P0304 Fault on 2000 Nissan Altima SE: Can a Vacuum Leak Be Pinpointed and Is $75-1000 Repair Cost Reasonable?
I've been experiencing the 'Service Engine Soon' warning light for several days, which my Nissan dealer has diagnosed as P0304. They believe this is caused by a vacuum leak from the intake manifold gasket and have estimated a repair cost of $750. My main questions are: Can the technician accurately pinpoint the root cause? I understand that P0304 can stem from multiple issues, not just a leaking gasket. Is $750 a fair price for this repair? How much would a local mechanic likely charge me? I've heard about compression testing—how can I perform this myself? What tools and steps are required to do it at home? Any advice on how to verify the issue without going to a dealership would be greatly appreciated.
I've replaced intake manifold gaskets on numerous 2000 Nissan Altima SE models and am confident that a vacuum leak is a common cause of the P0304 code. However, it's important to note that this code can also result from other issues such as faulty spark plugs, ignition coils, or fuel injectors—so it's not always due to the intake gasket. To identify a vacuum leak, you can use carburetor cleaner and spray it along the intake manifold area. If the idle becomes smoother when sprayed over a specific spot, that indicates a leak. A vacuum gauge can also help detect fluctuations in pressure during this test. In many cases, the intake gasket develops cracks or distortion near cylinder #4, which leads to a noticeable rough idle—especially under light load conditions. The car may run fine at higher speeds but feel unstable when idling. I've found that labor costs are typically much lower at independent repair shops compared to dealerships. You should be able to find a reputable local mechanic who can complete the work for significantly less than $750—often in the range of $200–$400 depending on location and shop. I personally don't enjoy doing this repair myself—it's time-consuming, messy, and requires precision. Some mechanics say they’d rather avoid it entirely, while others are comfortable with it. If you're considering a DIY approach, make sure to have the right tools and follow proper procedures. My recommendation: Contact 2–3 local auto shops for written estimates so you can compare pricing and get a second opinion before committing to any repair. This will help ensure you're getting a fair price and accurate diagnosis. Best of luck with your troubleshooting!