: can't find anyone who knows the answer



samicaddy
08-04-07, 06:28 PM
my dad just passed away and now i've got his '94 Cadillac STS with a northstar sometimes the car doesnt want to return to idle when I come to a stop if I put he car in neutral it jumps and revs to about 2000 i will give it some gas and it will return to normally idling speed. this happens pretty frequently. i dont know much about cars so anything you guys can tell me would help. thanks!

Ranger
08-04-07, 07:52 PM
My guess would be a faulty ISC (Idle Speed Control) motor. Have you checked the codes?

samicaddy
08-04-07, 07:58 PM
no, how do you do that?

Zorb750
08-05-07, 09:04 AM
Hold the Off button and the Temp+ (Red) button down on the climate control panel to the right of the gauges until everything on the display lights up, then grab a pen and start writing, quickly!

parts68
08-05-07, 06:35 PM
Sorry to hear of your fathers passing
Keeping his car up will please him.
I agree that the Idle speed Device would be the first step.
Its not the easiest to replace but you can do it.
Be sure and follow the directions supplied on the plunger adjustment.
You will also need to do a driving cycle to reset it.
Cheapest Ive found is autozone for $55.

zonie77
08-06-07, 09:44 AM
Cleaning the throttle body should be first. I think there's instructions in tech tips. Basically pull the intake hose off and clean the throttle plate on both sides. It's probably coated with an oily buildup.

Carb cleaner , rags, and a toothbrush would do it.

codewize
08-06-07, 02:35 PM
As reinforcement, this would be my first guess too. I've been through this with my 89.


My guess would be a faulty ISC (Idle Speed Control) motor. Have you checked the codes?

samicaddy
08-07-07, 10:11 AM
Alright, so I ran the codes and this is what came up.....

P034 - MAP Sensor Signal Out of Range
P043 - Left Oxygen Sensor Signal Rich
P045 - Right Oxygen Sensor Signal Rich
P052 - PCM Memory Reset
P071 - Intermittent MAP Signal
P095 - Engine Stall Detected
P109 - Keep Alive Memory (KAM) Reset/PCM has lost primary battery power
I052 - Keep Alive Memory Error

These all said history after them as well. Anything based on these codes?

I'll call around about getting the ISC replaced. I'm kinda afraid to do it myself, with my luck I'll mess it up more than it already is, haha!

Ranger
08-07-07, 10:35 AM
ISC motor is pretty easy to change.

If all those codes are historical, clear them and see what returns.

codewize
08-07-07, 11:18 AM
It's pretty simple to replace the ISC BUT getting it calibrated correctly takes some reading. If you're going to do this yourself let me know and I'll post the instructions for calibration. It's not difficult it just takes patients.

samicaddy
08-07-07, 01:04 PM
so, if i were to do this by myself, how would i go about replacing the ISC?

samicaddy
08-07-07, 01:07 PM
oh yeah and another question...could the Idle Speed Control also be the reason why the Service Engine Soon light came on? it just turned on for the first time today.

codewize
08-07-07, 02:16 PM
Definitely. It may even go on and off intermittently. The ISC is the plunger thing on the side of the throttle body. Unbolt it and bold the new on on.


oh yeah and another question...could the Idle Speed Control also be the reason why the Service Engine Soon light came on? it just turned on for the first time today.

Ranger
08-07-07, 03:30 PM
After you replace it, it needs to be adjusted. With the engine at idle, press on the plunger. When it fully retracts, unplug it. Idle should drop to about 450 RPM (may stall). Now adjust the gap from the plunger to the throttle lever to .060. Plug it back in and your good to go. May have to give it a few drive cycles to "relearn".

codewize
08-08-07, 11:52 AM
That sounds right. Maybe I was thinking of timing being a pain?



After you replace it, it needs to be adjusted. With the engine at idle, press on the plunger. When it fully retracts, unplug it. Idle should drop to about 450 RPM (may stall). Now adjust the gap from the plunger to the throttle lever to .060. Plug it back in and your good to go. May have to give it a few drive cycles to "relearn".

Ranger
08-08-07, 05:36 PM
You might be thinking of the "idle learn" proceedure. My understanding is leave it alone and it will learn on it's own.