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TPS, can it be adjusted with a cold engine?; TPS
Topic Started: Apr 8 2018, 08:34 PM (161 Views)
Mrbreeze


Ok, I was wondering if I could just unplug and remove the ISC motor from the daughters 99 and then dial the TPS in, with the ISC motor removed for this procedure I don't see what the purpose is to get the engine up to temperature, unless I'am missing something? Would like to hear your thoughts on this, thank you..
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suzukitom
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Tom

the ISC motor plunger will gradually retract when rhe engine warms up so that the throttle lever will be resting on its stop.

At this point you need to insert the feeler gauge per FSM instructions in order to set the TPS.

unplugging and removing the ISC motor may save you the few minites it takes for the engine to warm up and retract the ISC plunger.
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Mrbreeze


Thank you, thank was my logic, the plus side of that is I don't have to work on a hot engine when it's already 97 degrees outside..
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Mrbreeze


Ok, I got the TPS set to.98v with a 9/64 drill bit, good throttle response, the "lag" has disappeared, that's a good thing, haven't test driven it yet,but now it almost won't idle,it's so low that the battery light comes on.. the question I have is I know it's taboo to energize the ISC motor when it's not connected to the throttle body, but if you were stepping on the throttle before you turned the key to the on position wouldn't that be the same thing? I haven't noticed the ISC motor doing much of anything, it's making contact, but that's about it, I'll test drive it in a day or so and update this thread then, if anyone has any ideas or a similar experience I'd love to hear about it, thanks guys..
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Metromightymouse
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Powdercoat Wizard

Mrbreeze
Apr 13 2018, 12:47 PM
Ok, I got the TPS set to.98v with a 9/64 drill bit, good throttle response, the "lag" has disappeared, that's a good thing, haven't test driven it yet,but now it almost won't idle,it's so low that the battery light comes on.. the question I have is I know it's taboo to energize the ISC motor when it's not connected to the throttle body, but if you were stepping on the throttle before you turned the key to the on position wouldn't that be the same thing? I haven't noticed the ISC motor doing much of anything, it's making contact, but that's about it, I'll test drive it in a day or so and update this thread then, if anyone has any ideas or a similar experience I'd love to hear about it, thanks guys..
The ISC is limited by the throttle lever and can't overextend. If it is run without anything to stop it from over extending it screws something up and for me, no amount of taking it apart and realigning it would fix it.
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suzukitom
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Tom

Metromightymouse
Apr 13 2018, 02:47 PM
Mrbreeze
Apr 13 2018, 12:47 PM
Ok, I got the TPS set to.98v with a 9/64 drill bit, good throttle response, the "lag" has disappeared, that's a good thing, haven't test driven it yet,but now it almost won't idle,it's so low that the battery light comes on.. the question I have is I know it's taboo to energize the ISC motor when it's not connected to the throttle body, but if you were stepping on the throttle before you turned the key to the on position wouldn't that be the same thing? I haven't noticed the ISC motor doing much of anything, it's making contact, but that's about it, I'll test drive it in a day or so and update this thread then, if anyone has any ideas or a similar experience I'd love to hear about it, thanks guys..
The ISC is limited by the throttle lever and can't overextend. If it is run without anything to stop it from over extending it screws something up and for me, no amount of taking it apart and realigning it would fix it.
There is a functional ISC motor test involving a 1.5 volt battery, (this low voltage is intended to limit potential damage to the motor during a brief test) but this test is ordinarily not done unless it is suspected that the ISC motor has failed. In my experience, the motor itself rarely fails, and junkyard ISC motors pulled from cars with high miles still work fine.

On a 1999 Metro 1.0, the ISC performs 2 functions. The motor plunger moves to adjust the idle speed higher or lower as needed to control idle speed under cold start conditions, or whenever a heavy electrical load is switched on with the engine running. The other function it performs is to detect when the throttle plate is closed, ie. at an idle position. To do this, the ISC plunger is integrated with an internal idle switch. If you have the ISC assembly unit in your hand, you can feel the idle position by depressing its plunger. The first 1/4 inch of plunger travel has spring resistance, and then it firms up and stops. This is where the idle switch sends a signal to the PCM to indicate that it is in an 'at idle = TRUE' state. Under normal conditions, whenever the engine is idling without your foot on the gas pedal, the ISC plunger will overcome the 1/4 inch spring travel and the plunger tip firmly rests against its ISC plunger stop. If this internal idle switch has failed electrically, or the plunger is not quite in its 'at idle = TRUE' position, then the PCM will not command the ISC to control the idle speed, as the idle input signal indicates the throttle position is NOT at idle.

It is more likely that wear has gradually caused the ISC motor plunger tip, and/or the throttle plate to be slightly out of position for the ISC plunger to be in its 'idle=true' position. You can compensate for this wear, by adjusting the throttle plate, or temporarily by inserting a thin object such as a dime between the ISC plunger and the ISC plunger stop. If the ISC motor does not come to life, it may indicate either a wiring problem, internal switch failure, or the ISC motor has failed.


[Edit: one more thing to add. If a new ISC unit is bolted in, or if the battery has been disconnected for a while and hooked back up, you may notice that the PCM seems to command the ISC to hunt around a bit as it attempts to re-orient the ISC plunger and find and maintain the correct idle speed. ]
Edited by suzukitom, Apr 13 2018, 03:30 PM.
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Metromightymouse
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Powdercoat Wizard

In my case, my idle was a little strange at times if I remember correctly, I had taken it off the throttle body and started the car and it fully extended the plunger and made awful noises. When I took it apart and reset the plunger it never worked right again, idle would be all over the place. When I replaced the isc it woked fine.
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Mrbreeze


Ok, making progress, I failed to mention that while I had the TPS off I took it apart, thought I'd give it some grease cause it was looking a little dry, I screwed the plunger all the way in and out several times, added grease to the sides of the white plastic cup of the plunger, screwed in and out, unscrewed it a couple a turns than put it back together and installed it back onto the throttle body, started the car and it wouldn't idle.. so I had a bright idea after I got home from work this morning, last year when I changed the battery and fired it up I had the front end on a jack and it was kind of "hunting" because the VSS was getting a signal that the car was moving and I could see the ISC motor working, so I thought I'd try that, it didn't work.. so I thought what the heck, I do know when you disconnect the battery, the car goes through a learning process for driving habits, and guess what? The ISC motor came back to life, haven't driven it yet, but it's idling now and when I turn the blower on one of the low speeds or turn the running lights on, it idles up
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