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Curious Misfire


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#1 JakeJakeJake

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Posted 07 December 2010 - 08:34 PM

I have a 1989 mini 30 with a minisport 1380cc engine, a hif44 and a 45d distributor.

Recently I drove to Cambridge about 50 miles and my car was running really rough, not reving freely not wanting to idle. As the temperature gauge barely budged from the bottom I assumed it was just the cold.

The drive home was worse was misfiring losing power wanting to cut out, got to the point where I had to pull over a call break down :goaway:, he finally arrived and said the timing and points were both out a bit, could see on the dizzy cap where it had been sparking too soon. He said it was far too cold (was -2C, lovely weather to wait for breakdown) to set them up as the engine would never get upto to temp, so he towed me home.

I decided enough was enough with points so fitted electronics ignition and set the timing, this made no difference :D This also included replacing dizzy cap and rotor arm.

Tried new leads, possible slight difference still no where near fixed, also tried a new coil which made no difference.

Car has recently had a new alternator which is giving 14v across the battery when on idle.

Fueling is fine, thought it might be head gasket even though it defiantly sounds ignition based, but is not losing any oil or water. Thought it might be the carb but its not really done many miles from new (about 10k), have also tried various extra earth cables which also made no difference.

So I am tired of throwing money at it to no effect but can't afford to take it to a garage, for this reason I will give whoever helps me solve it a fiver, not much I know but might help you think, can paypal or post a cheque? up to you :D

#2 minidaves

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Posted 07 December 2010 - 08:42 PM

have you checked the fues box, wires from ing switch, and what electric ing system have you fitted because normally you need to change the coil as they operate on a 12v system not the 9v of the balasted system your car would have been fitted with

dave

#3 mini danny

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Posted 07 December 2010 - 08:45 PM

have you checked you havent got a dodgy spark plug

#4 samsfern

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Posted 07 December 2010 - 08:46 PM

have you tried temporary wiring a new 12v feed to the coil, maybe off the starter motor solenoid temporarily, to eliminate the ballasted wire, which i never have any joy with. the electronic ignition will need a 12v coil feed too.

Edited by samsfern, 07 December 2010 - 08:46 PM.


#5 1984mini25

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Posted 07 December 2010 - 08:46 PM

Is it jus running like crap at idle and once it’s held a medium ish revs it clears it’s self?

Could just be as it’s cold and damp out; try blocking off the grill to keep the engine bay temp up and see if that helps.

#6 JakeJakeJake

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Posted 07 December 2010 - 08:48 PM

have you checked the fues box, wires from ing switch, and what electric ing system have you fitted because normally you need to change the coil as they operate on a 12v system not the 9v of the balasted system your car would have been fitted with

dave


I wired the electronic ignition upto 12v off the fuse box, like this
Posted Image
from http://mgbreakers.co...cusparkwire.htm

The problem started before electronic ignition was fitted anyway

Edited by JakeJakeJake, 07 December 2010 - 08:49 PM.


#7 Southy

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Posted 07 December 2010 - 08:51 PM

Right first of all don't dismiss the HG being gone, you don't need to loose oil/water for it to of gone, as with 1380's they are prone to blowing across 2 and 3. I would carry out a compression test on the car and see what the results are.

Does the missfire go once the rev's have pickup up/come on cam?I had a missfire issue on my 1380 was really bad before the cam kicked in but once it had come on cam it was fine.Turned out to be a plug kept dropping.

Edited by Southy, 07 December 2010 - 08:52 PM.


#8 JakeJakeJake

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Posted 07 December 2010 - 08:52 PM

have you checked you havent got a dodgy spark plug


Yup checked all the plugs, no luck


have you tried temporary wiring a new 12v feed to the coil, maybe off the starter motor solenoid temporarily, to eliminate the ballasted wire, which i never have any joy with. the electronic ignition will need a 12v coil feed too.


Electronic ignition is wired to 12v, won't hurt to try wiring coil to 12v

The problem started before electronic ignition was fitted

Is it jus running like crap at idle and once it’s held a medium ish revs it clears it’s self?

Could just be as it’s cold and damp out; try blocking off the grill to keep the engine bay temp up and see if that helps.


Nope all revs are terrible, is not too bad at a constant rev if I can keep it there, but nowhere near driveable.

Is in the garage at the moment will not idle or rev really.

#9 samsfern

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Posted 07 December 2010 - 08:53 PM

is it running on all 4? with the engine running, take the ht lead of a spark plug and listen for a change in the engine note, reconnect it and try with the other leads, if the engine note changes that means its firing on that cylinder and obviously if no change is heard, its not firing on the cylinder. if the engine note dont change when you unplug spark plugs 2 and 3, chances are itll be headgasket.
if the headgasket had gone it wouldnt neccessarily lose/burn water or oil, they normally go accross cylinders 2 and 3, a compression test will comfirm this. id be swaying towards a headgasket.

Edited by samsfern, 07 December 2010 - 08:55 PM.


#10 JakeJakeJake

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Posted 07 December 2010 - 08:55 PM

Right first of all don't dismiss the HG being gone, you don't need to loose oil/water for it to of gone, as with 1380's they are prone to blowing across 2 and 3. I would carry out a compression test on the car and see what the results are.

Does the missfire go once the rev's have pickup up/come on cam?I had a missfire issue on my 1380 was really bad before the cam kicked in but once it had come on cam it was fine.Turned out to be a plug kept dropping.


Compression test was next on my to do list, need to find someone with a tester or buy one.

It is really erratic, on and off cam does not seem to make a noticeable difference.

I have tried new plugs

#11 JakeJakeJake

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Posted 07 December 2010 - 08:59 PM

is it running on all 4? with the engine running, take the ht lead of a spark plug and listen for a change in the engine note, reconnect it and try with the other leads, if the engine note changes that means its firing on that cylinder and obviously if no change is heard, its not firing on the cylinder. if the engine note dont change when you unplug spark plugs 2 and 3, chances are itll be headgasket.
if the headgasket had gone it wouldnt neccessarily lose/burn water or oil, they normally go accross cylinders 2 and 3, a compression test will comfirm this. id be swaying towards a headgasket.


Think so all seem to make a difference, but number 4 seemed to make a bigger difference, is hard to tell if the note changes as it will not really hold a steady rev speed.

compression test will be what I do next, what should I be looking for idealy?

#12 Msmith3327

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Posted 07 December 2010 - 08:59 PM

Had the same sort of issue, crap idle and trouble picking up power and cutting out, after doing everything you did it turned out to be the breather pipe from the crank to the carb being all soft and loose, worth a try.

#13 Southy

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Posted 07 December 2010 - 09:00 PM

My thoughts now would be with the HG, If you was closer I would come and test if for you, I'm sure somebody will be able to help you out.

#14 Southy

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Posted 07 December 2010 - 09:01 PM

Compression tests results should be something like 220psi on 4, 20psi on 3 and 2 and 220psi on 1, these was the figures on my engine when mine went.

IE a very large noticeable difference in the figures from 2and3 to the others

Edited by Southy, 07 December 2010 - 09:02 PM.


#15 JakeJakeJake

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Posted 07 December 2010 - 09:04 PM

Had the same sort of issue, crap idle and trouble picking up power and cutting out, after doing everything you did it turned out to be the breather pipe from the crank to the carb being all soft and loose, worth a try.


Crank case just has a breather on it, this part of carb is blanked off

My thoughts now would be with the HG, If you was closer I would come and test if for you, I'm sure somebody will be able to help you out.


Cheers, I will put a post up in the local forums in a minute, hopefully someone local can give me a hand




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