steve m
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| posted on 17/5/04 at 08:23 PM |
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would over charging give a misfire
Hi
I still have a serious misfire, but only at these conditions
car been run for at least five miniutes
misfire only occours over 4000 rpm
if engine speed is reduced to less than 4000 rpm normal driving can be resumed within a couple of miniutes
items that have been changed with zero effects are
plugs
plug leads
dizzy cap and rotor arm
coil
lumention ignition
in fact every thing in the ignition circuit except for the dizzy pick up to lumention box
I now have two fuel pumps that are switchable to both or either, and the float levels on both carbs have been checked several times
also on one failure at about 80 mph today I cut the engine and once stopped !! opened the carbs and both were full of fuel, so I do not suspect a fuel
problem
my reasoning for the overcharging is that on one test today with a lcd multimeter the battery was getting 17.7 volts, for about 1 second
any ideas ?????????
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CairB
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| posted on 17/5/04 at 08:38 PM |
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Steve,
Probably a complete red herring but I once had a similarish problem with my sierra. It turned out to be a small piece of debris that was periodically
blocking the main jet. It only blocked it at higher fuel flow rates.
A cracked dizzy cap also caused similar grief and that was with a new one.
Good luck,
Colin
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Hellfire
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| posted on 17/5/04 at 08:44 PM |
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Daft answer cos I know very little - but is your inlet/exhaust tight?
Sounds like your regulator is faulty if your alternator is charging high. The faster the engine goes the more it will allow through - I'd sort
that pretty quickly - even though it's right at the very upper limit the battery will take (unless it's a lorry battery!  )
I'd say the misfire/overcharging is a coincedence.
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gjn200
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| posted on 17/5/04 at 09:46 PM |
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Dead petrol? Seems to loose its 'bang' very quick these days.
<- Me!
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theconrodkid
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| posted on 17/5/04 at 09:58 PM |
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steve,you are only sposed to have about 14.5 volts,excesive voltage could overheat the coil and cause missfire,cooling down will return it to
normal,try replacing the reg,hold yr hand on the coil,see how hot it gets
[Edited on 17/5/04 by theconrodkid]
who cares who wins
pass the pork pies
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steve m
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| posted on 20/5/04 at 07:22 AM |
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I have now changed my alternater and all of the misfire problems have gone, so just in case any one else has this problem, dont go down the obvious
route of changing everything in the ignition and fuel system !!!
This could also be part of my problem of my mot fail as well,
I now have a much nicer car to drive
steve
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britishtrident
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| posted on 20/5/04 at 02:22 PM |
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Seen it a couple of times a misfire caused by the alternator
First time was due to arcing at the the 3 blade connector causing massive voltage spikes which badly upset a Lucas AB17 ignition amplifier on a Rover
820Sli. --- This sounds very like your problem good idea to make 100% sure these connections are clean secure
Second time was due to low voaltage output causing problems (I think) for the fuel injectors on a Rover Mems MPi system on a 214.
[Edited on 20/5/04 by britishtrident]
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