← Back to list

2000 GMC Jimmy P0300 Code: How to Fix Rough Idle and Starting Issues

Model: 2000 GMC Jimmy Fault Code: P0300 Posted: 2015-03-22 02:18

I own a 2000 GMC Jimmy that has been throwing up a P0300 diagnostic trouble code. The vehicle starts only when I give it gas, and once running, it idles roughly. I've already replaced the distributor cap, rotor, and inline fuel filter. Notably, the engine runs smoother in neutral compared to drive or park. I'm looking for affordable troubleshooting steps since I've had consistent issues with all my previous vehicles. If it weren't for bad luck, I'd have better success—thank you in advance for any advice. Key questions: Are there any other diagnostic codes? What about fuel pressure and vacuum leaks? How do the spark plugs look (wet, dry, black, tan)? And when removed, are all cylinders firing equally? If replacing spark plugs is needed, I'm advised to use only AC Delco brand plugs for optimal compatibility and performance.

Related fault codes

P0300

Comments (3)

Anonymous 2015-03-22 09:20

No other error codes or additional symptoms? Check fuel pressure and perform a pressure leak-down test—gauges are often available for rent at auto parts stores. Also, conduct a vacuum leak check using carburetor cleaner spray. Examine spark plug condition: are they wet, dry, black, or tan? When removed, do all cylinders fire evenly? If replacing plugs is necessary, only use AC Delco spark plugs—this brand is recommended for compatibility and reliability.

Anonymous 2015-03-23 01:00

Thanks for the detailed tips—I’ll try all of these during my next day off. No other codes or new issues have appeared. Quick question: Why should I only use AC Delco plugs? Is there a technical reason behind this recommendation?

Anonymous 2015-03-23 08:13

AC Delco is considered a professional-grade choice—specifically designed for GM engines like the 2000 GMC Jimmy. While not always mandatory, it ensures better performance and compatibility with older engine systems.