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MG Midget and Sprite Technical - A salutory lesson

Just a few lines of experience to impart to others.

For well over a month the car seemed to be misfiring, lacking in power and generally not running as well as it ought to.

Regardless of this, I replaced coil, leads, plugs, adjusted tappets, new oil, filters, all the usual things. Car still down on power and running hot, so changed coolant, made many adjustments to carbs, cleaned all innards out thoroughly etc etc etc ---to no avail.

Short discussion with freindly garage guy earlier this morning when car was in for a gearbox oil darin/top up. He mentioned plugs - to which I repleid they were brand new NGKs about 3 weeks ago, but yes no 2 seemed to be a slightly different shade to the other 3. He ummed and ahhhed, and suggested I do a compression test and possibly change the plug for the old ones - if I still had them.

Doing the easy thing first, I swapped out the plug on no 2 - et voila! Short test run revealed the missing 25% of power - may the patron saint of garages be praised!

I have to say I have never ever come across a duff new plug, but I guess the the moral is never assume all the plugs are OK..even when new!

Mildly annoyed that weeks of tinkering was all in vain, but I have aquired a good knowledge of the engine and at least it is not a head off job!


Mark O

Congrats!!!...i think hahaha

Id call china and demand that 8 year old little girl that made your spark plugs for 26 pennies an hour be severally dealt with....just because she is not allowed to go to school and must work 14 hout days is no excuse for shoddy work

Something else to watch out for thats a huge problem...spark plug temp ranges...alot of the minume wage children that are now parts experts and professionals at the big box parts stores have no clue that there are several tempature ranges fir each spark plug...so if they are out of the one thats needed they they go to the next alt. Not knowing why. Other then thats what the computer screen says

Prop
Prop and the Blackhole Midget

there was a thread about how rare it was to have a faulty new plug

an extract of notes I made, like you learnt mostly by personal experience which can be costly in time, hassle and money

• when the parts, components or fixings arrive check they are correct, not broken and will fit (as much as is possible)
• never assume a new part, component or fixing will not be faulty, some recent new parts have been of poor quality or faulty including rubber products like hoses, electrical items like indicator units, brake light switches, CB points, condensors and rotor arms
• never assume the parts, components and fixings on your car are the original or correct type or fitted correctly or working fully or correctly
Nigel Atkins

precis to 'never assume'
David Smith

In fairness, it is not entirely unreasonable to expect brand new plugs to fire!

Mark O

similar to;

RtFM

test the tester before every test

check the bleeding obvious first (fine when you know what the obvious is)

do logical step by step diagnostics

but all these thinks flee from your mind when you're in the middle of the job

Mark, all those things you done helped with if not resolved your problem and probably need doing sooner rather than later on a car new to you

I had a NOS plug get a slight crack soon after i put it it, with my eyes I didn't notice it

also even though plugs look fine in time and use they do go passed their best, although some seem to believe if they look good then their life is almost infinite :)

as usual a smile inducing post from Prop, I'm sure most would make agreat collection in a book, and to think we get them for free

ETA: again you posted as I was typing, you're assuming again, and having a look at the plugs I'm sure would have been suggested (only vaguely or in a catch-all way by me though)
Nigel Atkins

Mark, 'these days' is the difference - see this all the time. I had exactly the same with a Porsche 924 race car a few months ago - new set of plugs, one was duff.
David Smith

Its not uncommon I know lots of people including myself that have changed to 'new' plugs and then devloped misfires. If you speak to the classic bike boys they know all to well how hit and miss modern plugs are, they only have one cylinder and one plug so the problem shows up pretty quickly. I also think the modern unleaded doesn't help much we never seemed to have the problem with 4 star leaded fuels.
Personally I've found NGK to be more relaible than the rest but I've had dud's from them too.
Ed H

Agree with Ed, I my experience NGK's have fewer problems. Getting my local vendor to carry the proper heat range plug is my problem, so I try to keep a spare set on the bench (when I find them).


Nigel,

Shouldn't be long before Prop becomes a special invited guest at our club shows, and meetings. He could play opposite John Twist (University Motors) during his (excellent) trouble shooting sessions!

Regards,

Larry C.
Larry C '69 Midget

Ed,
Interesting stuff I wonder whether it’s a batch, month or year thing, or less quality testing, or aging machinery

Larry,
I think Prop needs a selected audience to play to solo !
When I saw Prop’s video in which he turned the camera towards himself his image wasn’t a disappointment and fitted his posts – one of life’s pleasures that’s Prop
Nigel Atkins

This thread was discussed between 17/09/2012 and 18/09/2012

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