still got the misfire

garethp6

garethp6

Active Member
hey i have change the engine cause the other was way dead well dieing and i got this misfire i have had the carbs striped and cant find any wear. just put on a new fuel pump and the fuel flow is fine all the leads are plugs have all been change so has the condensor and the points and the coil but it only does it when it worm from cold it fine the only thing is the same from the engine is the distritbur di you think it could be that or somthing else i have got the dwell right and the timming right when it worm and you just revs it up there is no problem only when you drive it any ideas
 
Sounds like you've done all the obvious things. I have two further suggestions. First: run the engine at night somewhere where there are no streetlights. Open the bonnet and look for any evidence of spark tracking. Might be to do with how the plug leads are lying or you might have a duff distributor cap. Either way if there are any problems you should see the blue flashing of the tracking. You often can't see it in daylight or under street lights. Also very carefully inspect the inside of the distrubitor cap for any hints it may be tracking internally. Second: check to see if you have any airleaks on the engine side of the carburettors. These could be on the plastic mounting blocks between the carbs and the manifold or perhaps on the valley gasket between the naifold and the heads. It is possible to fit the wrong one of these - Harvey will tell us which is which no doubt! On the same theme, is the vacuum take off pipe to the distributor intact and sealed? Any hints of anything awry with the servo hose or the performance of the servo?

Chris
 
hi yea there are no air leaks i have check all them and i have change the cab as well i will do that and see it is sparking out. when the engine is worm and ticking over sweet as a nut and when you rev it only misses when you take it for a spin when you got to pull the car away i just ran out of ideas all i can think is the disturbutor it self playing up
 
yea its still like brand new all i am starting to think i hope i got the timing chain right but it would not run as well when it does
 
Have you got a timing light?

If so, what is the timing set at on tickover?

Try disconnecting the vacuum on the distributor (And plugging the pipe) then slowly raise the revs whilst checking the timing.

What is the timing at 2,000 rpm?

Try the same with the vacuum pipe connected and see if there is a difference.

Richard
 
hi yea i have got the light and i have been told to set it TDC cause of the 10.5 plus running on unleaded with the petrol addtivies i am not sure wot is at 2000 rpm as i have not got a rev counter beening the mk1 as i said from cold it lovely but when its get worm then it misfire but not all the time only i can think it might be the disturbotor every thing else have been replaced
 
Hello Gareth,

What brand of spark plugs are you using?

I would follow the excellent advise from Chris and run your engine at night. Take it for a drive and wait till it starts to misfire, then pull over and pop the bonnet. Make sure that you are not near any street
lights. With the engine idling, scan around the engine bay, keeping your hands behind your back. Look closely at all the ignition leads, coil and distributor cap. You may well see the problem!!

An engine misfire especially when at normal operating temperature can often be layed at the feet of either the coil or the distributor leads.

Ron.
 
yea well i got nothing to lose i got the champing L8 1 in it but i did have the later 1's in it and made no differents the coil and leads have been replace but as you said there is no harm in trying i will let you all know when i try it tonight to 2moz
 
Hello Gareth,

Your engine has the P6 heads does it not?

If it does, the spark plugs should be Champion L92YC.

Ron.
 
hi yes it still has got the p6 heads in the book it say to have the L87Y for the early type and the L92Y for the late but i have tryed both and has made no difference with it
 
You are aware the HT leads are meant to be arranged in a special order to stop cross-firing ?
I think you need someone local to give you a second opinion - no disrespect meant but 2 heads are better than one (esp with a V8 !!!!)
 
yea my friend has got 1 as well and he is starting to run out of ideas as he had his p6 since 1975 i have tryed to stop the leads touching each other but some do however i do them has any 1 got any pictures the way they should be set
 
Hello Gareth,

What brand of ignition leads are you using? Cross firing between leads is much less of a problem with the original ignition system,..ie running points. If there is a cross fire, and the leads are arranged as per the original P6B configuration, then between 5 and 7 is the likely problem pair.

What type of ignition coil are you using? Is it a Lucas 16C6 or another type?

Ron.
 
hi 2 be honest i could not tell you wot leads i am using and coil but they have been replaced about 2 times cause i had the missfire but made no difference
 
The pattern for arranging the leads is in the Haynes book and I think the car's handbook. Don't think I know how to scan it to this forum
Ever thought of swapping cap leads rotor condenser etc etc , even carbs and pump from your mate's P6 to save buying new bits needlessly ?
 
yea well i have change the leads about 2 times and the points and the condensor and the coil and its got a brand new fuel pump that just been put on there and the carbs have been striped down and cleaned and checks but all fine plus i had a space set and i have put them on and made no differents i got to say but this car has got people thinking aint it
 
Hello Gareth,

Be sure to take the car out at night and look for any tracking as Chris advised. You won't be able to rule anything in or out until you do.

Ron.
 
yes that my plan next is to try that i hope there is somthing i can i get to the bottom of it only time i can do it now is next week as i aint got the time to do it now
 
Have you used a colour tune to check your mixture?

I had a bit of trouble with rich fueling. root cause was that I had mixed parts from a different spec carb and managed to damage the jet.

have you definatley got the plugs on the correct plug, also a have you got the plugs gap correct? it is easy to drop a plug and the haynes is not the easiest to figure out when it comes to position.

Find plug lead 1 then go clockwise so it should be 1,8,4,3,6,5,7,2 odd cylinders on the right as you look from the front of the engine.

Other things I am wondering about is when the engine had work on it was the timing set correctly? You might need to remove the plug and check that the piston position against the valve being open. Was the camshaft replaced? was it measured? were the followers reused. were the earths all cleaned and reconnected?

If you had a timing light you could put it on each plug in turn and see if there is a pattern to the misfire.

You just got to roll up your sleves until you spot what the problem is.


Colin
 
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