Misfire/miss on cylinders 2.5 V8

[cross]

1964 2.5 V8
Have not experienced this before except for the last two times taking the car out.
Car drives for 12 -15 miles perfectly…. and then after a stop (say for petrol) drives OK for about half a mile and then starts firing on what feels like 2-3 cylinders. Even when given throttle it is a struggle to keep cylinders firing.
If no throttle given i.e. allowing revs to fall to idle the engine will stall and not start again despite trying, for about 8-10 minutes.
When started again, if high throttle is held, the car will fire on most cylinders but if throttle is reduced- then so is the even running - ultimately stalling again.
When in this state the throttle will not respond to increased throttle – if blipped – no response – if steady pressure on throttle no response until ( by judicious "tickling") eventually the revs will rise and firing will even out BUT still not sure all 8 cylinders are firing ! Cannot get above 50mph.
Cannot find anything obvious (loose leads) etc. No reason to suspect dirty petrol. The car has electronic ignition.
First time this happened I had thought it might be fuel starvation due to heat build up. (it was a fairly hot day) but this second time (recently) the day was cold and bright and on both occasions the water temp gauge was normal
Have noticed on overrun down a hill - popping of exhaust (timing ?)
Has anyone got any ideas please

[piman]

Hello Cross,

firstly I'm not familiar with the Daimler engine so my remarks are a generalisation. My first thought is that the mixture is too weak, either through mal adjustment or fuel starvation due to a blockage somewhere. If the latter I would expect the fuel pump to be ticking quite fast (S.U. pump ?), whichever a look at the colour of the plugs should tell you something; if it is lack of fuel they will be quite white. As it does run OK at first (on choke?) it may be attention to the carburettors is the answer?

Alec

[J44EAG]

Could this perhaps also be down to a vapour lock?

I`ve had this symptom when a fuel feed pipe dropped onto a rocket cover and caused a similar effect. Having cable tied the pipe away from the heat source, the problem went away. A classic case of heat soak causing the lock.

Just an idea.

Mike

[cross]

Thanks Piman - will look at the plugs - although I warm the engine in the garage before driving off - so choke is always off when driving
but thanks for your input -I suppose it's possible the engine is overchoked

Mike - will check the routing of the fuel feed pipes - never thought of them "dropping" too close to the rocker covers

Many thanks to you both for your input willl post again when I have had a looksee ( that will be in a couple of Weeks)

[Martec]

Hi,

Have you opened up the carbs to wipe any muck off the carb piston and cylinder. Also is there any oil in the dashpot.

Any muck can stop the piston seating or rising causing problems and acceleration is hit and miss if there is no oil in the dashpots.

Best of luck
Brian

[alec2824]

I have a Daimler V8 and have encountered a similar problem insofar that the car started well and ran for a short time and then refused to accelerate. I changed just about everything -no luck.Then my mate asked if the vacuum advance was working!! I checked by sucking on the end of the lead - sure enough you could see the plate moving slightly. Then he said "poke a wire into the tiny tube that the rubber elbow fits onto." I did, and as if by magic PROBLEM SOLVED. Try it!!! Alec.

[cross]

Thank you gentlemen, for your inputs - much appreciated
Colin

[Buzetti]

Hi Colin, don't know if you have fixed your mis-fire problem yet, but if not, try changing the fuel filter?
If you look at the 'Fuel system' secion of this BB, you will see that I had a similar problem (albeit on an XK motor) - turned out the inside of my fuel tank had rusted and got into the fuel - the filter (in the glass bowl) was badly clogged - new filter cartridge = immediate cure (temporary unfortunately as I still need to fit a new tank for a permanent cure...)
Worth a try?
Cheers
Buzz

[FredS]

Hi,
You probably already have found the problem but, just to further add to the possible causes, my V8 with Lumenition misfires whenever there's oil leaked into the spark plug tubes through the bottom seals there.
Peter Bell tells me this is fairly common with the V8's, so you might find the problem there.
Best of luck,
Fred

[J44EAG]

This is a common issue on the modern AJ 27 series V8 motors as well.

Cam cover seals can be misplaced or disintegrate, flooding spark plug wells with oil and causing misfires. The problem is not just confined to Jaguar V8 units. I had a BMW 530 V8 which suffered the same problem. Water can also enter the plug wells which again can cause ignition misfires.

Mike