Flat spot or poor running on carburettor V8
Annoying rather than dangerous.
Symptoms
Hesitation when accelerating, rough idle or poor fuel economy.
Likely cause
Worn SU carburettor spindles, sticking dampers, unbalanced carbs or vacuum leaks.
Suggested fixes
Listed roughly in the order most owners try them.
- 1
Balance and tune the SU carbs
Use a carb balancer to set idle and mixture on both carbs.
- Difficulty:
- Moderate DIY
- Cost:
- £ (Under about £50 in parts)
- 2
Rebuild the carburettors
Rebuild kits with new spindles and needles restore performance.
- Difficulty:
- Moderate DIY
- Cost:
- ££ (About £50 to £300)
This is general guidance gathered from owner experience and workshop practice, not a substitute for a workshop manual or a qualified mechanic. Costs are rough parts-only guides. Brakes, steering and suspension work affects safety, so if in doubt have it checked professionally.
Related faults
- Fuel systemMedium severity
Air in the fuel or failing lift pump
Engine dies after running a while, hard starting after standing, bubbles in the clear fuel line.
Series I · Series II / IIA · Series III · 90 / 110 / 127 · Defender · 2.25 Diesel, 2.5 Diesel, 2.5 Diesel Turbo, 200Tdi, 300Tdi2 fixes - Fuel systemLow severity
2.25 petrol hard to start when hot
Starts fine cold but struggles to restart after a run, especially in warm weather.
Series II / IIA · Series III · 2.25 Petrol3 fixes