poor gas milage
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 7 of 7
HT4100 4.1, 4.5, 4.9 Discussion, poor gas milage in Cadillac Engine Technical Discussion; hope this is the right place. i have a 95 cadillac sedan deville 4.9l engine,i recently replaced the the engine ...
  1. #1
    cadillaceldorado is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    poor gas milage

    hope this is the right place. i have a 95 cadillac sedan deville 4.9l engine,i recently replaced the the engine with a remanufactured one(3yr unlimited milage),right after installation there was a problem with the nuimber 5 cylinder(oil and antifreeze leaking in) the heads were replaced and the car runs find now.however the gas milage is very poor(new wires,plugs,egr valve,o2 sensors,gas ,oil,air radiator,distributor,rotor,water pump were put in) on expressway i get 20mpg,but just driving around city it drops down to 7.9mpg any ideas to my promblem,the engine has 1200miles. also the idle is some time up and down but it never does it when i'm at the mechanic

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    awadecki is offline Cadillac Owners Enthusiast
    Automobile(s): 76 Eldo (54k), 76 Eldo (52k), 78 Eldo (9k), 85 Deville (43k)
    Join Date
    Jun 2005
    Location
    Michigan
    Posts
    668

    Re: poor gas milage

    Possibly bad FPR, or a leaking injector. If you had a reman engine put in, they simply removed the fuel rail and reinstalled it, so even though your engine is new, your FPR and injectors are old.

    4.9s eat factory injectors. I'd bet one is bad. Do a balance test using the onboad ECM overrides.

  4. #3
    cadillaceldorado is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Re: poor gas milage

    thanks for the info. how do you do the balance test,what is the FPR?,and should i replace all the injectors or will the balance test tell me which one is bad?

  5. #4
    cadillaceldorado is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Re: poor gas milage

    Quote Originally Posted by awadecki View Post
    Possibly bad FPR, or a leaking injector. If you had a reman engine put in, they simply removed the fuel rail and reinstalled it, so even though your engine is new, your FPR and injectors are old.

    4.9s eat factory injectors. I'd bet one is bad. Do a balance test using the onboad ECM overrides.
    love the car but not a mechanic.thanks for the info.what is the FPR (fuel pressure rail?),how do i do balance test? injectors are $90.00 ea. do i have to replace all?

  6. #5
    awadecki is offline Cadillac Owners Enthusiast
    Automobile(s): 76 Eldo (54k), 76 Eldo (52k), 78 Eldo (9k), 85 Deville (43k)
    Join Date
    Jun 2005
    Location
    Michigan
    Posts
    668

    Re: poor gas milage

    FPR=fuel pressure regulator. First, pull the vacuum hose off of it (it's a black, round thing next to the throttle body, attached to the fuel rail) and spray in the nipple with WD-40, lots of WD-40. Then, reconnect the vacuum hose and blip the throttle about 15 times and drive the car around. See if that helps.

    You don't need to replace all the injectors. Do a search here on how to perform a balance test--I'm too tired to type it all out.

    Basically, you hit a couple of buttons on the dash, and you can cycle through each cylinder and shut off an injector. While doing this, you measure the RPM drop on the cylinder. If the RPM drop on one cylinder is a lot less than on the others, you have a leaking injector.

  7. #6
    cadillaceldorado is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Dec 2006
    Posts
    14

    Re: poor gas milage

    thank your the best will let you know how it turned out

  8. #7
    NickySantoro is offline Cadillac Owners Fanatic
    Automobile(s): 1993 Eldo 4.9 66K miles
    Join Date
    Nov 2005
    Location
    Nazi Jerky, libtard central
    Posts
    368

    Re: poor gas milage

    In light of the two symptoms you relate, you might wish to check the timing to see if it is retarded as well as cleaning the throttle body and blades.

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