Troubleshooting a Rough-Running 1986 Ford Fiesta

When a classic car isn’t running right, the cause isn’t always obvious—but there’s always a reason. This 1986 Ford Fiesta 1100cc came into the workshop with a rough-running engine, and the owner was keen to get it back to full health. What started as a simple check quickly turned into a deeper dive into the heart of the problem.

Step 1: Checking the Basics

The first thing I checked was the firing order, and sure enough, it was incorrect. A quick fix—problem solved, right? Not quite. Even after correcting it, the engine was still misfiring on cylinder one. Time for some deeper investigation.

Step 2: Digging Deeper

Next up was checking the valve clearances, and that’s when things got interesting. One of the valves had no clearance at all, which was a red flag. On closer inspection, I found the real culprit—the top of the valve had broken clean off! At this point, there was only one thing to do: remove the cylinder head and inspect the damage.

Step 3: The Fix & A Lucky Escape

After stripping down the head and checking all the valves, the customer got lucky—there was no further damage beyond the broken valve. A new valve was fitted, and while I was at it, I ground all the valves to ensure a perfect seal and smooth running. Once everything was reassembled, the Fiesta’s engine fired up perfectly, purring like it should.

The Takeaway

A rough-running engine can have many causes, but sometimes the issue runs deeper than expected. Regular maintenance and thorough inspections can prevent small problems from turning into costly repairs. If your classic car isn’t running quite right, don’t ignore it—getting it checked early can save you from a bigger headache down the road!

Got a classic in need of some TLC? Get in touch and let’s get it running like new!