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when in my 92summit, every once in a blue moon i stall because of rough idle when the ac is on(an essential in az) some times in dangerous positions like pushing the clutch in on a turn , the car idles fine w/o the ac on in fact i have a mirage and it idles more smoothly than that(but is usless w/o tranny) i was wondering if a motor or vacum or sensor controling the ac idle is malfunctioning, or (i doubt it but the goodyear guy said it could be) my ecu. by the way everything else runs perfect(except its a 1.5) jk

Don't they have a switch or signal, to tell the ECU to idle higher when AC is engaged?

Yes they have such a switch. I forgot what ECU pin it was and if it has to be grounded or 12 V applied to tell the ECU the AC is on.
When idling normally, does the idle speed increase or decrease when you switch on the AC? Manual cars usually rise the idle to 950 revs or so w/ AC on.

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Got rabies?

The ISC controls idle. When you turn the AC on, you should notice the idle raise slightly to compensate the additional load. You can adjust the ISC to idle higher under load. One prob ive noticed tho. Since all the mods on my car, i cant get it set quite right. If i set it to idle at proper rpm while AC is on it'll surge whe the AC is off. If i set it to the point where the surging stops, then i have the stalling problem. Ive tried new sensors. Same prob. Could be that now my RPM drops too fast for the sensor to catch it in time. I'm gonna recalibrate the tps and all sensors to factory specs and see if it helps but am doubtful. Could require custom fitting a anti-stall pot like on carb cars.

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http://members.cardomain.com/socrateez
04' Olds Alero
91' Colt GL hatchback
4g15 12valve 5spd.
4g37 TB, MAF & Injectors. 4g37 ECU
Ported & polished & custom CAI w/K&N filter
5* Cam retard, 7*Ignition advance
2-1/4" catback w/flowmaster muffler
89 GT brake and suspension swap
Lots of little s#@t

where is the isc, how do i modify it, any pics will help for this also i would like to note that my car is completely stock right now

The ISC is right below the throttle body. If you look into the engine compartment, it is in the middle of the engine and near the firewall. It is right where that really big hose from the air cleaner meets that metal part with "ECI multi" written on it.

I guess socrateez played with the SAS (the amount how much the throttle is opened when you don't have your foot on the gas pedal). Hey socrateez how did you adjust your ISC? I forgot how to do that on a 4G15. Was so damn easy on my 4G67.

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Got rabies?

The ICS is on the side of the throttlebody facing the firewall. Its the larger sensor. there are two screws. one adjusts base idle and i believe is mounted to the throttlebody housing and is easy to see. The other is on the throttle cam and adjusts the ICS and sits lower down you have to look directly over the throttlebody to see it. With the AC on turn the screw in and the idle should raise.

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http://members.cardomain.com/socrateez
04' Olds Alero
91' Colt GL hatchback
4g15 12valve 5spd.
4g37 TB, MAF & Injectors. 4g37 ECU
Ported & polished & custom CAI w/K&N filter
5* Cam retard, 7*Ignition advance
2-1/4" catback w/flowmaster muffler
89 GT brake and suspension swap
Lots of little s#@t

Evo, I had the same problem with my '92 summit 4g15. I had to raise my idle. the downside to this is that it's rpms are really high when I dont have my AC on. Damn Arizona sun!!!!! Where are ya at exactally? Tempe here :-p

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01 Maxima VQ30DE
92 Summit 4g63t (Traded to Evo... R.I.P.)

I had the same exact problem on my 92 mirage. with a/c on, when I come to a stop. car would shake, idle erratic like it would quit. but when I accelerated, it's fine. However with the a/c off, no erratic idle at all when coming to a stop. I didn't do anything for a year or two and just drove the car without the a/c. then all of a sudden, my engine idle was shaking erratically at a stop with the a/c off like my engine was going to die. Here's what I did. I thought it was the ISC motor going out. But I did the cheapest thing I could find..I grabbed an old toothbrush and a 70 cent can of carburetor cleaner and sprayed the throttle body and scrubed the black gunk around the throttle plate. Waaalahh!! no more erratic idle at stop signs anymore. Even better, I run my a/c now with no erratic idle at stop signs. only cost me 70 cents to fix it!!

If you guys can find an old Ford V8 with A/C wiring, there is a solenoid that is turned on when the A/C is kicked in; solenoid pushes a rod that in turn pushes the throttle bracket to a high idle. If you make up a bracket and a switch or run from the wiring in the dash switch or from a relay then you can trigger the solenoid to raise the idle manually. You would have to make a bracket and or watch the ECU go through little fits trying to accomodate the changes but then you will have a high enough idle to keep the engine breathing! Ghetto fab +1 , Honduh 0