Corsa-B.uk - Vauxhall, Opel and Holden Corsa B Owners Club

I've got a 1.2 L SOHOC X12SZ from 1997 which is running rough / misfiring. It's done around 150 000 km / 90 000 miles.

It starts up fine & without any issues but it is idling irregularly. Also when you're driving around it's got a lack of power while misfiring. It's generally worse at lower RPM & speeds. I changed the plugs (which looked a healthy tan color) but that didn't help. I did the paperclip test to check the engine codes but it came back with no fault. No warning lights are on. The HT leads look solid when I checked 'em.

Thinking about replacing the DIS module and HT leads next. Or should I do something else first?

Right, got it fixed.

It was one of the HT leads which was corroded at the distributor end. Wasn't really that visible until you shone a flashlight down the end of the lead to check it out. Swapped it out for a new set of leads and she's purring like a kitten again.