Page 1 of 4 1 2 3 ... LastLast
Results 1 to 10 of 36

Thread: Acceleration Issue

  1. #1
    Member
    Join Date:  May 2015

    Location:  Reisterstown, MD

    Posts:    94

    My VIN:    2412

    Club(s):   (DMA)

    Acceleration Issue

    I have an 81 Automatic and have recently noticed an issue during acceleration from a stop. If I give it a good amount of gas it'll lose power, regain and lose power again. About 3 times before it is ok. So it bucks a little. If I slowly accelerate from a stop it's ok. If I am already moving, say 5mph, and accelerate hard it's ok. Once it's moving it runs great. Just when I hard accelerate from a stop. Any ideas? Thanks!

  2. #2
    Senior Member DMC-81's Avatar
    Join Date:  Apr 2014

    Location:  Florida

    Posts:    1,761

    My VIN:    <2000

    Club(s):   (DCF)

    Hi. I wonder if the plunger in the fuel distributor is sticking a little, or perhaps an ignition wire is loose?
    Dana

    1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
    Restored as "mostly correct, but with flaws corrected". Pictures and comments of my restoration are in the albums section on my profile.
    2006 Dodge Magnum R/T (D/D)
    2010 Camaro SS (Transformers Edition)

  3. #3
    Not really banned Michael's Avatar
    Join Date:  May 2011

    Posts:    3,401

    A few things come to mind,
    Fuel filter
    Vacuum leak at or to the advance solenoid , or the solenoid itself
    starving fuel pump, maybe due to the pickup hose collapsing at higher loads or a partially cogged pickup screen
    Vacuum leak at the air side causing a rich condition under load or a dirty air filter.

  4. #4
    Senior Member
    Join Date:  Jun 2011

    Posts:    4,286

    My VIN:    3937

    That sounds to me like either the shift computer on your car is acting up or your auto trans fluid filter is plugged.

    Has your shift computer ever been rebuilt? Or inspected recently to see if any of the wires have gotten melted laying too close to the exhaust piping?

    When was the last time you changed the transmission filter? Or fluid? The ATF filters Michael helped reproduce are a good product.


    Sept. 81, auto, black interior

  5. #5
    Member
    Join Date:  May 2015

    Location:  Reisterstown, MD

    Posts:    94

    My VIN:    2412

    Club(s):   (DMA)

    I just replaced all the vacuum hoses yesterday. It was doing it before and still is. So hopefully not a leak. I replaced the air filter in the last couple of weeks. I have a fuel filter on the shelf waiting to be put on.

    I've had the car 3 years and haven't done the transmission fluid or filter. They are both on the top of my to do list. I don't know if my shift computer has ever been rebuilt.

  6. #6
    Not really banned Michael's Avatar
    Join Date:  May 2011

    Posts:    3,401

    Quote Originally Posted by SShaw View Post
    I just replaced all the vacuum hoses yesterday. It was doing it before and still is. So hopefully not a leak. I replaced the air filter in the last couple of weeks. I have a fuel filter on the shelf waiting to be put on.

    I've had the car 3 years and haven't done the transmission fluid or filter. They are both on the top of my to do list. I don't know if my shift computer has ever been rebuilt.
    So is the transmission slipping or is the engine not making power?

  7. #7
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

    Posts:    6,734

    My VIN:    10757

    Club(s):   (DMA)

    You must determine if it is an engine problem or a transmission problem. One way to do that is to hook up a light box and verify the shift computer is selecting the appropriate gear for the speed and throttle position. My guess is you are not getting 1st gear all the time so you would not get much acceleration. If the problem seems to improve as the motor warms up, it sounds like the shift computer is not working right when cold but gets better as it warms up. It can also be the motor, some systems function to warm the motor up faster and when they don't work or work right the motor won't feel right until it is fully warmed up. Verify the transmission is actually being commanded into 1st gear at a standing start when you notice the lack of acceleration.
    David Teitelbaum

  8. #8
    Member
    Join Date:  May 2015

    Location:  Reisterstown, MD

    Posts:    94

    My VIN:    2412

    Club(s):   (DMA)

    Quote Originally Posted by Michael View Post
    So is the transmission slipping or is the engine not making power?
    I believe the engine is not making power. But I could be wrong.

  9. #9
    Member
    Join Date:  May 2015

    Location:  Reisterstown, MD

    Posts:    94

    My VIN:    2412

    Club(s):   (DMA)

    Quote Originally Posted by David T View Post
    You must determine if it is an engine problem or a transmission problem. One way to do that is to hook up a light box and verify the shift computer is selecting the appropriate gear for the speed and throttle position. My guess is you are not getting 1st gear all the time so you would not get much acceleration. If the problem seems to improve as the motor warms up, it sounds like the shift computer is not working right when cold but gets better as it warms up. It can also be the motor, some systems function to warm the motor up faster and when they don't work or work right the motor won't feel right until it is fully warmed up. Verify the transmission is actually being commanded into 1st gear at a standing start when you notice the lack of acceleration.
    This is helpful, thanks. Is there place that has information on using a light box? I'm not familiar with that.

  10. #10
    Senior Member
    Join Date:  Jun 2011

    Posts:    4,286

    My VIN:    3937

    Quote Originally Posted by SShaw View Post
    I believe the engine is not making power. But I could be wrong.
    When you have this loss of power event upon taking off from a stand still, what do the engine RPMs do?

    Meaning, when you give it gas to get going, do the RPMs rev high and yet you aren't getting anywhere yet? Or do they stay pretty low even though your foot is pressing on the gas and the car should be picking up speed?

    I have had experiences on my own car like this. It was two different things though. The plugged trans filter was starving the transmission of fluid and so even though I was giving it lots of gas, it just had no oomph and wouldn't go anywhere. The RPMs went way up in this case. I would shut the car off (which I think would let the plugged filter relax momentarily and allow some fluid by) and then when I turned it on again, I got going for at least another few blocks. I changed the filter and this never happened again.

    Years before that though, and before I did any work on the shift computer, it was changing gears erratically. I later realized one of the governor leads was melted after laying on top of the exhaust crossover pipe. A test you can do to see if the computer is at fault or not, is to pull the fuse for the shift computer and see how it behaves. The default gear when there is no electrical power to the shift computer is supposed to be 3rd gear. What it feels like when you only have the 3rd and final gear in a DeLorean, is that the car will have no power leaving from a stand still. The car will eventually be okay once you creep up to highway speeds, but will feel like there is next to no power while driving at low speeds in that 3rd gear. Don't drive it like this any longer than you need to to confirm where there problem is. Good troubleshooting test though and easy to do.


    Sept. 81, auto, black interior

Page 1 of 4 1 2 3 ... 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
  •