Vitara 1991 brake booster replacement

[fixkick]

CEL light ok on power-on engine stopped. All lights go away on startup. I read error codes at spring just ok (code was if I remember ok 13 - bad O2 sensor).

I have recently changed (related to points you said):
- spark plugs, RAD, fan clutch, STAT (190F), O2 sensor

Engine runs very stably without vibration unless I remove the plug from booster's vacuum hose. When I do that, it vibrates a bit until it ups RPM to 1400-1500 no vibration then. When I put the plug back it drops to 1200rpm, no vibration.

My fuel usage was on fast paved road travel about 8,3l / 100km (around 28mpg) and when driving only 80-90km/h (50-55 mph) it was around 7,5l/100km (31mpg). So I am guessing spark is ok, so is lambda and not in limp mode. Also it feels that all power is present. I did drive 130+kmh (80mph+) on motorway so definitely all power is present as its about the suzuki spec topspeed.

I think my ISC is busted, but before clutch replacement hot idle was 800RPM and when putting lots of electrics on it went down 600 RPM. But this high idle of 1200 RPM started after clutch replacement and some welding done on back of the frame (they had to drop tank).

So my best guess is that when tilting engine and doing other stuff some very bad rubber hose broke a bit.


One thing I have noticed. WHen engine is hot (STAT open) and I press lightly throttle, RPM goes slowly upto 2500 and then drops to 2300 and then it does that 2300->2500->2300... for ever until I press more throttle. Some strange cutoff error there. I guess the EFI changes mode there and gets confused.

So anyhow I think I will first just change all the hoses as they are anyways going to break very soon. Then if the problem persist, check other things.


I fear that some previous owner has done a lot of nasty things there. There are DIY electric fixes here and there, like they had at somepoint bypassed the fuel pump relay and then switched back to the relay. ALso could be that somebody has tampered with the EFI "do not touch nut".. as the HOT side knob for tuning something (that has AISIN brand text there) is broken off. Cold side knob exists.

So the car is bit of a mystery.

thank you for the update.

so this ISC looks like this.  our TB is made by Mukni.



the ISC is here, note the ECU side plug not seen on 89/90 years here. (early year is 2 pig tails wires)
the 5mm Allen wrench hex screw , also a never touch screw but when very old we do adjust it as inside is rubber seat that gets worn and leaks.
when that Happens I set the screw so the piston inside just touches the, seat gently.
the 4th screw, (is air bleed screw the correct name is Duty cycles setting , and is set to the the IAC is at 50% duty at hot 800 rpm.

91 USA version.  91-95 in USA TBI (aka. SPI, single point injection)





Does your ISC look just  like this?

see stamp Mukuni on IAC housing?  note the white painted never touch screw, some are plastic capped over. that is the factory .0005" TV gap/bore setting. only.

The DP  screw is for setting  only the dashpot idle speed,. hot. started to 2500 rpm. (active only at first start of engine for 3 to 15seconds DP actions only)







there are ways to block hidden air paths the IAC to see if it leaks hot. IAC is thermal only cold idle.


 or simply us pan of hot water to be sure it closes as I did here.  I did this with drill bit  shanks, as feeler gauges.

before doing all this, above, we make sure all hoses vacuum do not leak end to end.

also you stated one more problem above.
"RPM goes slowly upto 2500 and then drops to 2300 and then it does that 2300->2500->2300.."
this wrong, and I know that cause. (assume booster hose plugged and no other vacuum hose cracked wide open and changing illegal air flows via normal vibration)

this is the TPS idle switch set wrong. the ISC must go off line with right foot pressed, on your car it is set wrong, and the ISC is wrongly active fighting the right foot actions. 


The idle switch is set. to. .016" (0.4mm) (throttle cable free play must not be zero, 10mm is spec  on able)
the no touch screw rear lower must not be wrong or molested.  0.0005' gap in TV bore.
then we set the air gap on that screw with .016" feeler gauge.
then set the TPS idle pins to go to open circuit at .016"

step1 https://fixkick.com/TPS/TPS-p91.JPG

step2  https://fixkick.com/TPS/TPS-p92.jpg

step3 https://fixkick.com/TPS/TPS-p93.JPG



links to my TBI slide show are here.