Page 1 of 2 12 LastLast
Results 1 to 10 of 15

Thread: A/F ratio question

  1. #1

    Default A/F ratio question

    Recently I have been having some small issues. While going over the settings and readings, I found that key on/engine off I have an o2 reading... I would think it would be 0 since the engine is off... Do I have an o2 sensor issue?

    Can anyone confirm what their reading is after the o2 goes through the warm up without the engine running?

  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,589

    Default

    With the engine off, there is eventually normal atmosphere in the exhaust system.

    So it would go high oxygen, lean condition, low volts almost zero.

    What readings do you have?

    Gary
    Regards, Gary

  3. #3

    Default

    In getting any where from 19.7 to 39.6

  4. #4
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,589

    Default

    I wouldn't be concerned about A/F ratios like that with engine off.

    How long is the engine shut off for, when you see 19.7:1?

    If still displayed 14:1, I'd be concerned.
    Regards, Gary

  5. #5

    Default

    30 min. 4 hours for the 39.5

  6. #6
    Join Date
    Mar 2016
    Location
    Egg Harbor Township NJ
    Posts
    1

    Default

    You will also note a high A/F ratio over 35:1 (On the MSD) when the engine is reved above 2000 rpm and you release the gas pedal. Fuel will be turn off at the point your release the pedal (Say 3500 Rpm) and turned on agin at 2000 RPM ...this in my case causes a Back fire. This is what I'm Trying to Get MSD to Correct.

    I have an Innovative A/F gauge on my steering colunm which shows this dead spot also. The MSD will show 35:1 lean or fuel off.

    So seeing no A/F reading engine off would be normal after 02 senor heat up.

  7. #7

    Default

    Quote Originally Posted by mrkrichman View Post
    You will also note a high A/F ratio over 35:1 (On the MSD) when the engine is reved above 2000 rpm and you release the gas pedal. Fuel will be turn off at the point your release the pedal (Say 3500 Rpm) and turned on agin at 2000 RPM ...this in my case causes a Back fire. This is what I'm Trying to Get MSD to Correct.

    I have an Innovative A/F gauge on my steering colunm which shows this dead spot also. The MSD will show 35:1 lean or fuel off.

    So seeing no A/F reading engine off would be normal after 02 senor heat up.
    Agreed, my concern is that I do have a reading with the engine off and the o2 warmed up.

    I would have expected to see a 0 reading.

  8. #8
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,589

    Default

    Quote Originally Posted by kyddsply View Post
    30 min. 4 hours for the 39.5
    I wouldn't be concerned with this.

    Is there any other issue, driveability, power etc?
    Regards, Gary

  9. #9

    Default

    Quote Originally Posted by Gaz64 View Post
    I wouldn't be concerned with this.

    Is there any other issue, driveability, power etc?
    I have had a change of exuast tone, almost as if it was running too rich, and a light but consistant popping during acceleration. ALSO a rich condition when coming down to idle. It does correct itself after about 30 sec. to a minute.

  10. #10
    Join Date
    Mar 2016
    Location
    Egg Harbor Township NJ
    Posts
    1

    Default

    Asumming you have done the initail set up and cam selection proces and throttle plate setting for each cam type which im sure you have done then you can elininate that. If you have not done that that I would go back to square on in the manual and follow the throttle plate setting for each cam type.

    Just trying to help out hear and I'm sure you know what your doing, This is just my responce to your problem that you have posted. Others can chime in with something I have missed. I'm not the expert but we have some good guys here including our MSD Techs.

    Hope you nail it down:thumbup:

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us