89/90 sidekick idle speeds 800/920rpm

[spiritofr]

I think I finally understand now, I need to:

1. Clean the ISC and set its duty cycle to 50% using a scope or DMM on 20vdc scale--with the scope or DMM on the ISC turn the TV stop screw until the scope shows a symmetrical wave form or multi meter shows 7vdc.

2. Clean and calibrate the TPS to 0.086" gap between the screw and stop lever.

I will also make sure there are no vacuum leaks in the air lines and make sure the EGR is clean and working, and check the fuel system for any issues.

[fixkick]

(very good list) the gap is set and the TPS rotated until it drops below 300ohms (switch side)
yes, old cars leak air.
they can spring vacuum leaks.
and will never idle correctly if the leak exceeds the ISC controls.
some leaks are very hard to find. (even internal TB cracks in TBI engine)

[spiritofr]

Thanks!

Where exactly is the TPS adjustment screw and stop lever, where I need to gap 2.2mm?

[loper12]

thanks for the post very useful and helped me alot with my car.




mercedes-benz service

[fixkick]

the 89/90s are a royal pain
they must be done concurrent with dutycycle.
in 1991 this "comedy" ended.

messing one , messes up the other , comedy.

[spiritofr]

Hi Fixkick,

On your TPS calibration page, the FSM step 3 says to rotate the TPS until ohms change from 0 to infinity, but on this thread you said to rotate TPS until ohms drop below 300, which is it? Or is this basically saying the same thing because it never gets to 0?

Thank you!

[fixkick]

yes, actually we move it both ways to find the point that it just closes the switch.
if you over travel it, in to closed position, the switch will delay opening,. driving.. and cause ecu to go tad nuts, at throttle tip in,,, hesitate....
that is correct, it's really carbon. and can not reach zero like a normal real gold switch can do easy.
we think the spec. is 300 ohms to you, but 500 to the ECU. (but is speculation that)
for sure get the value below 500 ohms by hand closed with the feeler gauge. the 89/90 is a real pain to do , because after done idle duty cycle will be wrong. then you set idle and then the switch is now set wrong, yes, true pain there and cured in 1991 for ever..

i have the real FSM pages annotated here.

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

it says zero continuity, in the fsm, this is clearly wrong, it should say, (low ohms) and low is defined as below 500, 300 is better IMO.
I try to get it below 300, just a tad. but 500 is ok too. and is spec....

it will never get zero ever. due to carbon based switch contacts.

the ECU uses voltage to detect this trip point, and is a vary low voltage. (a secret) my guess 0.5v?
when the ECU sees the low voltage it, goes to idle mode. instantly.
and ISC wakes up. and regs. (and EGR is cancelled, etc)

also the old engine ,the TPS is set with no using 3 feeler gauges. this invites errors. (human)
some TPS go like this
50 ohms, rising as you turn pot. to 1000 ohms then go to infinity, in and instant. (try it see how yours varies then hits the open cliff of infinity)
that being true, the 500 is about center of this range.

[spiritofr]

Thanks Fixkick, as always I appreciate the help. My TPS goes from 30-50ohms to about 1000/1100ohms and then infinity. I will try to get it to around 300-500ohms.

Questions about the ISC connector:

- You said I should check the blue/black wire for 12V, can I just probe the front or do I have to backprobe using a needle probe? Should the connector be disconnected or connected when I do this?

- When doing the cheater duty cycle, i.e. backprobing the ISC pins with a scope or good DMM at 20Vdc, do I backprobe the ISC side (red and green wires) or the other side (blue/black and green/black wires)? And do I probe with the connector disconnected or connected?

Sorry if these are no-brainers, I am a newbie trying to learn my away around this 1.6L 8V TBI

[fixkick]

your welcome, and glad to help.
yes, the ISC drivers

you can just use A dmm meter set to volts, and set it to 7v. 1/2 battery running.
if the meter dont mess that up, that is, as some do.
yes, the isc needs to be connected.
and in all cases back probed. the meter do both pins with needles.
its a 5 volt square wave signal there.
if if using a scope I just probe one side or the other and see the 5v signal.
I think one side is ecu ground but cant remember the color.
i should have took more readings with my scope, and got lazy.
but this solenoid does pulse 200 times a second, real fast.

that is a great TPS there...

[zukitrek]

I never did this to my 94 16V. How different is the steps in mine and does my regular DMM will work?^^^^

you can just use A dmm meter set to volts, and set it to 7v. 1/2 battery running.
if the meter dont mess that up, that is, as some do.
yes, the isc needs to be connected.
and in all cases back probed. the meter do both pins with needles.
its a 5 volt square wave signal there.
if if using a scope I just probe one side or the other and see the 5v signal.
I think one side is ecu ground but cant remember the color.
i should have took more readings with my scope, and got lazy.
but this solenoid does pulse 200 times a second, real fast.

that is a great TPS there...