Car Stalls When A/C Turns On

[PhoenixRPR]

92 eclipse GSX. My base idle is set to 1,000 RPMS (purposely). When I turn on my car's a/c and then I roll to a stop, the car stalls. Help troubleshoot?

 

[flytalon93]

Sounds like your ISC is not functioning correctly.

 

[steve]

If he has a 1k idle (purposely or not) it's pretty sure that his ISC isn't working correctly.
Otherwise the ECU would force the idle back to 750. So the ISC is either broken or the BISS is so far out that the ISC is out of adjustment range. To get a 1k idle and have the ISC do what its designed to do requires ECU mods.

 

[PhoenixRPR]

My ISC is new from Mitsubishi. I verified that the ISC is functioning also. you can view my datalogger results here: http://www.dsmtuners.com/forums/showthread.php?t=130496

the BISS is set properly. I'm running at 1,000RPMS on purpose because if I set it to 750 and turn on the a/c the car will stall a lot more than if it's at 1,000. So if you see that my ISC is stepping when the ISC is turned on, what can the other problems be causing this?

This is a false statement: "To get a 1k idle and have the ISC do what its designed to do requires ECU mods." The ISC is not at all responsible for where your car's base idle is set. The ISC simply adjusts for loads on the engine.

 

[crankbender]

My ISC is new from Mitsubishi. I verified that the ISC is functioning also. you can view my datalogger results here: http://www.dsmtuners.com/forums/showthread.php?t=130496

the BISS is set properly. I'm running at 1,000RPMS on purpose because if I set it to 750 and turn on the a/c the car will stall a lot more than if it's at 1,000. So if you see that my ISC is stepping when the ISC is turned on, what can the other problems be causing this?

This is a false statement: "To get a 1k idle and have the ISC do what its designed to do requires ECU mods." The ISC is not at all responsible for where your car's base idle is set. The ISC simply adjusts for loads on the engine.

Incorrect. The ISC should be adjusted by the ecu to obtain an idle RPM of 750 +-50. (may vary by 50-100 in diff models). If you are idling at 1000, not idle surging when rolling, and stalling with the ac on you have a problem with the idle control system in your car. The most obvious place to look is the ISC but next would be the ECU.

It is possible that you have one of the plugs backwards. Some of the vehicles have 2 plugs that will both fit the ICS right there....make sure you are on the right one.

Have you checked your plugs yet. It appears to me by the log that you might not be firing correctly on all cylinders. How does the car run wot? Do you have any other problems. It may be that your ac compressor is bad also.

Still odd that you have your idle all the way up to 1k...it shouldn't need to be there. maybe that is maskin the real problem....

 

[thegame]

I have the same problem, if the a/c or the defrost is running it bogs the motor down and vigorously shakes the care like its trying to take my lunch money. I know that I need new belts so I haven't invested alot of time into troubleshooting. However another thing that mine does is jerk when put into drive, like it needs to rev up a little then it engages and jerks. Maybe this is ISC related as well?

 

[SwiftKidGSX]

I USED to experience the same problem you had and though that it could be the cams that is throwing off the rpm way out of spectrum when I hit the A/C. Anyhow with in time it seemed the symptom was improving and now I don’t have the problem...this is my theory...the computer has to learn this new curve. What I would do when I had my A/C on and was going to stop was press the A/C button off first when I was going take it out of gear and once the RPM's where at idle would then I press the A/C button back on... with in time I didn’t have to do this anymore... I think this happends because the RPM's drop so quickly when the A/C that it just dies.

Food for thought.

Joey 99GSX

 

[steve]

This is a false statement: "To get a 1k idle and have the ISC do what its designed to do requires ECU mods." The ISC is not at all responsible for where your car's base idle is set. The ISC simply adjusts for loads on the engine.

I humbly suggest you read the technical information manuals on Idle Speed Control.

When correctly setting the BASE idle speed the ISC position is locked in it's default position by grounding the timing check and diag mode connectors on a 1G or by using the scan tool actuator test on a 2G. Then the idle speed is adjusted using the BISS. This takes into account the air being bypassed by the locked ISC. Since the ECU is programed to maintain a 750 rpm curb idle speed, as soon as you unlock the ISC the ECU will attempt to adjust the speed to 750 by moving the ISC pintle in or out. The only way you can get a 1k idle with a stock ECU is to drive the ISC out of range closed so that the ECU can't compensate and lower the speed.

So, "To get a 1k idle and have the ISC do what its designed to do requires ECU mods." It's the only way the change the target speed the ECU will attempt to regulate to.

Steve