the cold engine is 100% IAC VACUUM FLOW, (air) + TB bleed screw. if there, is it?