Discussion
After 2 years trouble free motoring, the racing car has mysteriously developed a missfire, there is no popping or backfire, it just suddenly stopped firing on i think Cyl#3 front N/s i took out the plug
(with some difficulty) and had the engine turn over without any great spark showing, so is it a new set of HT leads,
It has recently returned from a lenghty pit stop of about 6 weeks, prior to which it ran V smoothly
(with some difficulty) and had the engine turn over without any great spark showing, so is it a new set of HT leads,
It has recently returned from a lenghty pit stop of about 6 weeks, prior to which it ran V smoothly
Rich - just caught up with my mails and PH.
My problem was fuel related, I had a miss at idle which gradually got worse. I identified which cylinder by pulling each plug lead whilst the engine was running.
I then swapped bits, plug leads, plugs etc with another cylinder to see if the problem moved. I was getting a healthy spark if I put a spare plug on the suspect lead whilst the engine was running (don't try this without all the plugs fitted - spark and unburnt fuel - say no more!).
If you don't find anything you can try swapping fuel injectors and see if the problem moves.
Let me know if you still can't track it down, and I will tell you what I checked next.
Danny
My problem was fuel related, I had a miss at idle which gradually got worse. I identified which cylinder by pulling each plug lead whilst the engine was running.
I then swapped bits, plug leads, plugs etc with another cylinder to see if the problem moved. I was getting a healthy spark if I put a spare plug on the suspect lead whilst the engine was running (don't try this without all the plugs fitted - spark and unburnt fuel - say no more!).
If you don't find anything you can try swapping fuel injectors and see if the problem moves.
Let me know if you still can't track it down, and I will tell you what I checked next.
Danny
both good suggestions, here is up-date, problem originally appeared to be on cyl3 but now i think its cyl 5 popped plug out had the engine cranked over, but no apparent spark against engine block, plugs are less than 10K old so suspect failed HT lead am looking into price for complete set with German Swedish. have looked at rotor arm bit grubby so cleaned it up, no difference, this is what happens with lengthy pit-stops no way am i parking this up over winter
Ps posted to Rennlist might be worth a try eh
>> Edited by rich 36 on Sunday 13th July 19:34
Ps posted to Rennlist might be worth a try eh
>> Edited by rich 36 on Sunday 13th July 19:34
Right after my visit to Spanners on Thursday, he feels problem is more fuel injection (uh oh)
than leads/plugs etc, seemed reluctant to simply change leads about, so i've been on to Douglass valley who have a set of leads to fit at a fraction of cost of new, so will try that next week, I was always taught to start with the most basic faults first, and not reach for the chequebook to solve everything, some people seem to judge you by your wheels, and charge accordingly WHICH IS WRONG
than leads/plugs etc, seemed reluctant to simply change leads about, so i've been on to Douglass valley who have a set of leads to fit at a fraction of cost of new, so will try that next week, I was always taught to start with the most basic faults first, and not reach for the chequebook to solve everything, some people seem to judge you by your wheels, and charge accordingly WHICH IS WRONG
rich, why dont you swap side to side( use other bank) I have an sc and although ive never taken any bits off, i think one lead must fit for you to test the missfire. If not then take one off another car, doesn't have to be a porsche, just something with normal ht leads as the sc doesn't use anything flash. Good luck
EW, lead on Cyl1 (lhd 1st) is the shortest lead on the car and won't reach any other plug, and no, like you i thought any other lead would do, so scrap yard sol me a long connector'ed vauxhall lead (nothing else will reach that far into cylinder head) but got it home to discover, terminals are not the same at all Bahhh
Sorry guys......but just trying to fit any ignition lead, even from a 16V motor will not do! I've been there and have tried that!
The leads are different in length,and have deep spark plug shrouds!!! they are also individually earthed.
On my car, I found that the plug shroud had perished significantly on No3 cylinder, and was shorting out against the engine bay connections / fuel lines.
this is only visible when dark, but you can hear a characteristic "click" when the misfire occurs on idle.
Decent leads / connections are the only answer here!
I hope this helps.
Leszek.
The leads are different in length,and have deep spark plug shrouds!!! they are also individually earthed.
On my car, I found that the plug shroud had perished significantly on No3 cylinder, and was shorting out against the engine bay connections / fuel lines.
this is only visible when dark, but you can hear a characteristic "click" when the misfire occurs on idle.
Decent leads / connections are the only answer here!
I hope this helps.
Leszek.
Leszek, tried spotting sparks after dark, but couldent' see anything this time, as you quite rightly say, not any lead will do, as the plug tips, are so far in the head,(about 4 1/2" deep) needs something a bit specialised, i'm getting the one lead off it today after running it round the block with lead actually off plug, (it sounds/goes just the same, connected,) and take it to match a replacement, if i find one and it does the trick, i'll be on to porschapart on monday for a whole set £70 BTW =Right picked up a spare lead from v helpfull shop (Sheltune) and popped that on, it still miss-fires, this sounds a bit more involved unfortunately
>> Edited by rich 36 on Saturday 26th July 18:13
>> Edited by rich 36 on Saturday 26th July 18:13
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