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Stutter; Coil Problem?

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Webb

Webb

Senior Member
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Occassionally when setting off from a stop, my TR6 will cut out once or twice for about the time it takes you to snap your fingers, and then come right back completely normally. The only time it does this is at very low revs, taking off from a stop. It runs without missing a beat once you get past this. And like I said, it only does it once in a while. Anyone had this problem?

I've been suspecting the coil, even though it's less than 6 or 7 years old. Plugs are brand new, points and cap are in good condition, rotor is new. Alternator is about 4 or 5 years old, a good Bosch unit.
 
Just a thought, are you sure you have the right coil on there ? Early TR6 used a "12v" coil with internal ballast, and later ones used a "6v" coil that requires an external ballast resistor. I don't know the transition point offhand, but ISTR it was 71 or 72. Using a "12v" coil with a resistor (which was built into the wiring harness) could cause problems. Ditto a "6v" without the resistor.
 
Yes, the coil is correct. It's a 12v unit, and my car is a 72. It's been driven without any problems for more than 5 years. It's just starting to act up now.
 
My approach to possible ignition problems is the one invented by IBM in the days a big mainframes... I keep a spare of everything and replace stuff one piece at a time until the problem goes away.

Okay, I do try to do basic diagnosis but failing coils, condensors, etc that create intermitent problems do invite this method.

I keep a spare of all ignition components so this at least makes use of them until the day they are put into real service.
 
How old are the ignition wires / leads?
Internal deterioration can give the symptoms you are experiencing.


Pete.
 
Hi Webb....
I think you're on the right track looking at ignition components.
I've had problems before with the condenser by the points (assuming you're running points) which can produce all kind of wierd faults. Try swapping it out before you go onto more complicated solutions.
 
Good call fellas. Yes, I'm running points. Condenser is a good look...I haven't checked that yet. The wires are fairly new; Bosch. They're clean and look to be in good condition. I think they are alright, but if they were old, I would definitly agree with you. It seems to do it more when the engine is hot, and now that it's not burning oil like crazy (engine rebuild round 2) it has been running a bit hotter.
 
The coil is often blamed for faults that lie elsewhere. It's more common for coils to show problems after things under the bonnet have heated up and somewhere well above idle speeds. Start with the cheap stuff such as plugs, points, and condenser and move progressively up the chain. Save coil replacement for last.

You described this problem as the engine "cutting out" as you accelerate from a stop. How do you know it's cutting out? Was the TR6 tach electric or cable driven? (My GT6 is cable driven and therefore I assume yours is also). IF you have an electric tach or if you can temporarily wire one in and place it in the passenger compartment, the electric tach can give a better indication of this problem being ignition related. If you have a coil or distributor related problem an electric tach will immediately drop to zero RPM when/if the engine is actually stopping. If the tach fails to show (i.e. the RPM don't drop to zero) this would indicate that the problem is in the carbs or fuel system. BTW, have you checked the oil in the carb dashpots recently?
 
Especially if they are Bosch. I had several sets of Bosch plug wires and after they broke down prematurely, will never buy another Bosch plug wire again!
 
I've got Webers on it. I really don't believe it was a fuel problem. I've gone through that before and it just doesn't feel like it's losing fuel. Its too abrupt and too quick to have lost fuel. I'll replace the condenser and go from there.
 
I had the same problem that started a while after I replaced the cap, rotor, points, plugs, wires & condenser. The low RPM/high load "miss" got progressively worse and I couldn't find the problem. Finally, after a lot of effort, I took a real close look at the new Lucas dist cap and found the problem. The cap was machined in such a way that the plastic around most of the 6 contacts was higher than the actual contact and was being smeared across the contact face by the rotor. This was leaving a thin layer of dielectric material on the contacts with the expected result.

This was my last straw w/ new Lucas products, even though I try to keep the car as original as possible, I went w/ all Bosch & NGK ignition conponents for driving and keep a nice vintage Lucas setup for the shows.

Good luck.
 
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