Ion Posted June 13, 2009 Report Share Posted June 13, 2009 Due to ongoing random stalling issues with my '94 Eldo, I described this to anyone who would listed, in an attempt to find a means to an end. After speaking only a sentance or two about the northstar randomly stalling, mostly when it was hot outside and I had the ac running (previous post is here: http://caddyinfo.ipbhost.com/index.php?showtopic=22023), he immediately said it was an old, corroded IAC motor at the root of the problem. Big question here: does this car have an IAC motor? If so, is it where most are located, on or near the throttle body? If yes, why has noone, including alleged cadillac specialists, been able to suggest this? Link to comment Share on other sites More sharing options...
lothos Posted June 13, 2009 Report Share Posted June 13, 2009 I think your car has the Idle Speed Control (ISC) motor like mine does. It's a small motor located near the throttle body and the cruise control. I'm a newbie and I replaced mine without too much trouble. After you turn the car off do you hear a clicking noise coming from under the hood, and does the gas pedal move up and down rapidly? WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn. Cheers! 5% discount code at RockAuto.com - click here for your discount! Link to comment Share on other sites More sharing options...
Ranger Posted June 14, 2009 Report Share Posted June 14, 2009 I think your car has the Idle Speed Control (ISC) motor like mine does. It's a small motor located near the throttle body and the cruise control. I'm a newbie and I replaced mine without too much trouble. After you turn the car off do you hear a clicking noise coming from under the hood, and does the gas pedal move up and down rapidly? Correct. Link to comment Share on other sites More sharing options...
Ion Posted June 14, 2009 Author Report Share Posted June 14, 2009 I think your car has the Idle Speed Control (ISC) motor like mine does. It's a small motor located near the throttle body and the cruise control. I'm a newbie and I replaced mine without too much trouble. After you turn the car off do you hear a clicking noise coming from under the hood, and does the gas pedal move up and down rapidly? No...never had pedal issues or clicking noises. Link to comment Share on other sites More sharing options...
Ion Posted June 14, 2009 Author Report Share Posted June 14, 2009 I think your car has the Idle Speed Control (ISC) motor like mine does. It's a small motor located near the throttle body and the cruise control. I'm a newbie and I replaced mine without too much trouble. After you turn the car off do you hear a clicking noise coming from under the hood, and does the gas pedal move up and down rapidly? Correct. Ranger...could this gizmo cause the issues I've been having? Link to comment Share on other sites More sharing options...
adallak Posted June 14, 2009 Report Share Posted June 14, 2009 Due to ongoing random stalling issues with my '94 Eldo, I described this to anyone who would listed, in an attempt to find a means to an end. After speaking only a sentance or two about the northstar randomly stalling, mostly when it was hot outside and I had the ac running (previous post is here: http://caddyinfo.ipbhost.com/index.php?showtopic=22023), he immediately said it was an old, corroded IAC motor at the root of the problem. Big question here: does this car have an IAC motor? If so, is it where most are located, on or near the throttle body? If yes, why has noone, including alleged cadillac specialists, been able to suggest this? I do not see (and probably neither others do) why ISC motor would act up only when it is hot outside. But your competent source, which calls ISC motor IAC motor might know better. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Ion Posted June 14, 2009 Author Report Share Posted June 14, 2009 Due to ongoing random stalling issues with my '94 Eldo, I described this to anyone who would listed, in an attempt to find a means to an end. After speaking only a sentence or two about the northstar randomly stalling, mostly when it was hot outside and I had the ac running (previous post is here: http://caddyinfo.ipbhost.com/index.php?showtopic=22023), he immediately said it was an old, corroded IAC motor at the root of the problem. Big question here: does this car have an IAC motor? If so, is it where most are located, on or near the throttle body? If yes, why has noone, including alleged cadillac specialists, been able to suggest this? I do not see (and probably neither others do) why ISC motor would act up only when it is hot outside. But your competent source, which calls ISC motor IAC motor might know better. Here's how it was 'splained to me: When an Idle Control Motor (he was not car specific, he spoke in general terms and thus was 100% accurate in identifying the part) is old and begins to get gunk buildup arond the piston, it cannot function normally. So when the car's computer senses a new load, in my case, ac being turned on "when it is hot outside", it sends a signal to the IAC to alter the mix to compensate. When the piston's movement is restricted, it cannot properly carry out the task sent to it by the computer and causes engine to stall. This is factual, documented information whereby cleaning or buying a new IAC has remedied intermittent stalling issues on cars he has worked on. Since I have been f-ing with this scenario for 2 years running and noone here or local garages has been able to properly diagnose the source of the problem, I was open to new suggestions... Now onto something that's hopefully productive: Does an ISC perform the same function as an IAC? If so, might the above description (gunked up piston, affecting it's abiltiy to excecute commands from computer, causing stalling) be the mysterious, elusive root of my car's problems? Link to comment Share on other sites More sharing options...
KHE Posted June 14, 2009 Report Share Posted June 14, 2009 The IAC has a plunger that moves in and out in a small passage in the throttle body to increase or decrease air into the mix. The ISC system on the older cars is esternal to the throttle body and uses a motor to open or close the butterfly valve. Your 94 car uses the ISC motor which wouldn't have the same failure mode as what you described for the IAC. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
EMFI2R Posted May 13, 2015 Report Share Posted May 13, 2015 Hello everyone! New member here... I think my mother-in-law's 1991 Cadillac Deville has this exact same "ISC" problem! When it's a cold start, the engine hisitates (like lagging/bad fuel) but runs better wafter a while. Afterwards it gets up and goes! AND... Every time you shut it off, there is a pump noise from the engine compartment for a while, and the gas pedal bounces rapidly up and down a bunch of times. She took it to her mechanic. His fix? Turn up the idle! It still does it. I thought maybe a vacuum leak, but finaly found this thread. Do you think the ISC is the issue? Thanks! Link to comment Share on other sites More sharing options...
KHE Posted May 15, 2015 Report Share Posted May 15, 2015 The '91 Deville has an idle speed control motor, not an IAC valve. If it is making racheting noises, the contacts for the closed throttle switch are bad. You can take the unit apart and clean them or replace the unit and adjust it. There is a ton of information in the archives on the idle speed control. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.