Misfire when hot

[RichG]

Hello my moggy 1098 cc has developed a sort of misfire type symptom when hot , and stuck in traffic , while car is moving along there's no problem , but if I stop in traffic after a short while the tick over becomes lumpy , and when you rev the engine it's all fluffy and misses almost like switching the ignition on and off quickly , iv changed the points and condenser , the cap and rotor arm look like new , iv changed the coil , the leads are all good , iv cleaned out the carb , as was a bit of muck in float chamber , iv reset the carb , and timing , it runs great whilst moving , the problem only occurs when you come to a stand still for a while , then once you can pull away and drive it normally it seems fine again seems to clear out . It seems to be heat related , only happens when hot . Any ideas ? Cos I'm at a loss now !!!!

[bmcecosse]

It's probably having a fit of 'the vapours' - the fuel coming up to the high mounted pump is vapourising in the heat. The pump will be hammering away 19 to the dozen. Some cars do it - others never do it. Some have had success by fitting heat shielding around the fuel pipe - and if you have fitted a 'filter' - take it off. There is a filter in the base of the pump - could be worth removing and cleaning it. The sure-fire remedy is to mount the pump low down - so it has flooded suction from the tank.

[RichG]

Thanx , the pump does seem to start clicking a bit more than usual , it's strange that's it's only just started the last past fortnight, after a run down to Kelmarsh hall , it hiccuped a couple of times when I was on the A 5 , doing about 45 that was under load just as I'd gone round an island , and put my foot back down , it coughed a few times , but nothing major , but it seems to be getting worse now , only when it's. Been idling for a while , you could be rite about the vapour locking tho , sounds very feasible , it won't rev and clear out , it clears after you start driving normal again , and if I leave it ticking over with the bonnet shut for a while when it's warm the tick over goes lumpy and if I hold some revs on , light throttle it's all over the shop , all fluffy and coughing and it pops out the exhaust , it's most strange , so you recon if I make a heat shield around the steel feed pipe , that might help . The pump is located in the usual place up by the battery did you mean move the pump as well ?

[mobylette]

I had the same problem, and fitted the heat shield kit from Mr Grumpy:

http://morrisminorspares.co.uk/shop/pro ... ts_id=3274

No problems since.[frame][/frame]

[RichG]

thanx , any thing is worth a try . il give it ago and see what happens , Thanx again . Richard .

[katy]

mobylette, how about a pic of it installed?

[RichG]

yes i will do .

[whyperion]

Did you correctly fil the dashpot oil?

[mobylette]

Picture of heat shields fitted as requested:[frame][/frame]

[RichG]

thanx for the pics . at least i can see how they are fitted now , sounds like a good idea , a just what i need , keeping fingers crossed lol , thanx again , Richard . il let you know how i get on !!

[katy]

Thanks

[RichG]

have fitted new carb , and what a difference . car is now running like a dream , on closer inspection of the old carb , the butterfly spindle had quite a bit of play in it , and the housing around spindle is worn , so sucking air !! , so a quick road test last night , and all seems ok so far , but i am going to order heat shield kit just be on the safe side , so thanx to all, for your input , much appreciated .!!!!!

[bmcecosse]

You can bush the carb spindle v easily and cheaply.. it only really affects idle slightly.