Hot misfire - Trabant

[Tyre Smoke]

Before I spend loads of money chasing an elusive misfire, please confirm my thinking here.

The Trabant is a simple thing. Two cylinder two stroke engine. One carb and two coils fed by an electronic ignition worked from the crankshaft.

Last summer, having rescued it from a barn, I replaced the plugs (NGK) and leads (silicone) and caps (NGK). I also bought two new coils from ebay. No make, probably Chinese imports.

She starts and drives fine, until about four miles into a journey where she starts chronically missing. I'm thinking coils overheating or breaking down or just generally rubbish coils.

I took the carburettor apart and gave it a clean over the weekend, nothing untoward there, it all looked good.

She also refuses to start when hot, as in, drove her 20 miles on Saturday, stopped in our drive and she point blank refused to fire. Went in, had a cup of tea and she fired up straight away. Also the misfire did come and go a bit in that 20 miles. As in it briefly disappeared and then returned. It would be fair to say that after about four miles it was there 95% of the time. And when you only have 26hp, a misfire is no fun.

It's the coils isn't it?

Any recommendations?

[Clifford Chambers]

Does it miss on both cylinders? Check exhaust temp and plugs. If it's only one swap coils to see if misfire follows.

Do you have a strobe? Is the firing point jumping about?

It could also be the electronic ignition. I had a problem with Boyer ignition, when I took it back I was told it wasn't a problem with the unit. Funny how refitting points cured it.

[Tyre Smoke]

The electronic ignition is known to be bullet proof. Very rare it fails. I'm pretty certain it's one cylinder, otherwise she would grind to a halt.

Until she's fully warm, she runs fine and pulls like a train willing donkey.

[steveo3002]

does point towards coils ...do branded parts exist? alot of the china stuff is dead in the box

[Niglebick]

It is electronic, is it?
Most had 2 sets of points on the end of the crank, which could cause the problems you describe? Only the very late ones, or as an aftermarket extra, had electronic.

[egomeister]

No idea what the setup is on a Trabant, but it sounds similar to a problem I had on previous car. The iginition amplifier was breaking down when hot resulting in a severe misfire and inability to restart until everything had cooled.

[E-bmw]

Agreed, sounds like coil.

Is there a reason you used cheap Chinese cr@p?

My understanding of coil is a coil is a coil is a coil, so unless there is a particular reason just get a good quality pair of new ones from your local parts factor.

[Tyre Smoke]

It's definitely electronic. I can recognise that! It must have been fitted (at great expense) by the owner in the Czech Republic. Even today it's £160.00 to buy.

Yes, please chastise me, I bought cheap from the bay rather than Lucas from my local factors. Why? I have no idea, probably because they were gold anodised and, well, shiny things.

I'm going to stump up £40.00 and buy a pair of Lucas like I should have done in the first place. In fact I might see if I can find the ones I took off which as far as I know worked, and see if that makes a difference initially. I suspect they are quite elderly, so if they prove the fault I'll replace.

[dumfriesdave]

Check your emails Tyre Smoke.

[Tyre Smoke]

Thanks! Can't access the link though, it's timing out.

[GreenV8S]

Tyre Smoke said:

It's the coils isn't it?

Any recommendations?

Try the 'bag of frozen peas' technique to cool the coils down and see whether that helps. If so, there's your problem.

You can also fit a spark passive strobe in line with HT leads so that you get a visual indication of spark strength. There are strobes designed specifically for this which fit between the HT lead and it's distributor tower, or between the lead and plug terminal, or ones with trailing HT leads that you can connect and position wherever you want. Or just use an ordinary cheap rubbish passive timing strobe light. A decent electronic one isn't as good but a cheap passive one is basically just a strobe lamp.

[Tyre Smoke]

Despite ordering two coils, and the invoice showing two, only one turned up. The other is coming first class post so might be here tomorrow.

Either way, I'll fit the one Lucas coil that I have in the morning and have a rummage for one of the old coils that I took off and take her out for a jaunt. If she starts misfiring, I'll swap the coils over and see if that makes a difference.

It can't be anything else, there's no other moving parts!!