unstable idlling-stalling im going nuts

I feel your pain...there are so many hits about this issue but no real definite resolution. Our TW went merrily for a couple of years and then one day we began having the random drop in idle while waiting at traffic lights and/or stalling. It starts immediately and off you go. I have cleaned the throttle body and ISC, reset the ECU and all runs sweetly for 3 or so weeks and then within a few days all the issues creep back. Most times the reset temporarily works but in recent weeks it hasn't. I purchased a new ISC and it basically did zip other than it introduced a new issue by having a consistent low idle speed for the first week (even at cold start where you had to keep the revs at 1,000 RPM for 30 seconds for it to have a stable idle) then one morning it went up to 1200 RPM on its own ! Our local road service guy suggested that if it does not become stable with the new ISC then I should look at replacing the ECU from an identical model (TW wagon Series 2 with tiptronic 4 speed trans).....it's a good car but geeze if I new of a reputable Mitsi specialist in Adelaide I'd be happy to throw some dollars at it.

Damn....

i had a go with it just now.. but i wasnt fully test it properly as the ****ing bottom screw snapped a piece and i couldnt open it, the gap next to the screw is too narrow to use a socket.. anyways
before tampering with it i tested it using the continuity method as described in the manual you linked, i noticed that it is ok usually but if i pull the throttle wire up and suddenly drop it sometimes continuity wasn't there, pull again drop again and works..
i was able to move it clockwise with a bit of force and continuity is stable. idling seems better now but need to observe and report long term result.
i also noticed if i tap on the sensor while continuity is on, it interrupts it. maybe sensor is dodgy.. maybe forcing it i buggered it who knows.

thank you for the great advice and follow up

Could be the problem, it would certainly explain the dodgy idling. There are a couple of things that could be the cause other than a cactus TPS, such as gunge in the TB fouling the butterfly valve or too much tension on the throttle cable. Otherwise if you can't get a stable closed throttle position on the TPS I'd look at replacing it.

Quote:

Originally Posted by GRH

i had a go with it just now.. but i wasnt fully test it properly as the ****ing bottom screw snapped a piece and i couldnt open it, the gap next to the screw is too narrow to use a socket.. anyways
before tampering with it i tested it using the continuity method as described in the manual you linked, i noticed that it is ok usually but if i pull the throttle wire up and suddenly drop it sometimes continuity wasn't there, pull again drop again and works..
i was able to move it clockwise with a bit of force and continuity is stable. idling seems better now but need to observe and report long term result.
i also noticed if i tap on the sensor while continuity is on, it interrupts it. maybe sensor is dodgy.. maybe forcing it i buggered it who knows.

thank you for the great advice and follow up

A "thin wall" quarter inch drive 8mm socket will fit, whereas a regular half inch drive 8mm socket will not.

Quote:

Originally Posted by Ensoniq5

Could be the problem, it would certainly explain the dodgy idling. There are a couple of things that could be the cause other than a cactus TPS, such as gunge in the TB fouling the butterfly valve or too much tension on the throttle cable. Otherwise if you can't get a stable closed throttle position on the TPS I'd look at replacing it.

hi again
as i was checking where to buy the TPS i came accross another part that is commonly associated with bad idling.. site had it listed as idle air control motor, IAC, now i found something looks like shown under the throttle body, looks exactly same, tho i thought this was also called idle speed motor and that's the one previous owner had replaced. i can see the part nice and shiny and it looks new. however, not knowing how to test it, i pulled it's plug while car was idling and noticed no effect.
i turned off the engine and started again with this cable unplugged and again noticed no difference in idling at all.. ac on off, put in D etc.. its exactly doing same thing as it is doing with this cable plugged .
i'm a bit puzzled... the connector plug looks clean inside too... is it possible new part is faulty? or any other possibility?
shouln't idling change when i unplug this ?

this is the part https://www.ebay.com.au/itm/IAC-for-...YAAOSwqGlat8Bo

No, idling is unlikely to change immediately by unplugging the ISC since it's just a valve. Unplugging it won't cause the valve to suddenly move (quite the opposite) so no change to the idle speed would be expected. However it should change when switching AC on or off to counter the extra load BUT ONLY if the throttle closed switch has told the ECU the engine is idling. If not, the ECU is trying to run the engine based on sensor readings (MAF etc.) and the ISC isn't in the loop at all. You will need to fix/verify the TPS before you can know whether the ISC is working or not.

hmm makes sense. i guess in this case only way to fully verify the tps is to probe it while its plugged and engine running and see if the engine vibration messes up the continuity or not.
i ll be on it tomorrow

ok i was able to open the buggered screw with a good tip from neighbour , grinded the edges of a cheapy socket.
sensor works but doesn't seem very stable. for instance, in continuity test, i read 30-90 ohms while i still have the beep, pulling the throttle wire slowly ohmage increases gradually but even when the beep stops ohmage continues to rise to around 240-300 ohms before reading turns to OL . near the beep limit if i pull the wire very slowly at some stage beep stops and starts again, it almost feels like the switch was stuck on borderline limit and got corroded over time. idling is better now after adjustment. i didn't have any feeler gauge etc.. but gave it a bit headroom and adjusted it while engine was idling, found the sweet spot where engine reacts to throttle and set it there.

i ll see how it goes.. not a cheap part for how small the bugger is. might get one if acting up continues. thanks for the help guys

Here is some more information about TPS from an earlier thread:

https://www.aussiemagna.com/forums/sh...t=92836&page=1