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Any Car Mechanics In Here?

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  • Any Car Mechanics In Here?

    Piston rings, head gasket or something else? -

    one cylinder is fouling a plug, looks like oil... there's little blowby noteable when the oil filler cap is removed so I'm not thinking it's the rings to be honest. There is a degree of pressure in the coolant system and some traces (blobs) of oily gunk plus the coolant has needed topping up a few times lately.

    Clean plug and the car starts and idles fine, but then after a few minutes idling/driving it fouls the plug again and drops to 3 cylinders... grrrr... no power loss other than when this happens, it did this a few times then ran fine for a while, now it's doing it constantly.

    Haven't got a compression tester (yet) but will be checking that as a matter of course, but given the lack of blowby I can't see the rings being shot to the point where a plug could foul that quick...

    Thoughts? It's a 25yr old Audi based 2.0 litre injection engine btw.

  • #2
    Whats your fuel consumption like - has it increased at all ?

    When did it last have a service ?

    Whats the appearance of the oil like - is it like black treacle looking or just mid brown and smooth ?

    Is the fuel injector cutting in at the right point ?

    I am wondering if it could be your points to be honest, but until you come back with something a bit more definitive then I can't give you a total diagnostic lowdown.


    • #3
      It's definately oil on the spark plug, i ruled out the injector last night with a clean plug in for all of 2 minutes before it was fouled...

      sump oil is dark, smells fine though (no petrol smell to it, which i'd expect surely if the rings were shot, though i dunno to be honest)... little blow-by apparant when the oil filler is removed and nothing spraying out of the dipstick hole, so again i'm not thinking it's the rings (or maybe i'm just hoping it isn't!)...

      Last service was only a few months back, the car's not in constant use either - weekends mostly, though it is started midweek. last service was while sorting out an electrical fault (bad wiring to the starter and alternator) and all the ignition components were replaced with new - points, rotor, plugs, cap, condensor, coil, ballast resistor etc etc etc.

      Fuel consumption is pretty normal when it's running on all four cylinders btw.


      • #4

        Foxed me a bit though you won't be too surprised to learn that the biggest damage you can do to you car is just run it on short journeys.

        This is because the car is not running to the peak of its performance capability. Have you ever driven down the road and noticed that the car in front of you has water dripping from the exhaust pipe ? The reason for this is condensation and this causes dramatic damage to the exhaust system by eroding the metal from the inside.

        You take your vehicle on a longer journey (say thirty mile round trip per day or even every couple of days a week) and your car will be running at max capacity and the engine will be happy. You should never thrash your car or push it over 4 tho rpm until the temp gauge has hit normal. This is because the oil is thicker and not running and lubricating the engine and associated parts as quickly as it should.

        I am wondering if you could check on the oil level in the engine. I know people can get a bit carried away and overfill the engine with oil (the dipstick should not display any oil over the maximum mark). If the oil is over drain it off (save it in another container if you must but drain it away). The ideal should be between the halfway and max mark.

        I don't think its a gasket problem, I think its fairly straight forward. It might just be that its standing idle and used little. Once you have had a look at it, it might be worth taking it on a burn out and see how it runs afterwards. You should find that tickover will see an improvement. Don't go on the burn though until you have crossed checked some of the above cause I don't want you breaking down and chucking a piston.


        • #5
          I'm starting to wonder myself Scooby... compression test last night using one of those testers that you have to press and hold against the plug hole, haynes manual says 8-11 bar is normal and the wear limit is 6 bar, so i was expecting to find #4 very low if it is definately oil fouling... the results were - 11 bar on #1 & #2 cylinders and 9 bar on #3 & #4 - but bear in mind i was struggling to get my hands into a restricted space so may not have had a firm enough pressure on the last two.. even so they read fine as far as the rings go...

          pulling all four plugs, they're all quite dark but if the rings are fine then i'm wondering if she's running stupidly rich and in all honesty i'm getting less convinced that #4 is fouling enough for that to cause the problem, it's wet when i pull it, but not dripping wet with oil... Tonite I think i'll back track a bit and check the points, cap and rotor arm again (though they were all new in May and looked okay the other day)...


          • #6
            Don't know too much about the car engine

            But, when I had an old banger ages back, I remember the oil 'flecking' with white spots when the head gasket was going, going, gone!

            Any of that with yours Wile-E? :drive:


            • #7
              That smilie's sooo scary, it looks very similar to someone I know. :lol:

              Ca't help with your car query Wile-E, I know nothing.


              • #8
                You know, sometimes it just pays to start all over again from scratch... the problem was rectified via £1.65 of part and I feel like a complete gimp...

                When the problem started I identified #4 as the problem cylinder.. changed the plug for a spare i had and replaced the HT lead.. no different... the plug was coming out dark and wet.. hence the line of investigation went all over the place...

                I convinced myself that the plug couldnt be fouled enough to stop it sparking, so last nigth i went in from scratch... plugs back in and fired up - 3 cylinders. injectors out to confirm fuel flow - no probs... new points in - 3 cylinders... back to basics and decided to re-confirm the cylinder was #4 - pulled the lead of 4 and she dropped to 2 cylinders... huh?!!! tried #3 & #2 both times down to 2 cylinders... that left #1 and naturally when i pulled the lead it made no difference...

                The lightbulb started to flicker on above my head... now at this point you need to know that i was using "Beru" spark plugs and the spare one i put in was a "Bosch" that i'd kept the last time i changed the plugs (because she was misfiring a bit)... i pulled the plug out of #1 - yes, it was the Bosch.... can you see what's coming yet? i put the original Beru back in - 3 cylinders... damn. I shot down to the car shop and got another plug then put it in... 4 cylinders and sounding sweet as ever.

                Kill me please. :banghead:

                Redwitch is now calling me "Sparky" :badmood:

                I'm guessing both the plugs were giving a weak spark when cleaned, then as they heated up were failing and getting slightly carbonised and wet (hence the dark wet look).... Still, one feels somewhat silly.


                • #9
                  I haven't a clue what you're talking about, but Well Done :lol:


                  • #10
                    Originally posted by Wile-E@Aug 21 2003, 8:07 AM

                    You know, sometimes it just pays to start all over again from scratch... the problem was rectified via £1.65 of part and I feel like a complete gimp...
                    I did that once with the car engine running to hear what would be the possible problem, dropped the leads on and off etc, nearly zapped myself in the process! :lol: Avoided it, just!

                    Nice one though! Just think you could have paid some mechanic to draw breath through their teeth, (at least a hundred quid) for that pleasure!

                    (Apologies to all great mechanics out there too!)


                    • #11
                      Excellent job. Nope I don't think you are a gimp at all. Things happen and cars go wrong. Certain parts will not marry different manufacturers parts.

                      The good news is that it has saved you a big bill for sure.

                      Don't forget though to take it on a run out. You will find that it will do the old girl a world of good and blast some cobwebs away.