Page 4 of 5 FirstFirst ... 2345 LastLast
Results 31 to 40 of 41

Thread: What spark plugs for 0.9l Turbo Smart ForFour

  1. #31
    Join Date
    Apr 2009
    Location
    Ecosse
    Posts
    3,803
    Count in from drivers side. Cyl # 3 is adjacent to gearbox.
    Swap coils before worrying about compression. It'll take moments to do and check inlet manifold for temp variations if cyl #3 is still missing.

  2. #32
    Join Date
    Oct 2008
    Location
    Belfast
    Posts
    21
    Swapped ignition coils already along side spark plugs.

    Will check inlet manifold again once its cooled down

  3. #33
    Join Date
    Apr 2009
    Location
    Ecosse
    Posts
    3,803
    Quote Originally Posted by adam1942 View Post
    Swapped ignition coils already along side spark plugs.
    I remembered later you kinda had that covered.

    Quote Originally Posted by adam1942 View Post
    Will check inlet manifold again once its cooled down
    If there is a sticky inlet valve on cyl#3 then the air being blown back past it should heat up that branch of the manifold - it did when mine first started on two cylinders after its rebuild. Alternatively, go straight to compression test. A burned valve (exhaust in my case) reduces compression pressure to level you could probably detect just by blocking the plug hole (thumb when plug holes were less recessed!) and if your compression is so low as to stop the cylinder firing, that as an adhoc test would give some indication of engine condition unless you have a compression tester to hand.
    That you've pegged the misfire to a particular cylinder pretty much rules out shared components eg cam and crank position sensors. Anything in its recent history as a pointer to internal damage? Left sitting, overheated, etc, etc?

  4. #34
    Join Date
    Apr 2009
    Location
    Ecosse
    Posts
    3,803
    Quote Originally Posted by adam1942 View Post
    Will check inlet manifold again once its cooled down
    When you do that, remove the oil filler cap and see if there's any sign of pressure getting past the piston and rings into the crankcase. I think the problem is in the head but a cracked piston could lose compression. Head removal a near certainty now - but before that, if a sticking valve is still suspected, possible it failing to fully seat may be visible with the cam cover off and the engine turned over by hand.

  5. #35
    Join Date
    Apr 2009
    Location
    Ecosse
    Posts
    3,803
    Headgasket could be culprit - if compression found to be low. Hard to spot from the outside though unless leaking to water or oil gallery.

  6. #36
    Join Date
    Nov 2007
    Location
    BANCHORY
    Posts
    3,408
    No 1 is normally at timing chain/ belt end but on French engines they often count from flywheel end.
    Drives a Smart Cdi - 65 to 85 MPG

  7. #37
    Join Date
    Oct 2008
    Location
    Belfast
    Posts
    21
    Right so branch inlet didn't heat up. No pressure negative or positive coming out of the oil filler cap.

    The only thing thats changed is it had a load of fuel from a local station before about 50 miles ago. We have used this station before.

    I decided I'd take it for a drive to see how its actually performing as if it was going to be majorly damaged it was already half way there.

    This is only happening when idling (warm and cold). Whilst accelerating its 100%.

    Just thinking one thing we've noticed is stop-start has maybe worked 4 or 5 times (even when driving for over 30 minutes). I'm starting to suspect the battery potentially??

    I also filled the car with 250ml of NF Octane booster and drove to the nearest station with super and filled it up (maximum of 97ron here and NF is used by the local Subaru lads on track day as its very good).
    Last edited by adam1942; 08-08-2018 at 07:15 PM.

  8. #38
    Join Date
    Oct 2008
    Location
    Belfast
    Posts
    21
    So now the car seems to drive but just idles poorly I'm going to call round to a local Merc specialist and see if he can scan it - before I didn't want to risk it.

  9. #39
    Join Date
    Apr 2009
    Location
    Ecosse
    Posts
    3,803
    Quote Originally Posted by adam1942 View Post
    So now the car seems to drive but just idles poorly I'm going to call round to a local Merc specialist and see if he can scan it - before I didn't want to risk it.
    That seems like a good idea, just in case there is a problem with a sensor.
    Still on the theme of low compression, a couple of things. If it is cranked with say, fuel pump disabled, does the cranking speed seem even ie, it doesn't slow slightly for two cylinders' compression but not a third? Hard to detect but a sign if there.
    Pressure leakage is very much related to time available for it to occur. At idle speed, plenty time - driving normally, less so.
    Keep us posted.

  10. #40
    Join Date
    Jan 2011
    Location
    uk
    Posts
    920
    I'm starting to suspect the battery potentially??
    Possibility, easy enough to eliminate....
    Check the ‘engine off’ voltage.
    Force it further under and stick the headlights on during idling
    You're so money supermarket and you don't even know it!

Posting Permissions

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