: God ! please help me before my caddy kills me..

02-24-04, 02:31 PM
here we go again.....
upon start up of my 93 sts with approx 80,000 miles (140k km), the car will sit for 60 secs or so, (depending on the weather) and then the rpms will climb slowly to over 2200 , and then just sit there and idle excessively high. Even tho that northstar sounds sweet revving, its sucks standing outside the car , and hearing it purring away, for no reason. Anyways......so ill press the brake (fairly hard) and the rpms fall to a regular idle and then i can shift the car into drive or N or R or whatever.....but if i fail to do so, the tranny clunks from being shifted at 2200 rpm CLUNK!!! Light pressing of the brake does nothing. must be pressed firmly to make the rpms fall to be able to shift.

Now, i head out on the road, and the cars idle will not drop unless im being very assertive with the brake. What i mean is, with my foot off the accelerator, the cars rpm climbs slowly, and it gains speed at an alarming rate. BY ITSELF!!! its actually sorta scary, even when the brake is pressed, the car still wants to go forward...sometimes coming to a slow stop is almost impossible, the wheel swant to keep going, the tranny wants to keep pushing, but the brakes are full on. and about 5-10 mins after it started doing this, the SERVICE ENGINE SOON light came on......then i $hit my pants.

please please please...any help is appreciated.....

also...big thank you to logan and bobynski, who helped me out last time with my starter enable relay......much respect. I need your expertise again, guys.:confused: :crying2: :madtalkin me and caddy have a love hate relationship.


02-24-04, 02:44 PM
I had it happen twice, i shut off the engine, tromped the accelerator a couple of times, turned off the cruse control, restarted, watch the rpm's drop down to 750 before shifting. Has not recurred in 4 months.

02-24-04, 03:09 PM
I had it happen twice, i shut off the engine, tromped the accelerator a couple of times, turned off the cruse control, restarted, watch the rpm's drop down to 750 before shifting. Has not recurred in 4 months.
ok..i just went ouit to the car...pumped the brakes 2 x...then shut off cruise.....then i restarted.....look out!!!!!!!!! the car shoots up to 3500 rpm , by itself, and stays there.....im thinkin i just gave it a huge shot of gas, and it has almost flooded itself.....so it needs to burn off the gas....but this also leads me to believe that in have carbon build up .....and maybe a a little bit of injector cleaner will help.....has anyone had a similar problem?:bonkers:

thanx anyways 97deville

02-24-04, 03:31 PM
sorry, in the last post, i meant that i pumped the accelerator a couple times, not the brake, .........now i cant start the car with out maintaining an idle of 3500!!!!!!!!!!! how can i release the gas pressure?..... open up the intake i am assuming.....am i right on this?

anyways....what the frig?!....ignition then 3500 rpm steady:hmm: ....ouch.

02-24-04, 03:52 PM
Vacuum leak or torn up ISC motor.


02-24-04, 04:00 PM
Check the linkage, see if the throtle is being held up by something (cruse or the idle speed control )

02-24-04, 04:04 PM
Could be, but first I would check the throttle linkage and make sure it is not hanging up. Pull the rubber intake duct. Then you will be able see the throttle body butterfly plate, throttle cam and cable. Be sure the butterfly is seating all the way. Best way would be to grab the cam with your hand and try to close it. Then open and close. If it is not closing tight find out why. Probably will need to clean. I use CRC throttle body cleaner. Watch carefully as it does not need to be open much to make the motor race. You can also see the ISC motor down low below the throttle cam. It pushes on the same linkage from down below. Check to see if it is holding the linkage open. If so you may be able to disconnect it until you get a replacment.

02-24-04, 04:07 PM
97Deville beat me to it.........post wsn't there when I posted. But yes try that first.

02-24-04, 04:19 PM
ok, the update is, i just went out and took off the air box , and exposed the butterfly, cleaned it up, checked the linkage, seems to be ok..ill pull it the opposite way , and there seems to be no friction, nothing in the way of the throttle cable....

man...once again....caddy's got me stumped

what is this isc motor?:hmm:

02-24-04, 04:22 PM
what is this isc motor?:hmm:[/QUOTE]
idle speed control

02-24-04, 04:44 PM
where is the isc motor to be exact, and how do i go about testing it to see if it is shot....im not really familiar with an isc.....

also, i just called the CADY dealership and he said same things , linkage,throttle body stickin, but he also said, fuel pump. Does this seem feasible? Or is he jus throwin anything in?

i cant evn put it in gear, to move it into the garage....and theres ice everywhere....prolly no luck pushin it....

02-24-04, 07:46 PM
was the isc....thanx to all.

02-24-04, 09:05 PM
After cleanning the TB valve (inside) and the bore, you need to disconnect the negative battery terminal for 30 sec, so the computer will learn to adjust the idle speed.

02-24-04, 09:48 PM
As mentioned it sounds like a vacuum leak.

Listen for air hissing under the hood after starting, hose pulled loose?

Check the screws all around the intake cover, snug them up do not over tighten them.


02-24-04, 10:07 PM
Switzer said that when he presses the brake firmly, the rpms go down. I don't think this is a mechanical problem. You can't properly seat a butterfly by pressing the brake. It's got to be the motor or relay or electrical device that controls the idle.

02-24-04, 10:19 PM
was the isc....thanx to all.
I guess I was late, but I was right! ;)

02-25-04, 01:45 AM
what is this isc motor?:hmm:

Switzer........just to answer your question, Idle Speed Control

Glad you found it.

STS 310
02-26-04, 05:25 PM
Vacuum leak or torn up ISC motor.

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Logan ive been watching your posts since i began as a member in 12-03. Let me just say that i really appreciate your input and the way you have helped so many. You truly are a "wiz" and its great that you are part of this forum.

Thanks Again