Spark plug diagnosis
  • Register
  • Help
Results 1 to 3 of 3
  1. #1
    Fellow Frogger!
    Join Date
    Nov 2010
    Location
    Brisbane
    Posts
    115

    Default Spark plug diagnosis

    I pulled these out of my 405 the today. for a few months now the engine was running pretty rough, down on power and sounding like it was missing.

    So going by the pictures, it llooks like maybe worn valve guides for cylinders 1 and 3, but what the hell's wrong with cylinder 4? Is this a blown valve or ring? Or what? cylinder 3 looks more or less okay on the tip, though the upper half is black with oil. I noticed this plug was very loose in the well about a month ago, and I tightened it to finger tight but there was no improvement to the running of the motor until I put the new plugs in today.

    Advertisement


    The new plugs are are working a treat and the motor is no longer missing and the power is back. I haven't driven the car enough to have a look at how the new plugs are faring.

    I would appreciate any ideas anyone has about the state of these plugs.


    Peugeot 405 used spark plugs by max_wedge, on Flickr
    1992 405 SRI 1.9lt White Series I
    2001 206 GTi 2.0lt Diablo Red

  2. #2
    1000+ Posts HONG KONG PUGGY's Avatar
    Join Date
    Nov 2002
    Location
    Yarrabilba, Queensland
    Posts
    2,758

    Default

    How old are they??

    Max, what's the inside of the plug chamber look like for the rusty plug? Did it suffer water ingress at some time? Is the plug still fully attached between the metal/ceramic section? Looks like it could have been fractured when last tightened.
    NGK plug diagnosis from their website.

    http://www.ngkspark.com.au/sparkplug_tech.php#

    The 405 is a coil pack engine isn't it? How's the coil pack's health? Is it fine at all temps and speeds?
    2016 Renault Sport Clio Cup EDC 200



    Previous

    2001 Rx-4 Privilege
    R17TL, 1973
    R20TS x 3
    R18 GTS wagon x 2
    R10





    "When you hit the tree between the headlights thats understeer. Oversteer is when you hit the tree between the Tail Lights" - Wayne Bell

  3. #3
    Fellow Frogger!
    Join Date
    Nov 2010
    Location
    Brisbane
    Posts
    115

    Default

    Thanks for the reply.

    Spark plugs are pretty old, last plug change was about 7 years ago. Last time I checked the plugs was about three years ago, and not being worn at all and having a light tan colour, I didn't replace them. The engine has run fine since then, also with good fuel economy (until a few months ago when it started running rough).

    The plug is solid ie: No break in the ceramic or other obvious split. The rust isn't on the thread or tip. However I haven't had the cylinder head off so I'm not sure of the condition inside.

    The rust may be a hang over from a creak crossing incident: That spark plug recepticle did have water ingress at a creek crossing. The engine was misfiring but I drove for a couple of miles just thinking there was residual water that would dry out but when it didn't I stopped and checked the engine, and noticed a pool of water in that plug's hole. I soaked it up with a paper towel until it was more or less dry, though there may have been a few mmm still in there. The engine ran normal afterwards. (kicked myself for not having WD-40 in the car!)

    That incident was about 3 years ago.

    Coil pack was replaced about 2 years ago. Engine starts first time everytime (even with the rough running). Ignition system seems in good condition.
    1992 405 SRI 1.9lt White Series I
    2001 206 GTi 2.0lt Diablo Red

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

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