← Back to list

2002 Chevy Cavalier Z24 P0300: Engine Sputters, Loss of Power, Smoke and Wet Spark Plugs - Diagnosis and Fix

Model: 2002 Chevy Cavalier z24 Fault Code: P0300 Posted: 2009-01-16 11:17

I own a 2001 Chevrolet Cavalier Z24 with a 2002 Z24 engine. While driving, I noticed the RPMs fluctuating significantly at a stoplight—rising and then dropping unexpectedly. As I continued driving, the vehicle lost power severely (only able to maintain 30 mph on a small incline), exhibiting noticeable sputtering and hesitation, as if running out of fuel. When idling, the engine shakes violently and stutters when accelerating. After parking, I returned minutes later and observed smoke inside the cabin—smelling like gasoline. With the hood open, I saw visible smoke emanating from the engine compartment, again with a gas-like odor. Upon removing the spark plugs, they were heavily soaked in fuel. This led me to suspect either a faulty fuel pressure sensor or an over-fueling condition causing misfires. Could excessive fuel delivery be preventing proper spark ignition? Nashoba

Related fault codes
P0300
Comments (7)
Anonymous 2009-01-16 11:33

The spark plugs I removed are relatively new and show only slight blackening, which suggests incomplete combustion rather than severe fouling.

Anonymous 2009-01-16 14:50

A failing fuel pressure regulator is a likely culprit. Disconnect the vacuum hose from the regulator—if fuel flows out of it, the regulator is defective. If no fuel comes out, crank the engine over and check for fuel discharge from the regulator. If fuel emerges, the regulator is faulty. Additionally, if spark plugs are wet with fuel, they may fail to ignite properly.

Anonymous 2009-01-17 18:21

I disconnected the vacuum hose from the fuel pressure regulator and observed no fuel flow. I repeated the test with the engine running—still no fuel came out of the hose. This suggests either a clogged regulator or an issue in the fuel delivery system. However, the car starts smoothly without difficulty.

Anonymous 2009-01-20 18:09

Next, inspect for stuck-open fuel injectors, which can cause excessive fuel delivery and lead to misfires and poor engine performance.

Anonymous 2009-01-21 09:31

Check the fuel pressure, fuel flow rate, and ensure proper pressure drainage when the engine is off—these are key indicators of a failing fuel system or regulator.

Anonymous 2009-01-21 09:31

Also verify the MAP sensor PID reading at idle to confirm if the engine control unit is receiving accurate intake pressure data, which may affect fuel delivery and ignition timing.

Anonymous 2009-01-21 10:20

Thank you for all the suggestions. The issue was ultimately a faulty ignition coil. I noticed that spark plugs #1 and #4 were particularly wet. After swapping coils between cylinders (replacing coil 1 with coil 2, and vice versa), I observed that plugs #1 and #4 became dry while plugs #2 and #3 remained wet. This confirmed the problem was in the ignition system. Replacing the faulty coil resolved the issue completely—now the car runs smoothly.