Fuel Injectors for 2007–2007 GMC Sierra 2500 HD Classic

How long do injectors last on the 6.0L vs 8.1L Vortec?

The 6.0L LQ4 injectors start failing around 120,000 miles, sometimes sooner if you run cheap gas. The 8.1L L18 injectors hold up better—usually make it to 150,000 before you see problems. Both engines are hard on injectors because of the Vortec fuel pressure cycling. If you tow heavy regularly, expect earlier failure. Replace all eight at once. Mixing old and new injectors causes uneven cylinder fueling and triggers more codes.

Can I replace these injectors myself or do I need a shop?

On the 6.0L it's straightforward. Pull the engine cover, disconnect fuel rails, swap injectors. Takes about three hours with basic tools. The 8.1L is harder—you're fighting for space around that massive block and the fuel rails sit deep. You'll need a fuel line disconnect tool and injector puller. Both engines require depressurizing the fuel system first. Hardest part is the passenger side on either engine because of tight clearance against the firewall.

What codes indicate injector problems on these engines?

P0300 random misfire is the first sign. Then you'll see P0171 and P0174 lean codes as injectors clog or stick. Specific cylinder misfire codes P0301 through P0308 point to individual failed injectors. P0201 through P0208 mean injector circuit faults—check connectors before buying parts. The 6.0L throws P0174 more often on bank 2 because of that passenger side connector corrosion issue. Clear codes, drive 50 miles, see what comes back.

Why does my 8.1L have worse fuel economy after injector replacement?

You probably got injectors with the wrong flow rate. The 8.1L needs 28 lb/hr Multec 2 injectors. Standard 6.0L injectors are 25 lb/hr and won't deliver enough fuel under load. The PCM compensates by increasing injector pulse width, dumping extra fuel. Also check if your new injectors came with updated O-rings. Old-style lower O-rings leak on the 8.1L intake, causing vacuum leaks that throw off fuel trims. Use the green Viton O-rings, not black rubber.