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1999 Toyota Camry P0300 P0302 P0303 Fault: Check Engine Light Flashes, Codes Recur After Clearing

Model: 1999 Toyota Camry Fault Code: P0300 Posted: 2008-10-23 11:38

I own a 1999 Toyota Camry with 94,000 miles. The car runs smoothly and performs excellently under normal conditions—no hesitation or stalling. However, the check engine light begins flashing intermittently, then turns off, before re-activating in a cycle of flashing and staying on constantly. Every time I clear the fault codes using a Snap-on Solaris scanner, the same three codes—P0300 (Random/Multiple Cylinder Misfire), P0302 (Cylinder 2 Misfire), and P0303 (Cylinder 3 Misfire)—reappear. I've already replaced spark plug wires and installed new OEM Toyota spark plugs. I’ve also tried different engine control units (ECUs), swapped out the coil pack, had the fuel injectors cleaned at Jiffy Lube, and replaced the crankshaft position sensor. A compression test showed 125 psi on all four cylinders—below ideal but consistent. No vacuum leaks were detected, EGR system is functioning properly, and a new timing belt was installed with good gear tooth alignment. Despite these efforts, the P0300/P0302/P0303 codes persist every time I clear them. The engine does not skip or misfire under load—performance remains excellent. What could be causing this persistent fault code despite no visible symptoms? Any insights from experienced Toyota Camry owners or mechanics would be greatly appreciated.

Related fault codes

P0300P0302P0303

Comments (4)

Anonymous 2008-10-23 15:35

This appears to be an intermittent issue, possibly due to a loose, corroded, or damaged electrical connection. I recommend inspecting all wire harness connectors—especially those near the engine and underhood areas—for signs of looseness, physical damage, or contamination. Check if any wires are rubbing against metal surfaces or body panels. This is a common cause in older Toyota models like the 1999 Camry. It's just a hypothesis, but worth investigating.

Anonymous 2008-10-23 16:34

Could you describe when exactly the check engine light starts flashing? Does it occur during steady cruising, deceleration, or acceleration? This timing might help identify whether the misfire is related to load conditions or specific driving patterns.

Anonymous 2008-10-24 19:26

Have you noticed any signs of oil leaking from the valve cover into the spark plug tubes? This is a known issue on certain 1999 Toyota Camry engines, especially with older seals. Oil in the spark plug wells can cause misfires and trigger P0300/P0302/P0303 codes even if the engine runs well otherwise.

Anonymous 2008-10-24 19:51

Did all these symptoms develop after replacing the timing belt? The compression readings (125 psi on all cylinders) are below the expected range—ideally between 150 and 175 psi for a healthy engine. A lower-than-expected compression could indicate internal wear or valve train issues, which may contribute to misfires despite no visible performance loss.