rough idle

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 3 of 3
5.0 and 5.7 Discussion, rough idle in Cadillac Engine Discussion; when the car is cold or only slightly warmed up my car barely idles and sometimes even dies. i noticed ...
  1. #1
    89fatb's Avatar
    89fatb is offline Cadillac Owners Fanatic
    Automobile(s): 1989 fleetwood brougham 145k
    Join Date
    Dec 2004
    Oconomowoc, WI

    rough idle

    when the car is cold or only slightly warmed up my car barely idles and sometimes even dies. i noticed that if i cover the carb with my hand it idles beautifully. that leads me to believe its running lean. the question is if it is running lean or if the idle speed is incorrect? is the ilc plunger suppose to be against the throttle lever, cuz its not...btw it does fast idle when i pump the gas when i get in the car, its when i kick it down i have these problems. choke opening too soon?

    thanks guys for all the help i have recieved in the past, i really got to get around to posting a pic of my ride

  2. Remove Advertisements

  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1999 BMW 740 Il. 2005 Jag XK8, 1988 Mercedes Benz 300 SE
    Join Date
    Feb 2003

    Re: rough idle

    These chokes do open quickly by nature, so as to not let the engine run too rich too long (emission rules) I would verify the secondary choke break is adjusted to the proper setting. The service manual speaks to a certain drill bit diameter that is inserted between the carb bowl and the choke blade. If that distance is too great, the choke blade would go vertical too quickly and if it was not great enough the engine would load up. I'm thinking that distance needs to be closed a bit. My other thought is to pump the throttle to set the choke then once running, put in gear and drive away, dont kick it down. Once you apply throttle to drive away the fast idle would drop a bit anyway and it might help the transition from cold engine to warm engine. Also verify the door in the air cleaner snorkle is closed upon cold start. If staying open all the time, it would cause cold running driveabilty stumbles. That flexible hot air tubing to the aircleaner is there to provide hot air to the carb only during cold start, then the door opens in the air cleaner and fresh air is allowed to the carb.

  4. #3
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
    Automobile(s): 94 Fleetwood Brougham
    Join Date
    Aug 2004
    Rockford, IL

    Re: rough idle

    I was thinking the same thing, I have fussed with the initial choke opening on mine as it was a 350 in place of the 307 so mine had to have some slight tweaking. It needs to open to around 0.1" within a couple seconds off cold start (primary vacuum break, aka, choke pull off opens this up right away). The secondary vacuum break is delayed by the ECM to around 30 seconds, depending on temps (we aren't having warm ones right now here!). It starts to pull a little bit more and at that point the choke probably isn't getting warm just yet, maybe, it is in the exhaust stream there. Make sure there is no vacuum leaks on the choke hot air tubes too.

    You set the primary vacuum opening with the phillips screw there on the pass side. Turn it clockwise just a little. See if that helps.

    At fast idle the ILC won't be pushing on the throttle, as the vacuum will be keeping it fully retracted. The fast idle screw is down underneath, pass side on the primary throttle blade shaft. I tweaked mine to be slightly lower than stock to keep it from racing at cold startup.

    I have the FSM for the 85 if you need any procedures or dimensions. For the "Y" 307 it should be the same as 89

  5. Remove Advertisements
    Cadillac Forums

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

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

Please enter a valid email address for yourself.

What Cadillac(s) do you own? (Or type NONE)

Please select your insurance company (Optional)


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.


Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts