94 SLS feels like its going to stall when at stoplight
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 13 of 13
Northstar Engines and System Technical Discussion Discussion, 94 SLS feels like its going to stall when at stoplight in Cadillac Engine Technical Discussion; Hi, Have a bizzar issue. 94 Seville SLS. 65,000 miles. Runs great and idles nice. Problem arises after the car ...
  1. #1
    chester_007 is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Mar 2011
    Posts
    20

    94 SLS feels like its going to stall when at stoplight

    Hi,

    Have a bizzar issue. 94 Seville SLS. 65,000 miles. Runs great and idles nice. Problem arises after the car warms up some. I come to a light and stop. For about 5-10 seconds car idles fine, then it acts like its going to stall, then suddenly surges and levels back out. Rinse and repeat... until it will finally stall. Does not do it out of gear. Does it in all gears forward and reverse. I can simply put it in gear and sit there. Will idle fine then drop and surge back up. I did change the lower crank position sensor because the old one was leaking. It ran fine prior. Could it be the new crank sensor? Or a coincidence? I would have thought that if it was the crank sensor it would stumble and sputter while driving but it runs like a top otherwise..

    Thanks!

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    CadillacLuke24's Avatar
    CadillacLuke24 is offline Cadillac Owners Connoisseur
    Automobile(s): Alexandra - 96 SDV
    Join Date
    Jul 2010
    Location
    Middle of Nowhere
    Age
    23
    Posts
    4,856

    Re: 94 Seville SLS feels like its going to stall when stopped at stoplight, sometime

    Is the check engine light on?

    Pull your diagnostic codes. Those will help fill us in.

    How old are the plugs and wires?

  4. #3
    chester_007 is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Mar 2011
    Posts
    20
    Quote Originally Posted by CadillacLuke24 View Post
    Is the check engine light on?

    Pull your diagnostic codes. Those will help fill us in.

    How old are the plugs and wires?
    No codes or check engine light

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,821

    Re: 94 Seville SLS feels like its going to stall when stopped at stoplight, sometime

    Sounds a lot like a vacuum leak.

  6. #5
    stoveguyy is offline Cadillac Owners Connoisseur
    Automobile(s): 03 STS
    Join Date
    Aug 2007
    Location
    mpls mn
    Posts
    2,494
    I had a sticky egr that caused funky idle for a long time. I could make it stick open real easy. But than I always got egr code too. Different egr and all is well.

  7. #6
    chester_007 is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Mar 2011
    Posts
    20

    Re: 94 Seville SLS feels like its going to stall when stopped at stoplight, sometime

    Quote Originally Posted by CadillacLuke24 View Post
    Is the check engine light on?

    Pull your diagnostic codes. Those will help fill us in.

    How old are the plugs and wires?
    No codes other then one for the RF suspension sensor.

    Plugs and wires are probably the originals as the air filter was. LOL

    ----------

    Quote Originally Posted by Ranger View Post
    Sounds a lot like a vacuum leak.
    Wouldnt a vacuume leak cause and erratic idle all the time? The car idles fine in park and does in drive when you stop - smooth then all of a sudden it drops then levels out again.

  8. #7
    CadillacLuke24's Avatar
    CadillacLuke24 is offline Cadillac Owners Connoisseur
    Automobile(s): Alexandra - 96 SDV
    Join Date
    Jul 2010
    Location
    Middle of Nowhere
    Age
    23
    Posts
    4,856

    Re: 94 SLS feels like its going to stall when at stoplight

    A vacuum leak can cause an erratic idle. Pop the hood, and with the engine running, use a can of tb cleaner to spray the rubber tubing. If the RPMs increase, you've found your leak. Don't remove the beauty cover, as it's actually part of the intake manifold. If you don't find any leaks, I would think the more expensive chore of plugs and wires would be in order. AC-Delco 91-450 plugs and the appropriate wireset.

  9. #8
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,821

    Re: 94 Seville SLS feels like its going to stall when stopped at stoplight, sometime

    Quote Originally Posted by chester_007 View Post

    Wouldnt a vacuume leak cause and erratic idle all the time? The car idles fine in park and does in drive when you stop - smooth then all of a sudden it drops then levels out again.
    Usually yes.

    When was the TB last cleaned?



    I did change the lower crank position sensor because the old one was leaking.
    Change one, change 'em both. That's like only changing 4 spark plugs.

  10. #9
    chester_007 is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Mar 2011
    Posts
    20

    Re: 94 Seville SLS feels like its going to stall when stopped at stoplight, sometime

    Quote Originally Posted by Ranger View Post
    Usually yes.

    When was the TB last cleaned?



    Change one, change 'em both. That's like only changing 4 spark plugs.
    Cleaned the throttle body the other day - no help.

    I have a set of plugs and going to get new wires - just because I like doing that to all the cars I buy so I know what's what but I honestly don't think its the issue.

    I'm personally leaning toward the throttle position motor. The throttle position motor gives the car gas under load to keep the RPM's constant. In park there is no load so the motor would have no work. Driving the car I'm pushing on the gas pedal so same scenario. But, when I come to a stop there is a load on the drivetrain that the throttle position motor has to compensate for right? So say its going bad and it drops the throttle position for a second then reinitializes to proper location. That would explain the sudden drop in RPMs and then the surge of the TPM overcompensating to keep the motor running. I've also noticed gas pedal movement during this time. Yesterday I had my foot on the gas and my left foot on the brake. I felt the gas pedal move when the surge occurs. Didn't dawn on me till yesterday since I'm not a two footed driver...LOL At least that's my theory. I have a spare NS in the garage that I'll pull the TPM off of and swap them to see if there's any difference. I'll let you know how it turns out...

  11. #10
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,821

    Re: 94 SLS feels like its going to stall when at stoplight

    What you are talking about is the ISC (Idle Speed Control) motor. "Throttle position motor" had me thinking you where talking about the TPS (Throttle Position Sensor). Yes it could be a bad ISC motor (or maybe just the closed throttle switch).

  12. #11
    chester_007 is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Mar 2011
    Posts
    20

    Re: 94 SLS feels like its going to stall when at stoplight

    LOL Thanks. That's what I meant... Got a lot on my mind these days..

  13. #12
    chester_007 is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Mar 2011
    Posts
    20

    Re: 94 SLS feels like its going to stall when at stoplight

    Just a quick note that the idle speed control motor took care of the issue.

  14. #13
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,821

    Re: 94 SLS feels like its going to stall when at stoplight

    Thanks for the feedback.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting