Some help please!

    I took the car out for the first time today since November and experienced a significant misfire. The RHS exhausts are completely sooted and soaking wet with a strong smell of fuel. I pulled all six plugs (1-6) and they are dry but black. I pulled a couple on (7-12) and they appeared normal. At idle, the engine sounds as smooth as normal but the exhausts just emit a strong smell of fuel and a trickle of white smoke. I checked the rotors and leads and all seems OK. Coils were new a few thousand miles ago along with the leads,rotors and plugs.


    Even though the car has sat for a while in a garage it has been regularly started and always, even now with the misfire, starts at first turn of the key. I have never experienced this before and am at a loss to know what it can be, it doesn't feel like limp mode which I have experienced before.:hmmmm:


    Are there any other DIY type diagnostic tests that I can carry out?


    Any guidance would be appreciated.


    Cheers
    Graham

    Hello Graham,


    it is a bit of card reading but you have given a few indicators which in my opinion point towards no spark on the one bank.
    Did you drive the car in this condition or just let it idle?
    What are the temperatures of the exhausts/exhaust gasses? It is sometimes not that easy to detect a non-running bank and one can get fooled by air rushing out of an exhaust despite that part of the engine not firing.


    In case you find one bank out you will probably wish to go the "standard" route of swapping things one by one from the working side to the other and each time check whether the problem moves sides also.


    My first try´d be: start engine and unplug/reconnect AFM´s one after the other.
    Running on all 12 the observation ought to be the same for both AFM´s: slight hesitation upon unplugging which then stabilizes again (unplugged)


    In a condition where only one bank is running you ought to experience two things:
    unplug the AFM of the non-running bank: no change at all
    unplug the AFM of the running bank: likely immediate shutdown, at least massive hesitation and lousy idle


    This ought to allow for a deeper investigation.
    Let us know & good luck.


    @Angus: 12 horses in Graham´s stable ;)


    Reinhard

    Could be a couple of things Nifty....


    1. The Crank Position Sensor has failed for that bank...


    2. There is a fault with the Rotor Arm for that bank...


    A Diagnostics scan should show up the fault but I would say one of those probably....


    Short runs for these V12's are not good as for some reason there is always a build up of condensation in the oil. I bet if you run the engine for a couple of minutes and then check the oil cap you will see white gunky stuff. It will disappear after a long run... I wouldn't worry about the smoke as there is a hell of a lot of exhaust to 'dry' out after being sat.....

    Started car first thing this morning and perfect idle for about 10 minutes then back to problem with dense white smoke coming out of affected side. The exhaust emissions are cool as well compared to the other side so it is definitely a firing problem.


    Removing the MAF plug on the 1-6 bank the engine immediately dies and removal on 7-12 just stabilizes after slight hesitation exactly as you said Reinhard.


    I have also since swapped the coils and this makes no difference so they can be eliminated. I am about to swap the MAF's to eliminate this as well and will report back asap.


    Thanks guys


    Graham

    Hi,


    sorry for your misfortune. Just to be on the safe side, I would double check that the leads go to the right spark plugs. A missfire, in my understanding, is a (at least one possibility) significant timing problem which could be related to measuring the wrong camshaft position by installing the - is it cylinder 1 and 7 or 6 and 12?, well anyway its the leads that to the furthest back in the engine bay on each bank - with the ignition sensor on it to the wrong plug. or any other lead in a wrong positiion might work. Other than that it might be a crank-shaft sensor as stated above or a faulty DME?


    I wish you all the best in finding the culprit.

    Thanks Dieter, the plug leads are all correct but as you say, worth a double check.


    I swapped over the AFM's and got some interesting results. Firstly, the engine was rough but this may have been due to unburnt fuel or clogged plugs. Within a few moments it settled down and I noticed that the identical problem had been transferred to bank 7-12. However, when removing the AFM plugs, neither bank stalled as 1-6 had done before. I removed the AFM from 7-12 seeing as it had transferred the problem and cleaned it with some AFM cleaner. Upon reinstalling, the engine fired up as smooth as ever. I idled out of the garage thinking, problem solved as as soon as I touched the accelerator the misfire came back as bad as ever but on bank 7-12. It would seem to be an AFM problem but short of replacement I am about at my limit of tinkering.:dontknow:


    It is a shame because my car was supposed to go to Refined Detailing today for three weeks while I am away so I had to cancel.:-(


    Cheers
    Graham

    Hi Graham, I have a spare MAF knocking around, do you want me to post it to you? I started my car for the first time since December yesterday and I have a sticking brake caliper. Moral of the story: our cars need driving.

    Zitat von NickF;110188

    Hi Graham, I have a spare MAF knocking around, do you want me to post it to you? I started my car for the first time since December yesterday and I have a sticking brake caliper. Moral of the story: our cars need driving.


    Hi Nick,


    PM sent

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