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1988 Eldorado
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6 Posts
Discussion Starter #1
I inherited a low-mileage Eldorado from my mom in 2007. Right now it has 85K miles on the odometer, 20K of which are mine. Over the last
3 years, every once in a while the car will speed up on its own. The acceleration is sudden and extreme -- as if you floored the accelerator.
I have witnesses to the fact that I did NOT hit the accelerator instead of the brake. It's happened five times. Once from a stop, three while
driving on the freeway at 65-70 mph, and once driving up a mountain road at perhaps 45 mph.

A possibly-related recent symptom -- driving at a constant speed on a level road, the car will occasionally proceed at the speed
I was going when I take my foot off the gas. Normal operation is a slowdown of perhaps 1 mph every 1 or 2 seconds -- which I formerly
attributed to excellent rolling resistance :-(

A trusted independent GM specialist replaced all the throttle-related hardware and finally said that it was probably the computer dropping
out and resetting itself to maximum throttle and that there was no guarantee that replacing the computer would make any difference.

No codes show up.

The local Cadillac dealer just wanted $250 to "diagnose" the problem. I have reason to not trust the local Cadillac dealers.

Is this acceleration problem a known factory defect? If not, what might be causing it?

Is there a simple way to defeat the idle speed control?
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,286 Posts
I inherited a low-mileage Eldorado from my mom in 2007. Right now it has 85K miles on the odometer, 20K of which are mine. Over the last
3 years, every once in a while the car will speed up on its own. The acceleration is sudden and extreme -- as if you floored the accelerator.
I have witnesses to the fact that I did NOT hit the accelerator instead of the brake. It's happened five times. Once from a stop, three while
driving on the freeway at 65-70 mph, and once driving up a mountain road at perhaps 45 mph.

A possibly-related recent symptom -- driving at a constant speed on a level road, the car will occasionally proceed at the speed
I was going when I take my foot off the gas. Normal operation is a slowdown of perhaps 1 mph every 1 or 2 seconds -- which I formerly
attributed to excellent rolling resistance :-(

A trusted independent GM specialist replaced all the throttle-related hardware and finally said that it was probably the computer dropping
out and resetting itself to maximum throttle and that there was no guarantee that replacing the computer would make any difference.

No codes show up.

The local Cadillac dealer just wanted $250 to "diagnose" the problem. I have reason to not trust the local Cadillac dealers.

Is this acceleration problem a known factory defect? If not, what might be causing it?

Is there a simple way to defeat the idle speed control?
===============================
Is this acceleration problem a known factory defect?
NO -
a readily known problem -
YES -

If not, what might be causing it?
defective ISC - Idle Speed Control motor -

Is there a simple way to defeat the idle speed control?
YES - just unplug the ISC motor -

of course the engine will probably stall at every stop -

just replace the ISC -
and be sure to follow the set-up instructions -
 

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Cadillac 95 STS, 02 SLS
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13,792 Posts
I remember , back in the mid to late eighties, ta Cadillac was one of the brands that was cited as having problems with "spontaneous acceleration." I was especially aware of the problem as I had a 1984 Audi 5000 S Avant that had the problem. After much so called investigation about the problem on Audi 5000's, the verd9ct was that the accidents caused by spontaneous acceleration were caused by driver error and not an electrical (computer), mechanical, or engineering flaw.

In my own case I experienced spontaneous acceleration on four occasions. The engine, while in "Drive" accelerated to 2500 RPM while at a standstill, my foot was on the brake pedal and the brakes held I could shut the motor off. Audi replaced the ICU and I didn't experience this very dangerous malfunction again. I can tell you for sure that in my case the spontaneous acceleration was not caused by "driver error," but by a faulty component.

At the time Cadillac Sevilles were being reported to have had the same malfunction, with injuries and a death reported, but this info was hushed up and completely overshadowed by the news in the press an=bout the problem with Audis.
 

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Registered
1988 Eldorado
Joined
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6 Posts
Discussion Starter #4
===============================
Is this acceleration problem a known factory defect?
NO -
a readily known problem -
YES -

If not, what might be causing it?
defective ISC - Idle Speed Control motor -

Is there a simple way to defeat the idle speed control?
YES - just unplug the ISC motor -

of course the engine will probably stall at every stop -

just replace the ISC -
and be sure to follow the set-up instructions -
Does this account for the involuntary acceleration as well as the defective idle?
 

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Registered
1988 Eldorado
Joined
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6 Posts
Discussion Starter #6
===============================
Is this acceleration problem a known factory defect?
NO -
a readily known problem -
YES -

If not, what might be causing it?
defective ISC - Idle Speed Control motor -

Is there a simple way to defeat the idle speed control?
YES - just unplug the ISC motor -

of course the engine will probably stall at every stop -

just replace the ISC -
and be sure to follow the set-up instructions -
Does this account for the involuntary acceleration as well as the defective idle?

----------

Thanks! It's so nice when problems have a simple solution.

Now I have to wonder why The Guy didn't think of that. I've only told him about the acceleration problem, not the idle weirdness; could the acceleration problem by itself have indicated the idle control motor defect?
 

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Registered
1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,737 Posts
You say idle related hardware but he didn't replace the ISC?? If the ISC looses reference voltage, it might fully extend but that would only affect curb idle in gear or very slight part throttle. Once off idle, the ISC is not controlled by anything. Its waiting for the throttle arm to touch it again. Once it touches, a circuit is complete and the ISC will retract a measured amount depending on engine load at that time. An ISC can not physically depress the throttle at 65 MPH, A cruise control servo can. I would remove the cruise control linkage to the throttle body 1st. It also could be the cruise switch within the lever. That system can be monitored thru on board diagnostics with regard to set, resume and acell. functions. The turn signal lever was modified about that time with a raised section to prevent "resume" from engaging when the turn signals were used at any speed above 30 MPH. .
 

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1988 Eldorado
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6 Posts
Discussion Starter #8
I dug out my receipts...

Feb 2011 Replaced the idle speed actuator (idle air control valve D6576 due to accelerating on its own.
Mar 2012 Replaced the throttle position connector HP4460, Throttle position snsr/throttle position sensor TH38, throttle spring kit (fast idle)
Oct 2012 Rebuilt smog pump 32-428, serpentine belt. Disconnect cruise control and inspect powertrain computer for internal failure (tap test). Replace broken engine mount.

The runaway happened at least once since then.

The cruise control stopped working before I got the car in 2007, and I wouldn't have used it anyway; I hate the damn things. The Guy disconnected the CC after the second episode. So the idle stuff isn't related to the runaway throttle?

More details about the runaways: The five episodes I mentioned wouldn't stop until I turned off the engine. Brake hard, pull to the side, switch off the engine, start breathing again. Engine perfectly normal after that.

The first episode actually consisted of three episodes: one from a dead stop and then two more within 50 miles both at freeway speeds. Others were one-shots.

This week, along with the idle problems, there MAY have been some slight accelerations which stopped immediately on braking. Very different from the original ones, such that I'm not even positively sure they happened -- I'm just getting sensitized to the slightest weirdness.

As you might have guessed, the car has sentimental value or I wouldn't put up with it trying to kill me... It seems wrong to junk a car with only 85,000 miles. It uses no oil and has no other problems, other than cosmetic and plastic.
 

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Current 2014 red CTS Vsport/ Black Raven 2013 3.6 ATS4 gone
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3,513 Posts
I had somewhat of a problem like this with a BMW. I couldn't fix it nor could BMW saying nothing was logged or seems to be wrong with it. I talked to this thing like it was a second wife. Telling it was ok patting it on the dash. I worked on it in the driveway weekend after weekend. Something always came up and didn't make sense. Ultimately I had to get rid of it. I didn't need a second wife nor did I want it to kill me and my family. I saw it 2 weeks ago and feel for the guy who has it. I wanted to stop him and talk but it didn't work out that way. This sounds really dangerous to me. Good luck I hope you get it fixed.
 

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Registered
1988 Eldorado
Joined
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6 Posts
Discussion Starter #10
A friend's kid is a BMW mechanic. The friend gets BMWs at a discount, but he says he'd never buy one unless his son could fix it. The Caddy has been the most expensive car I've ever owned, largely because I used to do my own repairs. It's been a long time since I could name just about any part on a car :-(
 

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Registered
1988 Eldorado
Joined
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6 Posts
Discussion Starter #11
I may have made this reply in a way that didn't actually post...



I dug out my receipts...

Feb 2011 Replaced the idle speed actuator (idle air control valve D6576 due to accelerating on its own.
Mar 2012 Replaced the throttle position connector HP4460, Throttle position snsr/throttle position sensor TH38, throttle spring kit (fast idle)
Oct 2012 Rebuilt smog pump 32-428, serpentine belt. Disconnect cruise control and inspect powertrain computer for internal failure (tap test). Replace broken engine mount.

The runaway happened at least once since then.

The cruise control stopped working before I got the car in 2007, and I wouldn't have used it anyway; I hate the damn things. The Guy disconnected the CC after the second episode. So the idle stuff isn't related to the runaway throttle?

More details about the runaways: The five episodes I mentioned wouldn't stop until I turned off the engine. Brake hard, pull to the side, switch off the engine, start breathing again. Engine perfectly normal after that.

The first episode actually consisted of three episodes: one from a dead stop and then two more within 50 miles both at freeway speeds. Others were one-shots.

This week, along with the idle problems, there MAY have been some slight accelerations which stopped immediately on braking. Very different from the original ones, such that I'm not even positively sure they happened -- I'm just getting sensitized to the slightest weirdness.

As you might have guessed, the car has sentimental value or I wouldn't put up with it trying to kill me... It seems wrong to junk a car with only 85,000 miles. It uses no oil and has no other problems, other than cosmetic and plastic.
 
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