Having a recurring intermittent problem with 230K+ miler Golf. Runs well most of the time, and will then start missing and finally grind to a halt. Will usually restart then after a few minutes and be fine. Carb has been replaced with reconditioned unit about 30K miles, and all works as it should, so discounting carb icing ?
All ignition components, cap, leads, plugs recently replaced, and all appear Ok. Coil has been on for as long as I can remember, (+ 10 years, +170K miles!)
Coil is a Lucas VW/VAG OE 211 905 115 D, doing a basic test,
Primary Winding Resistance = 1.4 > 1.2 (on 0-200 ohm scale setting)
Secondary Winding Resistance = 2.96 (on 0-200K ohm)
Both of these are outside range specified by Haynes, 0.6-0.8, & 6.9-8.5 respectively (if I've got my readings right)
Is this likely to be a/the problem ?
Any other tests I can carry out?
Any advice much appreciated
Regards
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I wouldn't get too excited about the resistance being out of range.
For the primary, did you correct for the lead resistance, and the contact resistance? (Don't worry about it too much - what you're really looking for is resistance values that are orders of magnitude wrong - these indicate broken wiring, or shorted wiring)
What I would want to do is to make sure that the coil doesn't break down at high voltages - there used to be a simple cheap tool which looked like a plastic pair of compassess which allowed you to see what HT voltage was being produced. Try testing the coil output with one of these when it has just stoped on you. Failing that, just test for a spark just after it has stopped.
I wouldn't necessarily discount carb icing - everything on these installations needs to be right for the carb to work properly - in particular, the hot air feed switch in the air intake needs to be able to pick hot air up from the exhaust manifold region.
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Be a bit cautious with resistance tests; there are several specification differences and a green-label coil should have a secondary resistance of 2400-3500 Ohms. [Other sources suggest a primary resistance range of 0.5-1.5 Ohms.]
Haynes quote the grey-label resistances. [Bosch No. 0 221 122 021]
I'd wonder more about the ignition amplifier or, maybe, the dizzy pick-up than the coil.
Can you definitely confirm that this is an EZ [Not EZA/ABN?] Has it got a cat?
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Thank you both for your replies.
Definately an EZ, non Cat, & with transistor distributor (No CB points)
I think the original Lucas label was green, but now long gone!
Ignition Amplifier ?, pick-up ? Can I test these ?
Removed Coil to test, so corrections shouldn't be necessary ??
I was thinking along the lines of coil failing at high temp - I'll look out for one of those tools, Any idea what it's called ?
I've already checked and replaced all vacuum hose connections etc. to make sure air intake valve working properly etc.
It's my daughters car, RAC came out to her and said "Carbs broken" & towed it back, of course, it's been working fine since, so will probably have to wait till it stops again.
Regards
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To put my post in context, while coils were bolted to the cool, stable inner wing, I found that they were very rarely problematic. I can't remember diagnosing and replacing more than a handful ever.
You're much more likely to have a fault with wiring, either external, or the finer wiring inside the distributor.
Do you know, for a fact, that when the car stops it doesn't have a spark, or it doesn't have fuel. Until you answer that question conclusively, you're guessing, and if you fix it, it will be via luck.
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if this is the engine with a bosch distributor, a simple check to see if amp is working is remove the distributor connector should be a three pin plug, if you place a paper clip into the plug (centre pin marked o, i think !) and remove the king lead from the centre of distributor cap, place the king lead close to an earth/engine block, turn ignition on an briefly stroke the paper clip on a good clean earth you should get a good clean spark from the king lead (mind the spark it hurts) please take all the usuall precautions when doing this ( you can try this when the engine is cold just to prove that it works, then try again when/if if packs up again) as mentioned dont dismiss carb iceing, you need to make sure that the tube from the exhaust to the air filter is okay then you need to check that the thermostatic flap is actually working and not seized i used to go to loads of early cars like this with seized "flaps"
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I agree with topbloke's suggestion - it's almost exactly what I would do. My only variation would be to also stroke the paper clip between the centre pin and the earth pin on the plug, to check that the earth is OK.
However, this test is only useful if you already know that you don't have a spark when the car fails.
To put this together logically;
If the car fails, and you find there's no spark when cranking;
If you then do the test as per topbloke's post and you get a spark
Then look caredully at the distributor / hall effect sensor
If you don't get a spark
Then, look further back in the system, at the 12v supply, the coil, and the amplifier
If the car fails, and you do find a spark when cranking - look carefully at the fuel system.
(Question to mods / developers - why do spaces collapse? I had hoped to indent the IFs as you would when laying out code, but once posted, the indents disappear.)
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Thanks again for your input, I'll check those points again, I'll take it for a long run around the Valleys tomorrow and see what happens. Will post again if I discover anything.
Regards
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Thanks again for your replies, all appreciated. Unfortunately (!) car has behaved perfectly since, starts instantly even when stone cold and damp, idles beautifully at <850rpm, and has done two 150m + journeys in the last week without a hiccup!!
Coming back to the icing theory, the vacuum assisted thermostat on the air intake appears to be working OK, but could it be worn enough to be letting too much cold air in at lower temperatures, rather than the hot air off the exhaust manifold ?
With an air temp of <20degrees C should the flap be 2/3rds open even when idling ?, if so it appears to be only about 25% open, and could therefore be letting in too much cold air ?
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