engine surges or misfires while moving

symptom: The engine surges or misfires while moving.

The engine seems to start fine and will normally accelerate fine. As you are driving and maintaining a steady speed, the engine seems to “speed up” slightly or it seems to miss and buck.

Possible causes:

1. If you have a carburetor (there are still a few out there), the choke may not be set properly, or the choke may not be working correctly.

The fix: Check the choke plate and make sure it is opening completely.

2. The engine may be running too hot.

The fix: Check and repair cooling system.

3. The fuel pressure regulator may be operating at low pressure.

The fix: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)

4. The ignition timing may be set wrong.

The fix: Adjust ignition timing.

5. Ignition system problem.

The fix: Check and replace distributor cap, rotor, ignition wires and spark plugs.

6. There may be a fault in the computerised engine control system: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)

7. The fuel filter may be partially clogged.

The fix: Replace the fuel filter.

8. Torque converter (automatic transmission only) may not be locking at the right time, or it may be slipping.

The fix: Check lock up circuit or replace torque converter. (Not a DIY job)

9. There may be a vacuum leak.

The fix: Check and replace vacuum lines as required.

10. Possible internal engine problems.

The fix: Check compression to determine engine condition.

11. EGR valve may be stuck open.

The fix: Replace EGR valve.

12. Drive axles may be loose or worn.

The fix: Check and replace CV/universal joints as required.

13. The fuel injectors may be dirty.

The fix: Clean or replace fuel injectors.