← Back to list

2000 Toyota Echo P0300 and P0300 (PD) Random Misfire Issue - Rough Idle When A/C Engages

Model: 2000 Toyota Echo Fault Code: P0300 Posted: 2010-07-11 22:31

I own a 2000 Toyota Echo with 47,000 miles. The car exhibits a slight rough idle when the air conditioning compressor engages. I was advised by the dealership to perform a tune-up, which has been completed. However, the issue persists and approximately three weeks after the service, two diagnostic codes appeared: P0300 (Random Misfire) and P0300 (PD). I'm seeking advice on how to resolve both the rough idle and the persistent misfire code. Note: This vehicle is driven by an 80-year-old woman (my mother), which makes driving conditions quite challenging. Could you please explain what 'PD' means in this context? I've also been wondering if a standard tune-up was sufficient, or whether more comprehensive engine maintenance—such as deep carbon cleaning of the intake valves or fuel injector cleaning—is required given the vehicle's age and low mileage.

Related fault codes
P0300
Comments (2)
Anonymous 2010-07-12 04:50

PD stands for 'Pending' — it means the code was detected but not yet confirmed. Were the correct spark plugs installed during the tune-up? Is there any restriction in the exhaust system, or is it clogged with carbon buildup? Has the engine timing been verified and adjusted correctly?

Anonymous 2010-07-12 08:03

The definition of a 'tune-up' can vary. A 47,000-mile total for a vehicle that's nearly 15 years old suggests it may not be driven frequently enough. Some cars with low mileage due to infrequent use can develop significant carbon deposits and fuel system issues over time. To address rough idle and misfire problems, regular driving — especially under varied conditions — is essential. Simply replacing spark plugs and filters won't resolve deep carbon buildup in the intake valves or varnish accumulation on fuel injectors if the engine isn't run hot enough or for long enough. In such cases, more advanced treatments like professional fuel injector cleaning or upper engine decarbonization may be necessary to restore performance.