My car stumbles/misses when accelerating. Is there a fix?

This is usually poor ignition, caused by:

• bad, incorrect, platinum or poorly gapped spark plugs
• bad or loose plug wires
• bad ignition coil
• bad transistor pack

Try swapping each one out until you fix the problem. Testing the components may or may not reveal the problem; many people have had components (especially wires) test ok, but perform badly on the car. Plug wires may also be loose in the coil pack, although they may look fine.

Other possible causes include

• a bad battery connection (or bad battery), leading to poor power to the fuel pump;
• misaligned timing belt;
• excessively high airflow through the 1G MAS, leading to 'missed' counts;
• incorrect routing of the vacuum hoses on the throttle body (there was a mistake in a shop manual somewhere);
• decaying of the ECU capacitors (a must read - go here for details);
• worn camshaft lobes (normally only a possible problem on certain aftermarket parts called Web Cams);
• or (in at least one case) a broken thermostat.

Those with an interest in spark plug theory will enjoy this post about Basic Theory of Spark Plug Operation.