MMT Contamination - Rust Coloured Spark Plugs

  1. Welcome to Saabscene – General discussion forum for Saab

    Welcome to Saabscene - a website dedicated to all things Saab.

    You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, Join Saabscene today!
Results 1 to 2 of 2

Thread: MMT Contamination - Rust Coloured Spark Plugs

  1. #1
    Saab Nut
    Join Date
    Aug 2009
    Sunbury on Thames
    Not a lot of people know this.... :-)

    Just finally diagnosed a problem with my wife's Rover 220. Its not well known and took ages to Suss, so here is the news.

    I found the problem after searching on Google and finding a picture of an identical set of Honda plugs which had caused the same problem.

    The symptoms are occasional misfires, jerkiness, mostly when cold and at low revs pulling under load. This gets worse and then includes poor cold starting.

    The plugs looked weird, gapped OK and not corroded at all, but with a uniform rust coloured deposit all over them, I know all the usual symptoms having been bought up on carburetted oil burners. Still nostalgic for that lightbrown 14:1 mix on the twin SUs.

    Turns out the colouration is a deposit left by an Octane improver called Methylcyclopentadienyl manganese tricarbonyl (MMT or MCMT), used by some petrol companies but not others, banned in many US States, just re authorised in Australia, and clearly used by Tesco, my wife's petrol supplier of choice.

    See pics for a better idea. (Yes the No 4 cylinder has the classic Rover T-Series engine head gasket failure ongoing).[email protected]/...57625242012419/

    New plugs totally cured this long running problem. I have not yet tried cleaning the old ones. I suspect with my anti environmental point and squirt between corners and as fast as you can get away with on Motorways "enjoy the HPT while you still can" driving I'm OK with my 9000 Aero, but if you are a gentle caravan towing driver of a regular injection non turbo you may experience this - particularly with a caravan - serves you right :-)

  2. Remove Advertisements

  3. #2
    Ewww, that's nasty. At least with most SAAB's the plugs are cheap enough to be changed yearly.

  4. Remove Advertisements

Similar Threads

  1. Spark plugs
    By xantia31 in forum Saab 9-3 Sport Saloon / Combi(Estate)/TurboX/AWD (2003 - on)/Convertible(2004 - on)
    Replies: 2
    Last Post: 08-09-2009, 05:21 AM
  2. Spark Plugs
    By xantia31 in forum Saab 9-3 Sport Saloon / Combi(Estate)/TurboX/AWD (2003 - on)/Convertible(2004 - on)
    Replies: 1
    Last Post: 07-16-2009, 11:30 AM
  3. Spark plugs
    By jameswarlow in forum Classic Saab 9-5 (1997 - 2009)
    Replies: 11
    Last Post: 06-19-2009, 09:20 AM
  4. Spark Plugs
    By msteers in forum Classic Saab 9-5 (1997 - 2009)
    Replies: 10
    Last Post: 07-04-2007, 04:15 PM
  5. Spark plugs
    By Gary N in forum Saabscene: Performance
    Replies: 6
    Last Post: 10-26-2004, 07:45 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Powered by vBadvanced CMPS v4.1.2