Misfire Over Bumps | FerrariChat
Buy

Misfire Over Bumps

Discussion in '308/328' started by nullspace, Aug 1, 2014.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. nullspace

    nullspace Karting

    Apr 1, 2014
    92
    #1 nullspace, Aug 1, 2014
    My 308 QV occasionally misfires when I hit a bump. It's infrequent, happening maybe twice on my one hour drive last night. It seems much more likely to happen when the car is hot and when I'm going uphill, but that could be my imagination.

    I've already installed Birdman fuse blocks and replaced all the relays. So the obvious answer would be a loose connection somewhere, but where? I don't know a good way to diagnose the problem without blindly replacing a ton of electrical.

    My suspicion is one of the plug extenders, but it's just a guess. I did notice one of them isn't super tight like the others - should they be completely tight or is a tiny bit of play normal?

    Any other ideas? I appreciate the help.
     
  2. BumpyBrandy

    BumpyBrandy Rookie

    Mar 16, 2024
    2
    Full Name:
    Nope
    #2 BumpyBrandy, Mar 16, 2024
    I have the exact same problem with my 83 308 QV. It also happens when turning hard hard left, but its real bumpy patches like rough road with potholes and literally every bump feels like it corresponds to a misfire, the second bumps stop car drives perfectly. Please advise best advice re electrical possibilities. If I bring it to the dealer with no well founded direction they are gonna try everything under the sun and spend a fortune probably not fixing it. Thanks!
     
  3. Plutonium

    Plutonium Karting

    Jul 29, 2020
    97
    Full Name:
    1980 308 GTSi
    #3 Plutonium, Mar 16, 2024
    This video may help
     
  4. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,951
    Isle of man- uk
    #4 mike32, Mar 16, 2024
    Ok he had a faulty coil but why did it fail just on right handers ? Weird !!
     
  5. BumpyBrandy

    BumpyBrandy Rookie

    Mar 16, 2024
    2
    Full Name:
    Nope
    #5 BumpyBrandy, Mar 17, 2024
    This is VERY helpful. Thank you!
     
  6. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    6,871
    Full Name:
    Mike 996
    #6 mike996, Mar 17, 2024
    Some years ago we had the same symptoms with a vehicle that would cut out on hard left turns - faulty coil. No cutting out on "normal" left turns. Coils can do decidedly odd things...
     
  7. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    6,871
    Full Name:
    Mike 996
    #7 mike996, Mar 17, 2024
    I should have added this to my previous message: Re what to check...

    Secondary wires with old/poor insulation can short/ground on the engine/other metal parts. Such a wire could be sufficiently clear of any metal/other wires to work fine normally but short out if a bump moves it to touch or get too close to other wires/metal parts. Of course, good quality wires in good condition can lay on metal parts/the engine/on top of each other with no problem.

    A quick, shade tree check of the secondary wiring is:

    After dark, open the engine lid and start the car. Once it's running smoothly, spritz water from a spray bottle onto the secondary wires, including the coil to distributer secondary wires. Look for any sparks between the secondary wires or between the wires and any metal. To check for "bump" reaction push the wires around with a stick to see if you can induce sparks. If no sparks, the wires are OK. If the wires are not OK, the resulting light show can be quite impressive. Obviously if you see sparks immediately after starting the engine/before spritzing, there is no need to apply water/move wires. Replace ALL wires if there is any sparking from ANY of them.

    Assuming no sparks, and you haven't already, spritz water onto the distributer(s) . Same deal - any sparks, replace the offending parts. A distributer is not likely to be related to cut-out during a bump but you might as well ensure the entire secondary system is in good shape.

    Of course, if it's a primary wire/component causing the problem, that could be much harder to locate since it's an intermittent problem that occurs during a bump. :(
     

Share This Page