: 94 Deville Concours- Idle in Drive Rough



devilleconcours100
12-29-06, 11:23 AM
When I idle the deville in park it runs fine. I changed the battery not too long ago, and had to let it sit in park and idle for 25 minutes while the computers were recalibrated. It ran great. But sometimes when I am out on the road, and come to a stop light, or go through a drive thru, it idles strangely. It idles low then high and I can hear a little knock like noise, but when I go and either accelerate or put the car in park, it ends immediately. I am somewhat lost as to what to do, and I haven't taken the car to the mechanic I use (Warsaw Chevrolet-Oldsmobile), and was hoping that I could wait until my next oil change to do so (usually if I want a minor problem diagnosed, and I came in for an oil change, they do it for free), but if anybody has an idea as to what this is, please let me know. I am working in real estate now, (have finally left auto sales and repairs behind), and have to have a reliable car, (also have a Lincoln Town Car:o and a Mercedes S Class (both were required to join the realtors associatation;) ), so if it quits, I have something to drive, but I enjoy my caddy so much, I like to run it.)
Happy New Year, Dave.

Ranger
12-29-06, 04:42 PM
RPM hunting could be vacuum leak or a failing ISC motor. Knocking may or may not be related and is hard to tell from here. You'll need to do some investigating to narrow it down and isolate it a bit.

dp102288
12-29-06, 08:56 PM
Check to see if there are any diagnostic codes. There is a sticky in the Tech Tips if you are not sure how to do that. Might be some info the car's computer to help.

Never knew there was a car requirement to be a realtor!

caddyman2005
12-29-06, 11:54 PM
The PCM maybe having problems relearning the Idle with a dirty throttle body the clicking or ratacheting noise is probably the isc motor trying to extend past its limits. I would clean the throttle body and relearn the idle.

Robert

94CaddyConcours
01-01-07, 07:47 PM
(also have a Lincoln Town Car:o and a Mercedes S Class (both were required to join the realtors associatation;) )
You got to be kidding me. A Realtors(R) need a MB and LTC. Never heard of it. What region are you from? Also What year is your S class?

devilleconcours100
01-01-07, 08:31 PM
The thing about the benz and town car was a joke an associate told me after I got into real estate. :D . Glad to see it got a response. Anyway, did the Idle relearn, still have the same problem. Checked the diagnostics, and there were no current or past history codes. I assume that to clean the throttle body, it would need to be removed from the car?
Thanks, and God Bless,
Dave.

devilleconcours100
01-01-07, 08:32 PM
Oh, I had a new Throttle Position Sensor and Idle Speed Control Motor put on about 6 months ago.
Thanks, and God Bless,
Dave.

Ranger
01-01-07, 08:39 PM
No need to remove the TB. Just hold the throttle plate open, spray it down with TB cleaner and scrub down the TB bore & throttle plate with a tooth brush & rag til you get all the carbon off of it.

devilleconcours100
01-03-07, 05:01 PM
I just got done cleaning out the TB, per Instructions on Tech Tips Thread. Seemed to be pretty cleaned compared to some, and I did idle relearn again. I'll let you know how it works out.
Thanks, and God Bless,
Dave.

devilleconcours100
01-04-07, 08:57 PM
Well, its still doing its little RPM hunting thing, but its not as bad. Also, I'm averaging 25.7 MPG :). Anyone have some more ideas?
Thanks, and God Bless,
Dave.